PIC18F4455-I/PTG - MICROCHIP TECHNOLOGY

PIC18F2221/2321/4221/4321

Family Data Sheet

Enhanced Flash Microcontrollers with

10-Bit A/D and nanoWatt Technology

Information contained in this publication regarding device

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Trademarks

The Microchip name and logo, the Microchip logo, dsPIC,

KEELOQ, KEELOQ logo, MPLAB, PIC, PICmicro, PICSTART,

rfPIC and UNI/O are registered trademarks of Microchip

Technology Incorporated in the U.S.A. and other countries.

FilterLab, Hampshire, HI-TECH C, Linear Active Thermistor,

MXDEV, MXLAB, SEEVAL and The Embedded Control

Solutions Company are registered trademarks of Microchip

Technology Incorporated in the U.S.A.

Analog-for-the-Digital Age, Application Maestro, CodeGuard,

dsPICDEM, dsPICDEM.net, dsPICworks, dsSPEAK, ECAN,

ECONOMONITOR, FanSense, HI-TIDE, In-Circuit Serial

Programming, ICSP, Mindi, MiWi, MPASM, MPLAB Certified

logo, MPLIB, MPLINK, mTouch, Octopus, Omniscient Code

Generation, PICC, PICC-18, PICDEM, PICDEM.net, PICkit,

PICtail, PIC32 logo, REAL ICE, rfLAB, Select Mode, Total

Endurance, TSHARC, UniWinDriver, WiperLock and ZENA

are trademarks of Microchip Technology Incorporated in the

U.S.A. and other countries.

SQTP is a service mark of Microchip Technology Incorporated

in the U.S.A.

All other trademarks mentioned herein are property of their

respective companies.

Printed on recycled paper.

Note the following details of the code protection feature on Microchip devices:

• Microchip products meet the specification contained in their particular Microchip Data Sheet.

• Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the

intended manner and under normal conditions.

• There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our

knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data

Sheets. Most likely, the person doing so is engaged in theft of intellectual property.

• Microchip is willing to work with the customer who is concerned about the integrity of their code.

• Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not

mean that we are guaranteeing the product as “unbreakable.”

Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our

products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts

allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.

Microchip received ISO/TS-16949:2002 certification for its worldwide

headquarters, design and wafer fabrication facilities in Chandler and

Tempe, Arizona; Gresham, Oregon and design centers in California

and India. The Company’s quality system processes and procedures

are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping

devices, Serial EEPROMs, microperipherals, nonvolatile memory and

analog products. In addition, Microchip’s quality system for the design

and manufacture of development systems is ISO 9001:2000 certified.

PIC18F2221/2321/4221/4321 FAMILY

Power-Managed Modes:

• Run: CPU On, Peripherals On

• Idle: CPU Off, Peripherals On

• Sleep: CPU Off, Peripherals Off

• Idle mode Currents Down to 2.5 μA Typical

• Sleep mode Currents Down to 500 nA Typical

• Timer1 Oscillator: 1.8 μA, 32 kHz, 2V Typical

• Watchdog Timer: 1.6 μA, 2V Typical

• Two-Speed Oscillator Start-up

Flexible Oscillator Structure:

• Four Crystal modes, up to 40 MHz

• 4x Phase Lock Loop (PLL) – Available for Crystal

and Internal Oscillators

• Two External RC modes, up to 4 MHz

• Two External Clock modes, up to 40 MHz

• Internal Oscillator Block:

- 8 user-selectable frequencies, from 31 kHz to

8MHz

- Provides a complete range of clock speeds

from 31 kHz to 32 MHz when used with PLL

- User-tunable to compensate for frequency drift

• Secondary Oscillator using Timer1 @ 32 kHz

• Fail-Safe Clock Monitor

- Allows for safe shutdown if peripheral clock stops

Peripheral Highlights:

• High-Current Sink/Source 25 mA/25 mA

• Three Programmable External Interrupts

• Four Input Change Interrupts

• Up to 2 Capture/Compare/PWM (CCP) modules,

one with Auto-Shutdown (28-pin devices)

• Enhanced Capture/Compare/PWM (ECCP)

module (40/44-pin devices only):

- One, two or four PWM outputs

- Selectable polarity

- Programmable dead time

- Auto-shutdown and auto-restart

Peripheral Highlights (Continued):

• Master Synchronous Serial Port (MSSP) module

Supporting 3-Wire SPI (all 4 modes) and I2C™

Master and Slave modes

• Enhanced Addressable USART module:

- Supports RS-485, RS-232 and LIN/J2602

- Auto-wake-up on Start bit

- Auto-Baud Detect

• 10-Bit, up to 13-Channel Analog-to-Digital

Converter module (A/D):

- Auto-acquisition capability

- Conversion available during Sleep

• Dual Analog Comparators with Input Multiplexing

• Programmable 16-Level High/Low-Voltage

Detection (HLVD) module:

- Supports interrupt on High/Low-Voltage Detection

Special Microcontroller Features:

• C Compiler Optimized Architecture:

- Optional extended instruction set designed to

optimize re-entrant code

• 100,000 Erase/Write Cycle Enhanced Flash

Program Memory Typical

• 1,000,000 Erase/Write Cycle Data EEPROM

Memory Typical

• Flash/Data EEPROM Retention: 100 Years Typical

• Self-Programmable under Software Control

• Priority Levels for Interrupts

• 8 x 8 Single-Cycle Hardware Multiplier

• Extended Watchdog Timer (WDT):

- Programmable period from 4 ms to 131s

• Single-Supply 5V In-Circuit Serial

Programming™ (ICSP™) via Two Pins

• In-Circuit Debug (ICD) via Two Pins

• Wide Operating Voltage Range: 2.0V to 5.5V

• Programmable Brown-out Reset (BOR) with

Software Enable Option)

Device

Program Memory Data Memory

I/O 10-Bit

A/D (ch)

CCP/

ECCP

(PWM)

MSSP

EUSART

Comp. Timers

8/16-Bit

Flash

(bytes)

# Single-Word

Instructions

SRAM

(bytes)

EEPROM

(bytes) SPI Master

I2C™

PIC18F2221 4K 2048 512 256 25 10 2/0 Y Y 1 2 1/3

PIC18F2321 8K 4096 512 256 25 10 2/0 Y Y 1 2 1/3

PIC18F4221 4K 2048 512 256 36 13 1/1 Y Y 1 2 1/3

PIC18F4321 8K 4096 512 256 36 13 1/1 Y Y 1 2 1/3

28/40/44-Pin Enhanced Flash Microcontrollers with

10-Bit A/D and nanoWatt Technology

PIC18F2221/2321/4221/4321 FAMILY

Pin Diagrams

PIC18F2321

14 15

MCLR/VPP/RE3

RA0/AN0

RA1/AN1

RA2/AN2/VREF-/CVREF

RA3/AN3/VREF+

RA4/T0CKI/C1OUT

RA5/AN4/SS/HLVDIN/C2OUT

VSS

OSC1/CLKI/RA7

OSC2/CLKO/RA6

RC0/T1OSO/T13CKI

RC1/T1OSI/CCP2

RC2/CCP1

RC3/SCK/SCL

RB7/KBI3/PGD

RB6//KBI2/PGC

RB5/KBI1/PGM

RB4/KBI0/AN11

RB3/AN9/CCP2

RB2/INT2/AN8

RB1/INT1/AN10

RB0/INT0/FLT0/AN12

VDD

VSS

RC7/RX/DT

RC6/TX/CK

RC5/SDO

RC4/SDI/SDA

28-Pin SPDIP, SOIC, SSOP

PIC18F2221

28-Pin QFN

10 11

12 13 14 15

232425262728

PIC18F2221

RC0/T1OSO/T13CKI

RB7/KBI3/PGD

RB6/KBI2/PGC

RB5/KBI1/PGM

RB4/KBI0/AN11

RB3/AN9/CCP2(1)

RB2/INT2/AN8

RB1/INT1/AN10

RB0/INT0/FLT0/AN12

VDD

VSS

RC7/RX/DT

RC6/TX/CK

RC5/SDO

RC4/SDI/SDA

MCLR/VPP/RE3

RA0/AN0

RA1/AN1

RA2/AN2/VREF-/CVREF

RA3/AN3/VREF+

RA4/T0CKI/C1OUT

RA5/AN4/SS/HLVDIN/C2OUT

VSS

OSC1/CLKI/RA7

OSC2/CLKO/RA6

RC1/T1OSI/CCP2(1)

RC2/CCP1

RC3/SCK/SCL

Note 1: RB3 is the alternate pin for CCP2 multiplexing.

PIC18F2321

PIC18F2221/2321/4221/4321 FAMILY

Pin Diagrams (Continued)

PIC18F4221

RA3/AN3/VREF+

RA2/AN2/VREF-/CVREF

RA1/AN1

RA0/AN0

MCLR/VPP/RE3

RB3/AN9/CCP2(1)

RB7/KBI3/PGD

RB6/KBI2/PGC

RB5/KBI1/PGM

RB4/KBI0/AN11

RC6/TX/CK

RC5/SDO

RC4/SDI/SDA

RD3/PSP3

RD2/PSP2

RD1/PSP1

RD0/PSP0

RC3/SCK/SCL

RC2/CCP1/P1A

RC1/T1OSI/CCP2(1)

RC0/T1OSO/T13CKI

OSC2/CLKO/RA6

OSC1/CLKI/RA7

VSS

VDD

RE2/CS/AN7

RE1/WR/AN6

RE0/RD/AN5

RA5/AN4/SS/HLVDIN/C2OUT

RA4/T0CKI/C1OUT

RC7/RX/DT

RD4/PSP4

RD5/PSP5/P1B

RD6/PSP6/P1C

RD7/PSP7/P1D

VSS

VDD

RB0/INT0/FLT0/AN12

RB1/INT1/AN10

RB2/INT2/AN8

44-Pin QFN(2)

PIC18F4321

Note 1: RB3 is the alternate pin for CCP2 multiplexing.

2: For the QFN package, it is recommended that the bottom pad be connected to VSS.

RB7/KBI3/PGD

RB6/KBI2/PGC

RB5/KBI1/PGM

RB4/KBI0/AN11

RB3/AN9/CCP2

RB2/INT2/AN8

RB1/INT1/AN10

RB0/INT0/FLT0/AN12

VDD

VSS

RD7/PSP7/P1D

RD6/PSP6/P1C

RD5/PSP5/P1B

RD4/PSP4

RC7/RX/DT

RC6/TX/CK

RC5/SDO

RC4/SDI/SDA

RD3/PSP3

RD2/PSP2

MCLR/VPP/RE3

RA0/AN0

RA1/AN1

RA2/AN2/VREF-/CVREF

RA3/AN3/VREF+

RA4/T0CKI/C1OUT

RA5/AN4/SS/HLVDIN/C2OUT

RE0/RD/AN5

RE1/WR/AN6

RE2/CS/AN7

VDD

VSS

OSC1/CLKI/RA7

OSC2/CLKO/RA6

RC0/T1OSO/T13CKI

RC1/T1OSI/CCP2

RC2/CCP1/P1A

RC3/SCK/SCL

RD0/PSP0

RD1/PSP1

PIC18F4321

40-Pin PDIP

PIC18F4221

PIC18F2221/2321/4221/4321 FAMILY

Pin Diagrams (Continued)

PIC18F4221

RA3/AN3/VREF+

RA2/AN2/VREF-/CVREF

RA1/AN1

RA0/AN0

MCLR/VPP/RE3

RB7/KBI3/PGD

RB6/KBI2/PGC

RB5/KBI1/PGM

RB4/KBI0/AN11

RC6/TX/CK

RC5/SDO

RC4/SDI/SDA

RD3/PSP3

RD2/PSP2

RD1/PSP1

RD0/PSP0

RC3/SCK/SCL

RC2/CCP1/P1A

RC1/T1OSI/CCP2(1)

RC0/T1OSO/T13CKI

OSC2/CLKO/RA6

OSC1/CLKI/RA7

VSS

VDD

RE2/CS/AN7

RE1/WR/AN6

RE0/RD/AN5

RA5/AN4/SS/HLVDIN/C2OUT

RA4/T0CKI/C1OUT

RC7/RX/DT

RD4/PSP4

RD5/PSP5/P1B

RD6/PSP6/P1C

RD7/PSP7/P1D

VSS

VDD

RB0/INT0/FLT0/AN12

RB1/INT1/AN10

RB2/INT2/AN8

RB3/AN9/CCP2(1)

44-Pin TQFP

PIC18F4321

Note 1: RB3 is the alternate pin for CCP2 multiplexing.

PIC18F2221/2321/4221/4321 FAMILY

Table of Contents

1.0 Device Overview .......................................................................................................................................................................... 9

2.0 Guidelines for Getting Started with PIC18F Microcontrollers ..................................................................................................... 25

3.0 Oscillator Configurations ............................................................................................................................................................ 29

4.0 Power-Managed Modes ............................................................................................................................................................. 39

5.0 Reset .......................................................................................................................................................................................... 47

6.0 Memory Organization ................................................................................................................................................................. 59

7.0 Flash Program Memory.............................................................................................................................................................. 79

8.0 Data EEPROM Memory ............................................................................................................................................................. 89

9.0 8 x 8 Hardware Multiplier............................................................................................................................................................ 95

10.0 Interrupts .................................................................................................................................................................................... 97

11.0 I/O Ports ................................................................................................................................................................................... 111

12.0 Timer0 Module ......................................................................................................................................................................... 129

13.0 Timer1 Module ......................................................................................................................................................................... 133

14.0 Timer2 Module ......................................................................................................................................................................... 139

15.0 Timer3 Module ......................................................................................................................................................................... 141

16.0 Capture/Compare/PWM (CCP) Modules ................................................................................................................................. 145

17.0 Enhanced Capture/Compare/PWM (ECCP) Module................................................................................................................ 153

18.0 Master Synchronous Serial Port (MSSP) Module .................................................................................................................... 167

19.0 Enhanced Universal Synchronous Asynchronous Receiver Transmitter (EUSART) ............................................................... 211

20.0 10-Bit Analog-to-Digital Converter (A/D) Module ..................................................................................................................... 233

21.0 Comparator Module.................................................................................................................................................................. 243

22.0 Comparator Voltage Reference Module................................................................................................................................... 249

23.0 High/Low-Voltage Detect (HLVD)............................................................................................................................................. 253

24.0 Special Features of the CPU.................................................................................................................................................... 259

25.0 Instruction Set Summary .......................................................................................................................................................... 279

26.0 Development Support............................................................................................................................................................... 329

27.0 Electrical Characteristics.......................................................................................................................................................... 333

28.0 Packaging Information.............................................................................................................................................................. 373

Appendix A: Revision History............................................................................................................................................................. 385

Appendix B: Device Differences ........................................................................................................................................................ 386

Appendix C: Conversion Considerations ........................................................................................................................................... 387

Appendix D: Migration from Baseline to Enhanced Devices.............................................................................................................. 387

Appendix E: Migration From Mid-Range to Enhanced Devices ......................................................................................................... 388

Appendix F: Migration From High-End to Enhanced Devices............................................................................................................ 388

Index ................................................................................................................................................................................................. 389

The Microchip Web Site..................................................................................................................................................................... 399

Customer Change Notification Service .............................................................................................................................................. 399

Customer Support .............................................................................................................................................................................. 399

Reader Response .............................................................................................................................................................................. 400

PIC18F2221/2321/4221/4321 Product Identification System ............................................................................................................ 401

PIC18F2221/2321/4221/4321 FAMILY

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The last character of the literature number is the version number, (e.g., DS30000A is version A of document DS30000).

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To determine if an errata sheet exists for a particular device, please check with one of the following:

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Customer Notification System

PIC18F2221/2321/4221/4321 FAMILY

1.0 DEVICE OVERVIEW

This document contains device specific information for

the following devices:

This family offers the advantages of all PIC18 micro-

controllers – namely, high computational performance at

an economical price – with the addition of high-

endurance, Enhanced Flash program memory. On top of

these features, the PIC18F2221/2321/4221/4321 family

introduces design enhancements that make these micro-

controllers a logical choice for many high-performance,

power sensitive applications.

1.1 New Core Features

1.1.1 nanoWatt TECHNOLOGY

All of the devices in the PIC18F2221/2321/4221/4321

family incorporate a range of features that can signifi-

cantly reduce power consumption during operation.

Key items include:

•Alternate Run Modes: By clocking the controller

from the Timer1 source or the internal oscillator

block, power consumption during code execution

can be reduced by as much as 90%.

•Multiple Idle Modes: The controller can also run

with its CPU core disabled but the peripherals still

active. In these states, power consumption can be

reduced even further, to as little as 4% of normal

operation requirements.

•On-the-Fly Mode Switching: The

power-managed modes are invoked by user code

during operation, allowing the user to incorporate

power-saving ideas into their application’s

software design.

•Low Consumption in Key Modules: The

power requirements for both Timer1 and the

Watchdog Timer are minimized. See

Section 27.0 “Electrical Characteristics” for

values.

1.1.2 MULTIPLE OSCILLATOR OPTIONS

AND FEATURES

All of the devices in the PIC18F2221/2321/4221/4321

family offer ten different oscillator options, allowing

users a wide range of choices in developing application

hardware. These include:

• Four Crystal modes, using crystals or ceramic

resonators.

• Two External Clock modes, offering the option of

using two pins (oscillator input and a divide-by-4

clock output) or one pin (oscillator input, with the

second pin reassigned as general I/O).

• Two External RC Oscillator modes with the same

pin options as the External Clock modes.

• Two Internal Oscillator modes which provide

an 8 MHz clock and an INTRC source

(approximately 31 kHz), as well as a range of

6 user-selectable clock frequencies, between

125 kHz to 4 MHz, for a total of 8 clock frequencies.

One or both of the oscillator pins can be used for

general purpose I/O.

• A Phase Lock Loop (PLL) frequency multiplier,

available to both the high-speed crystal and

internal oscillator modes, which allows clock

speeds of up to 40 MHz. Used with the internal

oscillator, the PLL gives users a complete selection

of clock speeds, from 31 kHz to 32 MHz – all

without using an external crystal or clock circuit.

Besides its availability as a clock source, the internal

oscillator block provides a stable reference source that

gives the family additional features for robust

operation:

•Fail-Safe Clock Monitor: This option constantly

monitors the main clock source against a reference

signal provided by the internal oscillator. If a clock

failure occurs, the controller is switched to the

internal oscillator block, allowing for continued

low-speed operation or a safe application

shutdown.

•Two-Speed Start-up: This option allows the

internal oscillator to serve as the clock source

from Power-on Reset, or wake-up from Sleep

mode, until the primary clock source is available.

• PIC18F2221 • PIC18LF2221

• PIC18F2321 • PIC18LF2321

• PIC18F4221 • PIC18LF4221

• PIC18F4321 • PIC18LF4321

PIC18F2221/2321/4221/4321 FAMILY

1.2 Other Special Features

•Memory Endurance: The Enhanced Flash cells

for both program memory and data EEPROM are

rated to last for many thousands of erase/write

cycles – up to 100,000 for program memory and

1,000,000 for EEPROM. Data retention without

refresh is conservatively estimated to be greater

than 40 years.

•Self-Programmability: These devices can write to

their own program memory spaces under internal

software control. By using a bootloader routine,

located in the protected Boot Block at the top of

program memory, it becomes possible to create an

application that can update itself in the field.

•Extended Instruction Set: The PIC18F2221/

2321/4221/4321 family introduces an optional

extension to the PIC18 instruction set, which adds

8 new instructions and an Indexed Addressing

mode. This extension, enabled as a device con-

figuration option, has been specifically designed

to optimize re-entrant application code originally

developed in high-level languages, such as C.

•Enhanced CCP Module: In PWM mode, this

module provides 1, 2 or 4 modulated outputs for

controlling half-bridge and full-bridge drivers.

Other features include auto-shutdown, for

disabling PWM outputs on interrupt or other select

conditions and auto-restart, to reactivate outputs

once the condition has cleared.

•Enhanced Addressable USART: This serial

communication module is capable of standard

RS-232 operation and provides support for the

LIN/J2602 bus protocol. Other enhancements

include automatic baud rate detection and a 16-bit

Baud Rate Generator for improved resolution.

When the microcontroller is using the internal

oscillator block, the EUSART provides stable

operation for applications that talk to the outside

world without using an external crystal (or its

accompanying power requirement).

•10-Bit A/D Converter: This module incorporates

programmable acquisition time, allowing for a

channel to be selected and a conversion to be

initiated without waiting for a sampling period and

thus, reducing code overhead.

•Extended Watchdog Timer (WDT): This

Enhanced version incorporates a 16-bit prescaler,

allowing an extended time-out range that is stable

across operating voltage and temperature. See

Section 27.0 “Electrical Characteristics” for

time-out periods.

1.3 Details on Individual Family

Members

Devices in the PIC18F2221/2321/4221/4321 family are

available in 28-pin and 40/44-pin packages. Block

diagrams for the two groups are shown in Figure 1-1 and

Figure 1-2.

The devices are differentiated from each other in five

ways:

1. Flash program memory (4 Kbytes for

PIC18F2221/4221 devices, 8 Kbytes for

PIC18F2321/4321).

2. A/D channels (10 for 28-pin devices, 13 for

40/44-pin devices).

3. I/O ports (3 bidirectional ports on 28-pin devices,

5 bidirectional ports on 40/44-pin devices).

4. CCP and Enhanced CCP implementation

(28-pin devices have 2 standard CCP

modules, 40/44-pin devices have one standard

CCP module and one ECCP module).

5. Parallel Slave Port (present only on 40/44-pin

devices).

All other features for devices in this family are identical.

These are summarized in Table 1-1.

The pinouts for all devices are listed in Table 1-2 and

Table 1-3.

Like all Microchip PIC18 devices, members of the

PIC18F2221/2321/4221/4321 family are available as

both standard and low-voltage devices. Standard

devices with Enhanced Flash memory, designated with

an “F” in the part number (such as PIC18F2321),

accommodate an operating VDD range of 4.2V to 5.5V.

Low-voltage parts, designated by “LF” (such as

PIC18LF2321), function over an extended VDD range

of 2.0V to 5.5V.

PIC18F2221/2321/4221/4321 FAMILY

TABLE 1-1: DEVICE FEATURES

Features PIC18F2221 PIC18F2321 PIC18F4221 PIC18F4321

Operating Frequency DC – 40 MHz DC – 40 MHz DC – 40 MHz DC – 40 MHz

Program Memory (Bytes) 4096 8192 4096 8192

Program Memory (Instructions) 2048 4096 2048 4096

Data Memory (Bytes) 512 512 512 512

Data EEPROM Memory (Bytes) 256 256 256 256

Interrupt Sources 19 19 20 20

I/O Ports Ports A, B, C, (E) Ports A, B, C, (E) Ports A, B, C, D, E Ports A, B, C, D, E

Timers 4 4 4 4

Capture/Compare/PWM Modules 2 2 1 1

Enhanced Capture/Compare/

PWM Modules

0011

Serial Communications MSSP,

Enhanced USART

MSSP,

Enhanced USART

MSSP,

Enhanced USART

MSSP,

Enhanced USART

Parallel Communications (PSP) No No Yes Yes

10-bit Analog-to-Digital Module 10 Input Channels 10 Input Channels 13 Input Channels 13 Input Channels

Resets (and Delays) POR, BOR,

RESET Instruction,

Stack Full,

Stack Underflow

(PWRT, OST),

MCLR (optional),

WDT

POR, BOR,

RESET Instruction,

Stack Full,

Stack Underflow

(PWRT, OST),

MCLR (optional),

WDT

POR, BOR,

RESET Instruction,

Stack Full,

Stack Underflow

(PWRT, OST),

MCLR (optional),

WDT

POR, BOR,

RESET Instruction,

Stack Full,

Stack Underflow

(PWRT, OST),

MCLR (optional),

WDT

Programmable Low-Voltage

Detect

Yes Yes Yes Yes

Programmable Brown-out Reset Yes Yes Yes Yes

Instruction Set 75 Instructions;

83 with Extended

Instruction Set

enabled

75 Instructions;

83 with Extended

Instruction Set

enabled

75 Instructions;

83 with Extended

Instruction Set

enabled

75 Instructions;

83 with Extended

Instruction Set

enabled

Packages 28-pin SPDIP

28-pin SOIC

28-pin SSOP

28-pin QFN

28-pin SPDIP

28-pin SOIC

28-pin SSOP

28-pin QFN

40-pin PDIP

44-pin QFN

44-pin TQFP

40-pin PDIP

44-pin QFN

44-pin TQFP

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 1-1: PIC18F2221/2321 (28-PIN) BLOCK DIAGRAM

Instruction

Decode &

Control

PORTA

PORTB

PORTC

RA4/T0CKI/C1OUT

RA5/AN4/SS/HLVDIN/C2OUT

RB0/INT0/FLT0/AN12

RC0/T1OSO/T13CKI

RC1/T1OSI/CCP2(1)

RC2/CCP1

RC3/SCK/SCL

RC4/SDI/SDA

RC5/SDO

RC6/TX/CK

RC7/RX/DT

RA3/AN3/VREF+

RA2/AN2/VREF-/CVREF

RA1/AN1

RA0/AN0

RB1/INT1/AN10

Data Latch

Data Memory

(3.9 Kbytes)

Address Latch

Data Address<12>

Access

BSR FSR0

FSR1

FSR2

inc/dec

logic

Address

412 4

PCH PCL

PCLATH

31 Level Stack

Program Counter

PRODLPRODH

8 x 8 Multiply

BITOP

ALU<8>

Address Latch

Program Memory

(4 Kbytes)

Data Latch

Table Pointer<21>

inc/dec logic

Data Bus<8>

Table Latch

ROM Latch

RB2/INT2/AN8

RB3/AN9/CCP2(1)

PCLATU

PCU

OSC2/CLKO(3)/RA6

Note 1: CCP2 is multiplexed with RC1 when Configuration bit, CCP2MX, is set, or RB3 when CCP2MX is not set.

2: RE3 is only available when MCLR functionality is disabled.

3: OSC1/CLKI and OSC2/CLKO are only available in select oscillator modes and when these pins are not being used as digital I/O.

Refer to Section 3.0 “Oscillator Configurations” for additional information.

RB4/KBI0/AN11

RB5/KBI1/PGM

RB6/KBI2/PGC

RB7/KBI3/PGD

EUSARTComparator MSSP 10-Bit

ADC

Timer2Timer1 Timer3Timer0

CCP2

LVD

CCP1

BOR Data

EEPROM

Instruction Bus <16>

STKPTR Bank

State Machine

Control Signals

Decode

Power-up

Timer

Oscillator

Start-up Timer

Power-on

Reset

Watchdog

Timer

OSC1(3)

OSC2(3)

VDD,

Brown-out

Reset

Internal

Oscillator

Fail-Safe

Clock Monitor

Precision

Reference

Band Gap

VSS

MCLR(2)

Block

INTRC

Oscillator

8 MHz

Oscillator

Single-Supply

Programming

In-Circuit

Debugger

T1OSO

OSC1/CLKI(3)/RA7

T1OSI

PORTE

MCLR/VPP/RE3(2)

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 1-2: PIC18F4221/4321 (40/44-PIN) BLOCK DIAGRAM

Instruction

Decode &

Control

Data Latch

Data Memory

(3.9 Kbytes)

Address Latch

Data Address<12>

Access

BSR FSR0

FSR1

FSR2

inc/dec

logic

Address

412 4

PCH PCL

PCLATH

31 Level Stack

Program Counter

PRODLPRODH

8 x 8 Multiply

BITOP

ALU<8>

Address Latch

Program Memory

(8 Kbytes)

Data Latch

Table Pointer<21>

inc/dec logic

Data Bus<8>

Table Latch

ROM Latch

PORTD

RD0/PSP0

PCLATU

PCU

PORTE

MCLR/VPP/RE3(2)

RE2/CS/AN7

RE0/RD/AN5

RE1/WR/AN6

Note 1: CCP2 is multiplexed with RC1 when Configuration bit, CCP2MX, is set, or RB3 when CCP2MX is not set.

2: RE3 is only available when MCLR functionality is disabled.

3: OSC1/CLKI and OSC2/CLKO are only available in select oscillator modes and when these pins are not being used as digital I/O.

Refer to Section 3.0 “Oscillator Configurations” for additional information.

:RD4/PSP4

EUSARTComparator MSSP 10-Bit

ADC

Timer2Timer1 Timer3Timer0

CCP2

LVD

ECCP1

BOR Data

EEPROM

Instruction Bus <16>

STKPTR Bank

State Machine

Control Signals

Decode

Power-up

Timer

Oscillator

Start-up Timer

Power-on

Reset

Watchdog

Timer

OSC1(3)

OSC2(3)

VDD,

Brown-out

Reset

Internal

Oscillator

Fail-Safe

Clock Monitor

Precision

Reference

Band Gap

VSS

MCLR(2)

Block

INTRC

Oscillator

8 MHz

Oscillator

Single-Supply

Programming

In-Circuit

Debugger

T1OSI

T1OSO

RD5/PSP5/P1B

RD6/PSP6/P1C

RD7/PSP7/P1D

PORTA

PORTB

PORTC

RA4/T0CKI/C1OUT

RA5/AN4/SS/HLVDIN/C2OUT

RB0/INT0/FLT0/AN12

RC0/T1OSO/T13CKI

RC1/T1OSI/CCP2(1)

RC2/CCP1/P1A

RC3/SCK/SCL

RC4/SDI/SDA

RC5/SDO

RC6/TX/CK

RC7/RX/DT

RA3/AN3/VREF+

RA2/AN2/VREF-/CVREF

RA1/AN1

RA0/AN0

RB1/INT1/AN10

RB2/INT2/AN8

RB3/AN9/CCP2(1)

OSC2/CLKO(3)/RA6

RB4/KBI0/AN11

RB5/KBI1/PGM

RB6/KBI2/PGC

RB7/KBI3/PGD

OSC1/CLKI(3)/RA7

PIC18F2221/2321/4221/4321 FAMILY

TABLE 1-2: PIC18F2221/2321 PINOUT I/O DESCRIPTIONS

Pin Name

Pin Number

Type

Buffer

Type Description

SPDIP,

SOIC,

SSOP

QFN

MCLR/VPP/RE3

MCLR

VPP

RE3

126

Master Clear (input) or programming voltage (input).

Master Clear (Reset) input. This pin is an active-low

Reset to the device.

Programming voltage input.

Digital input.

OSC1/CLKI/RA7

OSC1

CLKI

RA7

I/O

Analog

CMOS

TTL

Oscillator crystal or external clock input.

Oscillator crystal input or external clock source input.

ST buffer when configured in RC mode; CMOS otherwise.

External clock source input. Always associated with

pin function OSC1. (See related OSC1/CLKI,

OSC2/CLKO pins.)

General purpose I/O pin.

OSC2/CLKO/RA6

OSC2

CLKO

RA6

10 7

I/O

—

TTL

Oscillator crystal or clock output.

Oscillator crystal output. Connects to crystal or resonator

in Crystal Oscillator mode.

In RC, EC and INTIO modes, OSC2 pin outputs CLKO

which has one-fourth the frequency of OSC1 and denotes

the instruction cycle rate.

General purpose I/O pin.

Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output

ST = Schmitt Trigger input with CMOS levels I = Input P = Power

I2C = ST with I2C™ or SMB levels O = Output

Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.

2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.

PIC18F2221/2321/4221/4321 FAMILY

PORTA is a bidirectional I/O port.

RA0/AN0

RA0

AN0

227

I/O

TTL

Analog

Digital I/O.

Analog Input 0.

RA1/AN1

RA1

AN1

328

I/O

TTL

Analog

Digital I/O.

Analog Input 1.

RA2/AN2/VREF-/CVREF

RA2

AN2

VREF-

CVREF

I/O

TTL

Analog

Digital I/O.

Analog Input 2.

A/D reference voltage (low) input.

Comparator reference voltage output.

RA3/AN3/VREF+

RA3

AN3

VREF+

I/O

TTL

Analog

Digital I/O.

Analog Input 3.

A/D reference voltage (high) input.

RA4/T0CKI/C1OUT

RA4

T0CKI

C1OUT

I/O

—

Digital I/O. Open-collector output.

Timer0 external clock input.

Comparator 1 output.

RA5/AN4/SS/HLVDIN/

C2OUT

RA5

AN4

HLVDIN

C2OUT

I/O

TTL

Analog

TTL

Analog

—

Digital I/O.

Analog Input 4.

SPI slave select input.

High/Low-Voltage Detect input.

Comparator 2 output.

RA6 See the OSC2/CLKO/RA6 pin.

RA7 See the OSC1/CLKI/RA7 pin.

TABLE 1-2: PIC18F2221/2321 PINOUT I/O DESCRIPTIONS (CONTINUED)

Pin Name

Pin Number

Type

Buffer

Type Description

SPDIP,

SOIC,

SSOP

QFN

Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output

ST = Schmitt Trigger input with CMOS levels I = Input P = Power

I2C = ST with I2C™ or SMB levels O = Output

Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.

2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.

PIC18F2221/2321/4221/4321 FAMILY

PORTB is a bidirectional I/O port. PORTB can be software

programmed for internal weak pull-ups on all inputs.

RB0/INT0/FLT0/AN12

RB0

INT0

FLT0

AN12

21 18

I/O

TTL

Analog

Digital I/O.

External Interrupt 0.

PWM Fault input for CCP1.

Analog Input 12.

RB1/INT1/AN10

RB1

INT1

AN10

22 19

I/O

TTL

Analog

Digital I/O.

External Interrupt 1.

Analog Input 10.

RB2/INT2/AN8

RB2

INT2

AN8

23 20

I/O

TTL

Analog

Digital I/O.

External Interrupt 2.

Analog Input 8.

RB3/AN9/CCP2

RB3

AN9

CCP2(2)

24 21

I/O

TTL

Analog

Digital I/O.

Analog Input 9.

Capture 2 input/Compare 2 output/PWM2 output.

RB4/KBI0/AN11

RB4

KBI0

AN11

25 22

I/O

TTL

Analog

Digital I/O.

Interrupt-on-change pin.

Analog Input 11.

RB5/KBI1/PGM

RB5

KBI1

PGM

26 23

I/O

TTL

Digital I/O.

Interrupt-on-change pin.

Low-Voltage ICSP™ programming enable pin.

RB6/KBI2/PGC

RB6

KBI2

PGC

27 24

I/O

TTL

Digital I/O.

Interrupt-on-change pin.

In-circuit debugger and ICSP programming clock pin.

RB7/KBI3/PGD

RB7

KBI3

PGD

28 25

I/O

TTL

Digital I/O.

Interrupt-on-change pin.

In-circuit debugger and ICSP programming data pin.

TABLE 1-2: PIC18F2221/2321 PINOUT I/O DESCRIPTIONS (CONTINUED)

Pin Name

Pin Number

Type

Buffer

Type Description

SPDIP,

SOIC,

SSOP

QFN

Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output

ST = Schmitt Trigger input with CMOS levels I = Input P = Power

I2C = ST with I2C™ or SMB levels O = Output

Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.

2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.

PIC18F2221/2321/4221/4321 FAMILY

PORTC is a bidirectional I/O port.

RC0/T1OSO/T13CKI

RC0

T1OSO

T13CKI

11 8

I/O

—

Digital I/O.

Timer1 oscillator analog output.

Timer1/Timer3 external clock input.

RC1/T1OSI/CCP2

RC1

T1OSI

CCP2(1)

12 9

I/O

Analog

Digital I/O.

Timer1 oscillator analog input.

Capture 2 input/Compare 2 output/PWM2 output.

RC2/CCP1

RC2

CCP1

13 10

I/O

Digital I/O.

Capture 1 input/Compare 1 output/PWM1 output.

RC3/SCK/SCL

RC3

SCK

SCL

14 11

I/O

I2C

Digital I/O.

Synchronous serial clock input/output for SPI mode.

Synchronous serial clock input/output for I2C™ mode.

RC4/SDI/SDA

RC4

SDI

SDA

15 12

I/O

I2C

Digital I/O.

SPI data in.

I2C data I/O.

RC5/SDO

RC5

SDO

16 13

I/O

—

Digital I/O.

SPI data out.

RC6/TX/CK

RC6

17 14

I/O

—

Digital I/O.

EUSART asynchronous transmit.

EUSART synchronous clock (see related RX/DT).

RC7/RX/DT

RC7

18 15

I/O

Digital I/O.

EUSART asynchronous receive.

EUSART synchronous data (see related TX/CK).

RE3 — — — — See MCLR/VPP/RE3 pin.

VSS 8, 19 5, 16 P — Ground reference for logic and I/O pins.

VDD 20 17 P — Positive supply for logic and I/O pins.

TABLE 1-2: PIC18F2221/2321 PINOUT I/O DESCRIPTIONS (CONTINUED)

Pin Name

Pin Number

Type

Buffer

Type Description

SPDIP,

SOIC,

SSOP

QFN

Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output

ST = Schmitt Trigger input with CMOS levels I = Input P = Power

I2C = ST with I2C™ or SMB levels O = Output

Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.

2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.

PIC18F2221/2321/4221/4321 FAMILY

TABLE 1-3: PIC18F4221/4321 PINOUT I/O DESCRIPTIONS

Pin Name

Pin Number Pin

Type

Buffer

Type Description

PDIP QFN TQFP

MCLR/VPP/RE3

MCLR

VPP

RE3

11818

Master Clear (input) or programming voltage (input).

Master Clear (Reset) input. This pin is an active-low

Reset to the device.

Programming voltage input.

Digital input.

OSC1/CLKI/RA7

OSC1

CLKI

RA7

13 32 30

I/O

Analog

TTL

Oscillator crystal or external clock input.

Oscillator crystal input or external clock source input.

ST buffer when configured in RC mode;

analog otherwise.

External clock source input. Always associated with

pin function OSC1. (See related OSC1/CLKI,

OSC2/CLKO pins.)

General purpose I/O pin.

OSC2/CLKO/RA6

OSC2

CLKO

RA6

14 33 31

I/O

—

TTL

Oscillator crystal or clock output.

Oscillator crystal output. Connects to crystal

or resonator in Crystal Oscillator mode.

In RC, EC and INTIO modes, OSC2 pin outputs

CLKO which has one-fourth the frequency of OSC1

and denotes the instruction cycle rate.

General purpose I/O pin.

Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output

ST = Schmitt Trigger input with CMOS levels I = Input P = Power

I2C = ST with I2C™ or SMB levels O = Output

Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.

2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.

PIC18F2221/2321/4221/4321 FAMILY

PORTA is a bidirectional I/O port.

RA0/AN0

RA0

AN0

21919

I/O

TTL

Analog

Digital I/O.

Analog Input 0.

RA1/AN1

RA1

AN1

32020

I/O

TTL

Analog

Digital I/O.

Analog Input 1.

RA2/AN2/VREF-/CVREF

RA2

AN2

VREF-

CVREF

42121

I/O

TTL

Analog

Digital I/O.

Analog Input 2.

A/D reference voltage (low) input.

Comparator reference voltage output.

RA3/AN3/VREF+

RA3

AN3

VREF+

52222

I/O

TTL

Analog

Digital I/O.

Analog Input 3.

A/D reference voltage (high) input.

RA4/T0CKI/C1OUT

RA4

T0CKI

C1OUT

62323

I/O

—

Digital I/O.

Timer0 external clock input.

Comparator 1 output.

RA5/AN4/SS/HLVDIN/

C2OUT

RA5

AN4

HLVDIN

C2OUT

72424

I/O

TTL

Analog

TTL

Analog

—

Digital I/O.

Analog Input 4.

SPI slave select input.

High/Low-Voltage Detect input.

Comparator 2 output.

RA6 See the OSC2/CLKO/RA6 pin.

RA7 See the OSC1/CLKI/RA7 pin.

TABLE 1-3: PIC18F4221/4321 PINOUT I/O DESCRIPTIONS (CONTINUED)

Pin Name

Pin Number Pin

Type

Buffer

Type Description

PDIP QFN TQFP

Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output

ST = Schmitt Trigger input with CMOS levels I = Input P = Power

I2C = ST with I2C™ or SMB levels O = Output

Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.

2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.

PIC18F2221/2321/4221/4321 FAMILY

PORTB is a bidirectional I/O port. PORTB can be

software programmed for internal weak pull-ups on all

inputs.

RB0/INT0/FLT0/AN12

RB0

INT0

FLT0

AN12

33 9 8

I/O

TTL

Analog

Digital I/O.

External Interrupt 0.

PWM Fault input for Enhanced CCP1.

Analog input 12.

RB1/INT1/AN10

RB1

INT1

AN10

34 10 9

I/O

TTL

Analog

Digital I/O.

External Interrupt 1.

Analog Input 10.

RB2/INT2/AN8

RB2

INT2

AN8

35 11 10

I/O

TTL

Analog

Digital I/O.

External Interrupt 2.

Analog Input 8.

RB3/AN9/CCP2

RB3

AN9

CCP2(2)

36 12 11

I/O

TTL

Analog

Digital I/O.

Analog Input 9.

Capture 2 input/Compare 2 output/PWM2 output.

RB4/KBI0/AN11

RB4

KBI0

AN11

37 14 14

I/O

TTL

Analog

Digital I/O.

Interrupt-on-change pin.

Analog input 11.

RB5/KBI1/PGM

RB5

KBI1

PGM

38 15 15

I/O

TTL

Digital I/O.

Interrupt-on-change pin.

Low-Voltage ICSP™ Programming enable pin.

RB6/KBI2/PGC

RB6

KBI2

PGC

39 16 16

I/O

TTL

Digital I/O.

Interrupt-on-change pin.

In-circuit debugger and ICSP programming

clock pin.

RB7/KBI3/PGD

RB7

KBI3

PGD

40 17 17

I/O

TTL

Digital I/O.

Interrupt-on-change pin.

In-circuit debugger and ICSP programming

data pin.

TABLE 1-3: PIC18F4221/4321 PINOUT I/O DESCRIPTIONS (CONTINUED)

Pin Name

Pin Number Pin

Type

Buffer

Type Description

PDIP QFN TQFP

Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output

ST = Schmitt Trigger input with CMOS levels I = Input P = Power

I2C = ST with I2C™ or SMB levels O = Output

Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.

2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.

PIC18F2221/2321/4221/4321 FAMILY

PORTC is a bidirectional I/O port.

RC0/T1OSO/T13CKI

RC0

T1OSO

T13CKI

15 34 32

I/O

—

Digital I/O.

Timer1 oscillator analog output.

Timer1/Timer3 external clock input.

RC1/T1OSI/CCP2

RC1

T1OSI

CCP2(1)

16 35 35

I/O

CMOS

Digital I/O.

Timer1 oscillator analog input.

Capture 2 input/Compare 2 output/PWM2 output.

RC2/CCP1/P1A

RC2

CCP1

P1A

17 36 36

I/O

—

Digital I/O.

Capture 1 input/Compare 1 output/PWM1 output.

Enhanced CCP1 output.

RC3/SCK/SCL

RC3

SCK

SCL

18 37 37

I/O

I2C

Digital I/O.

Synchronous serial clock input/output for

SPI mode.

Synchronous serial clock input/output for I2C™

mode.

RC4/SDI/SDA

RC4

SDI

SDA

23 42 42

I/O

I2C

Digital I/O.

SPI data in.

I2C data I/O.

RC5/SDO

RC5

SDO

24 43 43

I/O

—

Digital I/O.

SPI data out.

RC6/TX/CK

RC6

25 44 44

I/O

—

Digital I/O.

EUSART asynchronous transmit.

EUSART synchronous clock (see related RX/DT).

RC7/RX/DT

RC7

26 1 1

I/O

Digital I/O.

EUSART asynchronous receive.

EUSART synchronous data (see related TX/CK).

TABLE 1-3: PIC18F4221/4321 PINOUT I/O DESCRIPTIONS (CONTINUED)

Pin Name

Pin Number Pin

Type

Buffer

Type Description

PDIP QFN TQFP

Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output

ST = Schmitt Trigger input with CMOS levels I = Input P = Power

I2C = ST with I2C™ or SMB levels O = Output

Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.

2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.

PIC18F2221/2321/4221/4321 FAMILY

PORTD is a bidirectional I/O port or a Parallel Slave

Port (PSP) for interfacing to a microprocessor port.

These pins have TTL input buffers when the PSP

module is enabled.

RD0/PSP0

RD0

PSP0

19 38 38

I/O

TTL

Digital I/O.

Parallel Slave Port data.

RD1/PSP1

RD1

PSP1

20 39 39

I/O

TTL

Digital I/O.

Parallel Slave Port data.

RD2/PSP2

RD2

PSP2

21 40 40

I/O

TTL

Digital I/O.

Parallel Slave Port data.

RD3/PSP3

RD3

PSP3

22 41 41

I/O

TTL

Digital I/O.

Parallel Slave Port data.

RD4/PSP4

RD4

PSP4

27 2 2

I/O

TTL

Digital I/O.

Parallel Slave Port data.

RD5/PSP5/P1B

RD5

PSP5

P1B

28 3 3

I/O

TTL

—

Digital I/O.

Parallel Slave Port data.

Enhanced CCP1 output.

RD6/PSP6/P1C

RD6

PSP6

P1C

29 4 4

I/O

TTL

—

Digital I/O.

Parallel Slave Port data.

Enhanced CCP1 output.

RD7/PSP7/P1D

RD7

PSP7

P1D

30 5 5

I/O

TTL

—

Digital I/O.

Parallel Slave Port data.

Enhanced CCP1 output.

TABLE 1-3: PIC18F4221/4321 PINOUT I/O DESCRIPTIONS (CONTINUED)

Pin Name

Pin Number Pin

Type

Buffer

Type Description

PDIP QFN TQFP

Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output

ST = Schmitt Trigger input with CMOS levels I = Input P = Power

I2C = ST with I2C™ or SMB levels O = Output

Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.

2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.

PIC18F2221/2321/4221/4321 FAMILY

PORTE is a bidirectional I/O port.

RE0/RD/AN5

RE0

AN5

82525

I/O

TTL

Analog

Digital I/O.

Read control for Parallel Slave Port

(see also WR and CS pins).

Analog Input 5.

RE1/WR/AN6

RE1

AN6

92626

I/O

TTL

Analog

Digital I/O.

Write control for Parallel Slave Port

(see CS and RD pins).

Analog Input 6.

RE2/CS/AN7

RE2

AN7

10 27 27

I/O

TTL

Analog

Digital I/O.

Chip Select control for Parallel Slave Port

(see related RD and WR).

Analog Input 7.

RE3 — — — — — See MCLR/VPP/RE3 pin.

VSS 12, 31 6, 30,

6, 29 P — Ground reference for logic and I/O pins.

VDD 11, 32 7, 8,

28, 29

7, 28 P — Positive supply for logic and I/O pins.

NC — 13 12, 13,

33, 34

— — No Connect.

TABLE 1-3: PIC18F4221/4321 PINOUT I/O DESCRIPTIONS (CONTINUED)

Pin Name

Pin Number Pin

Type

Buffer

Type Description

PDIP QFN TQFP

Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output

ST = Schmitt Trigger input with CMOS levels I = Input P = Power

I2C = ST with I2C™ or SMB levels O = Output

Note 1: Default assignment for CCP2 when Configuration bit, CCP2MX, is set.

2: Alternate assignment for CCP2 when Configuration bit, CCP2MX, is cleared.

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

2.0 GUIDELINES FOR GETTING

STARTED WITH PIC18F

MICROCONTROLLERS

2.1 Basic Connection Requirements

Getting started with the PIC18F2221/2321/4221/4321

family family of 8-bit microcontrollers requires attention

to a minimal set of device pin connections before

proceeding with development.

The following pins must always be connected:

•All V

DD and VSS pins

(see Section 2.2 “Power Supply Pins”)

•All AV

DD and AVSS pins, regardless of whether or

not the analog device features are used

(see Section 2.2 “Power Supply Pins”)

•M

CLR pin

(see Section 2.3 “Master Clear (MCLR) Pin”)

These pins must also be connected if they are being

used in the end application:

• PGC/PGD pins used for In-Circuit Serial

Programming™ (ICSP™) and debugging purposes

(see Section 2.4 “ICSP Pins”)

• OSCI and OSCO pins when an external oscillator

source is used

(see Section 2.5 “External Oscillator Pins”)

Additionally, the following pins may be required:

•V

REF+/VREF- pins used when external voltage

reference for analog modules is implemented

The minimum mandatory connections are shown in

Figure 2-1.

FIGURE 2-1: RECOMMENDED

MINIMUM CONNECTIONS

Note: The AVDD and AVSS pins must always be

connected, regardless of whether any of

the analog modules are being used.

PIC18FXXXX

VDD

VSS

VDD

VSS

VDD

AVDD

AVSS

VDD

VSS

VDD

MCLR

C2(1)

C3(1)

C4(1)

C5(1)

C6(1)

Key (all values are recommendations):

C1 through C6: 0.1 μF, 20V ceramic

C7: 10 μF, 16V tantalum or ceramic

R1: 10 kΩ

R2: 100Ω to 470Ω

Note 1: The example shown is for a PIC18F device

with five VDD/VSS and AVDD/AVSS pairs.

Other devices may have more or less pairs;

adjust the number of decoupling capacitors

appropriately.

PIC18F2221/2321/4221/4321 FAMILY

2.2 Power Supply Pins

2.2.1 DECOUPLING CAPACITORS

The use of decoupling capacitors on every pair of

power supply pins, such as VDD, VSS, AVDD and

AVSS, is required.

Consider the following criteria when using decoupling

capacitors:

•Value and type of capacitor: A 0.1 μF (100 nF),

10-20V capacitor is recommended. The capacitor

should be a low-ESR device with a resonance

frequency in the range of 200 MHz and higher.

Ceramic capacitors are recommended.

•Placement on the printed circuit board: The

decoupling capacitors should be placed as close

to the pins as possible. It is recommended to

place the capacitors on the same side of the

board as the device. If space is constricted, the

capacitor can be placed on another layer on the

PCB using a via; however, ensure that the trace

length from the pin to the capacitor is no greater

than 0.25 inch (6 mm).

•Handling high-frequency noise: If the board is

experiencing high-frequency noise (upward of

tens of MHz), add a second ceramic type capaci-

tor in parallel to the above described decoupling

capacitor. The value of the second capacitor can

be in the range of 0.01 μF to 0.001 μF. Place this

second capacitor next to each primary decoupling

capacitor. In high-speed circuit designs, consider

implementing a decade pair of capacitances as

close to the power and ground pins as possible

(e.g., 0.1 μF in parallel with 0.001 μF).

•Maximizing performance: On the board layout

from the power supply circuit, run the power and

return traces to the decoupling capacitors first,

and then to the device pins. This ensures that the

decoupling capacitors are first in the power chain.

Equally important is to keep the trace length

between the capacitor and the power pins to

a minimum, thereby reducing PCB trace

inductance.

2.2.2 TANK CAPACITORS

On boards with power traces running longer than six

inches in length, it is suggested to use a tank capacitor

for integrated circuits including microcontrollers to

supply a local power source. The value of the tank

capacitor should be determined based on the trace

resistance that connects the power supply source to

the device and the maximum current drawn by the

device in the application. In other words, select the tank

capacitor so that it meets the acceptable voltage sag at

the device. Typical values range from 4.7 μF to 47 μF.

2.3 Master Clear (MCLR) Pin

The MCLR pin provides two specific device

functions: device Reset, and device programming

and debugging. If programming and debugging are

not required in the end application, a direct

connection to VDD may be all that is required. The

addition of other components, to help increase the

application’s resistance to spurious Resets from

voltage sags, may be beneficial. A typical

configuration is shown in Figure 2-1. Other circuit

designs may be implemented depending on the

application’s requirements.

During programming and debugging, the resistance

and capacitance that can be added to the pin must

be considered. Device programmers and debuggers

drive the MCLR pin. Consequently, specific voltage

levels (VIH and VIL) and fast signal transitions must

not be adversely affected. Therefore, specific values

of R1 and C1 will need to be adjusted based on the

application and PCB requirements. For example, it is

recommended that the capacitor, C1, be isolated

from the MCLR pin during programming and

debugging operations by using a jumper (Figure 2-2).

The jumper is replaced for normal run-time

operations.

Any components associated with the MCLR pin

should be placed within 0.25 inch (6 mm) of the pin.

FIGURE 2-2: EXAMPLE OF MCLR PIN

CONNECTIONS

Note 1: R1 ≤10 kΩ is recommended. A suggested

starting value is 10 kΩ. Ensure that the

MCLR pin VIH and VIL specifications are met.

2: R2 ≤470Ω will limit any current flowing into

MCLR from the external capacitor, C, in the

event of MCLR pin breakdown, due to

Electrostatic Discharge (ESD) or Electrical

Overstress (EOS). Ensure that the MCLR pin

VIH and VIL specifications are met.

VDD

MCLR

PIC18FXXXX

PIC18F2221/2321/4221/4321 FAMILY

2.4 ICSP Pins

The PGC and PGD pins are used for In-Circuit Serial

Programming (ICSP) and debugging purposes. It is

recommended to keep the trace length between the

ICSP connector and the ICSP pins on the device as

short as possible. If the ICSP connector is expected to

experience an ESD event, a series resistor is recom-

mended, with the value in the range of a few tens of

ohms, not to exceed 100Ω.

Pull-up resistors, series diodes and capacitors on the

PGC and PGD pins are not recommended as they will

interfere with the programmer/debugger com-

munications to the device. If such discrete components

are an application requirement, they should be removed

from the circuit during programming and debugging.

Alternatively, refer to the AC/DC characteristics and

timing requirements information in the respective device

Flash programming specification for information on

capacitive loading limits and pin input voltage high (VIH)

and input low (VIL) requirements.

For device emulation, ensure that the “Communication

Channel Select” (i.e., PGC/PGD pins) programmed

into the device matches the physical connections for

the ICSP to the MPLAB® ICD 2, MPLAB ICD 3 or REAL

ICE™ emulator.

For more information on the ICD 2, ICD 3 and REAL

ICE emulator connection requirements, refer to the

following documents that are available on the

Microchip web site.

•“MPLAB® ICD 2 In-Circuit Debugger User’s

Guide” (DS51331)

•“Using MPLAB® ICD 2” (poster) (DS51265)

•“MPLAB® ICD 2 Design Advisory” (DS51566)

•“Using MPLAB® ICD 3” (poster) (DS51765)

•“MPLAB® ICD 3 Design Advisory” (DS51764)

•“MPLAB® REAL ICE™ In-Circuit Emulator User’s

Guide” (DS51616)

•“Using MPLAB® REAL ICE™ In-Circuit Emulator”

(poster) (DS51749)

2.5 External Oscillator Pins

Many microcontrollers have options for at least two

oscillators: a high-frequency primary oscillator and a

low-frequency secondary oscillator (refer to

Section 3.0 “Oscillator Configurations” for details).

The oscillator circuit should be placed on the same

side of the board as the device. Place the oscillator

circuit close to the respective oscillator pins with no

more than 0.5 inch (12 mm) between the circuit

components and the pins. The load capacitors should

be placed next to the oscillator itself, on the same side

of the board.

Use a grounded copper pour around the oscillator

circuit to isolate it from surrounding circuits. The

grounded copper pour should be routed directly to the

MCU ground. Do not run any signal traces or power

traces inside the ground pour. Also, if using a

two-sided board, avoid any traces on the other side of

the board where the crystal is placed. A suggested

layout is shown in Figure 2-3.

For additional information and design guidance on

oscillator circuits, please refer to these Microchip

Application Notes, available at the corporate web site

(www.microchip.com):

•AN826, “Crystal Oscillator Basics and Crystal

Selection for rfPIC™ and PICmicro® Devices”

• AN849, “Basic PICmicro® Oscillator Design”

• AN943, “Practical PICmicro® Oscillator Analysis

and Design”

• AN949, “Making Your Oscillator Work”

FIGURE 2-3: SUGGESTED PLACEMENT

OF THE OSCILLATOR

CIRCUIT

2.6 Unused I/Os

Unused I/O pins should be configured as outputs and

driven to a logic low state. Alternatively, connect a 1 kΩ

to 10 kΩ resistor to VSS on unused pins and drive the

output to logic low.

Main Oscillator

Guard Ring

Guard Trace

Secondary

Oscillator

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

3.0 OSCILLATOR

CONFIGURATIONS

3.1 Oscillator Types

The PIC18F2221/2321/4221/4321 family of devices

can be operated in ten different oscillator modes. The

user can program the Configuration bits, FOSC<3:0>,

in Configuration Register 1H to select one of these ten

modes:

1. LP Low-Power Crystal

2. XT Crystal/Resonator

3. HS High-Speed Crystal/Resonator

4. HSPLL High-Speed Crystal/Resonator

with PLL enabled

5. RC External Resistor/Capacitor with

FOSC/4 output on RA6

6. RCIO External Resistor/Capacitor with I/O

on RA6

7. INTIO1 Internal Oscillator with FOSC/4 output

on RA6 and I/O on RA7

8. INTIO2 Internal Oscillator with I/O on RA6

and RA7

9. EC External Clock with FOSC/4 output

10. ECIO External Clock with I/O on RA6

3.2 Crystal Oscillator/Ceramic

Resonators

In XT, LP, HS or HSPLL Oscillator modes, a crystal or

ceramic resonator is connected to the OSC1 and

OSC2 pins to establish oscillation. Figure 3-1 shows

the pin connections.

The oscillator design requires the use of a parallel cut

crystal.

FIGURE 3-1: CRYSTAL/CERAMIC

RESONATOR OPERATION

(XT, LP, HS OR HSPLL

CONFIGURATION)

TABLE 3-1: CAPACITOR SELECTION FOR

CERAMIC RESONATORS

Note: Use of a series cut crystal may give a

frequency out of the crystal manufacturer’s

specifications.

Typical Capacitor Values Used:

Mode Freq OSC1 OSC2

XT 3.58 MHz 22 pF 22 pF

Capacitor values are for design guidance only.

Different capacitor values may be required to produce

acceptable oscillator operation. The user should test

the performance of the oscillator over the expected

VDD and temperature range for the application. Refer

to the following application notes for oscillator specific

information:

•AN588, “PIC® Microcontroller Oscillator Design

Guide”

•AN826, “Crystal Oscillator Basics and Crystal

Selection for rfPIC® and PIC® Devices”

•AN849, “Basic PIC® Oscillator Design”

•AN943, “Practical PIC® Oscillator Analysis and

Design”

• AN949, “Making Your Oscillator Work”

See the notes following Table 3-2 for additional

information.

Note: When using resonators with frequencies

above 3.5 MHz, the use of HS mode,

rather than XT mode, is recommended.

HS mode may be used at any VDD for

which the controller is rated. If HS is

selected, it is possible that the gain of the

oscillator will overdrive the resonator.

Therefore, a series resistor may be placed

between the OSC2 pin and the resonator.

As a good starting point, the

recommended value of RS is 330Ω.

Note 1: See Table 3-1 and Table 3-2 for initial values of

C1 and C2.

2: A series resistor (RS) may be required for AT

strip cut crystals.

3: RF varies with the oscillator mode chosen.

C1(1)

C2(1)

XTAL

OSC2

OSC1

RF(3)

Sleep

Logic

PIC18FXXXX

RS(2)

Internal

PIC18F2221/2321/4221/4321 FAMILY

TABLE 3-2: CAPACITOR SELECTION FOR

QUARTZ CRYSTALS

An external clock source may also be connected to the

OSC1 pin in the HS mode, as shown in Figure 3-2.

When operated in this mode, parameters D033 and

D043 apply.

FIGURE 3-2: EXTERNAL CLOCK INPUT

OPERATION (HS OSC

CONFIGURATION)

3.3 External Clock Input

The EC and ECIO Oscillator modes require an external

clock source to be connected to the OSC1 pin. There is

no oscillator start-up time required after a Power-on

Reset or after an exit from Sleep mode.

In the EC Oscillator mode, the oscillator frequency

divided by 4 is available on the OSC2 pin. This signal

may be used for test purposes or to synchronize other

logic. Figure 3-3 shows the pin connections for the EC

Oscillator mode.

FIGURE 3-3: EXTERNAL CLOCK

INPUT OPERATION

(EC CONFIGURATION)

The ECIO Oscillator mode functions like the EC mode,

except that the OSC2 pin becomes an additional

general purpose I/O pin. The I/O pin becomes bit 6 of

PORTA (RA6). Figure 3-4 shows the pin connections

for the ECIO Oscillator mode. When operated in this

mode, parameters D033A and D043A apply.

FIGURE 3-4: EXTERNAL CLOCK

INPUT OPERATION

(ECIO CONFIGURATION)

Osc Type Crystal

Freq

Typical Capacitor Values

Tested:

C1 C2

LP 32 kHz 22 pF 22 pF

XT 1 MHz

4 MHz

22 pF

HS 4 MHz

10 MHz

20 MHz

25 MHz

22 pF

Capacitor values are for design guidance only.

Different capacitor values may be required to produce

acceptable oscillator operation. The user should test

the performance of the oscillator over the expected

VDD and temperature range for the application. Refer

to the following application notes for oscillator specific

information:

•AN588, “PIC® Microcontroller Oscillator Design

Guide”

•AN826, “Crystal Oscillator Basics and Crystal

Selection for rfPIC® and PIC® Devices”

•AN849, “Basic PIC® Oscillator Design”

•AN943, “Practical PIC® Oscillator Analysis and

Design”

• AN949, “Making Your Oscillator Work”

See the notes following this table for additional

information.

Note 1: Higher capacitance increases the stability

of the oscillator but also increases the

start-up time.

2: When operating below 3V VDD, or when

using certain ceramic resonators at any

voltage, it may be necessary to use the

HS mode or switch to a crystal oscillator.

3: Since each resonator/crystal has its own

characteristics, the user should consult

the resonator/crystal manufacturer for

appropriate values of external

components.

4: Rs may be required to avoid overdriving

crystals with low drive level specification.

5: Always verify oscillator performance over

the VDD and temperature range that is

expected for the application.

OSC1

OSC2

Open

Clock from

Ext. System PIC18FXXXX

(HS Mode)

OSC1/CLKI

OSC2/CLKO

FOSC/4

Clock from

Ext. System PIC18FXXXX

OSC1/CLKI

I/O (OSC2)

RA6

Clock from

Ext. System PIC18FXXXX

PIC18F2221/2321/4221/4321 FAMILY

3.4 RC Oscillator

For timing insensitive applications, the RC and RCIO

Oscillator modes offer additional cost savings. The

actual oscillator frequency is a function of several

factors:

• supply voltage

• values of the external resistor (REXT) and

capacitor (CEXT)

• operating temperature

Given the same device, operating voltage, temperature

and component values, there will also be unit-to-unit

frequency variations. These are due to factors such as:

• normal manufacturing variation

• difference in lead frame capacitance between

package types (especially for low CEXT values)

• variations within the tolerance of limits of REXT

and CEXT

In the RC Oscillator mode, the oscillator frequency

divided by 4 is available on the OSC2 pin. This signal

may be used for test purposes or to synchronize other

logic. Figure 3-5 shows how the R/C combination is

connected.

FIGURE 3-5: RC OSCILLATOR MODE

The RCIO Oscillator mode (Figure 3-6) functions like

the RC mode, except that the OSC2 pin becomes an

additional general purpose I/O pin. The I/O pin

becomes bit 6 of PORTA (RA6).

FIGURE 3-6: RCIO OSCILLATOR MODE

3.5 PLL Frequency Multiplier

A Phase Locked Loop (PLL) circuit is provided as an

option for users who wish to use a lower frequency

oscillator circuit or to clock the device up to its highest

rated frequency from a crystal oscillator. This may be

useful for customers who are concerned with EMI due

to high-frequency crystals or users who require higher

clock speeds from an internal oscillator.

3.5.1 HSPLL OSCILLATOR MODE

The HSPLL mode makes use of the HS mode oscillator

for frequencies up to 10 MHz. A PLL then multiplies the

oscillator output frequency by 4 to produce an internal

clock frequency up to 40 MHz. The PLLEN bit is not

available when this mode is configured as the primary

clock source.

The PLL is only available to the crystal oscillator when

the FOSC<3:0> Configuration bits are programmed for

HSPLL mode (= 0110).

FIGURE 3-7: HSPLL BLOCK DIAGRAM

3.5.2 PLL AND INTOSC

The PLL is also available to the internal oscillator block

when the internal oscillator block is configured as the

primary clock source. In this configuration, the PLL is

enabled in software and generates a clock output of up

to 32 MHz. The operation of INTOSC with the PLL is

described in Section 3.6.4 “PLL in INTOSC Modes”.

OSC2/CLKO

CEXT

REXT

PIC18FXXXX

OSC1

FOSC/4

Internal

Clock

VDD

VSS

Recommended values: 3 kΩ ≤ REXT ≤ 100 kΩ

20 pF ≤ CEXT ≤ 300 pF

CEXT

REXT

PIC18FXXXX

OSC1 Internal

Clock

VDD

VSS

Recommended values: 3 kΩ ≤ REXT ≤ 100 kΩ

20 pF ≤ CEXT ≤ 300 pF

I/O (OSC2)

RA6

MUX

VCO

Loop

Filter

Crystal

Osc

OSC2

OSC1

PLL Enable

FIN

FOUT

SYSCLK

Phase

Comparator

HS Oscillator Enable

÷4

(from Configuration Register 1H)

HS Mode

PIC18F2221/2321/4221/4321 FAMILY

3.6 Internal Oscillator Block

The PIC18F2221/2321/4221/4321 family of devices

includes an internal oscillator block which generates

two different clock signals; either can be used as the

microcontroller’s clock source. This may eliminate the

need for external oscillator circuits on the OSC1 and/or

OSC2 pins.

The main output (INTOSC) is an 8 MHz clock source,

which can be used to directly drive the device clock. It

also drives a postscaler, which can provide a range of

clock frequencies from 31 kHz to 4 MHz. The INTOSC

output is enabled when a clock frequency from 125 kHz

to 8 MHz is selected. The INTOSC output can also be

enabled when 31 kHz is selected, depending on the

INTSRC bit (OSCTUNE<7>).

The other clock source is the internal RC oscillator

(INTRC), which provides a nominal 31 kHz output.

INTRC is enabled if it is selected as the device clock

source; it is also enabled automatically when any of the

following are enabled:

• Power-up Timer

• Fail-Safe Clock Monitor

• Watchdog Timer

• Two-Speed Start-up

These features are discussed in greater detail in

Section 24.0 “Special Features of the CPU”.

The clock source frequency (INTOSC direct, INTRC

direct or INTOSC postscaler) is selected by configuring

the IRCF bits of the OSCCON register (page 37).

3.6.1 INTIO MODES

Using the internal oscillator as the clock source elimi-

nates the need for up to two external oscillator pins,

which can then be used for digital I/O. Two distinct

configurations are available:

• In INTIO1 mode, the OSC2 pin outputs FOSC/4,

while OSC1 functions as RA7 (see Figure 3-8) for

digital input and output.

• In INTIO2 mode, OSC1 functions as RA7 and

OSC2 functions as RA6 (see Figure 3-9), both for

digital input and output.

FIGURE 3-8: INTIO1 OSCILLATOR MODE

FIGURE 3-9: INTIO2 OSCILLATOR MODE

3.6.2 INTOSC OUTPUT FREQUENCY

The internal oscillator block is calibrated at the factory

to produce an INTOSC output frequency of 8 MHz.

The INTRC oscillator operates independently of the

INTOSC source. Any changes in INTOSC across

voltage and temperature are not necessarily reflected

by changes in INTRC or vice versa.

3.6.3 OSCTUNE REGISTER

The INTOSC output has been calibrated at the

factory but can be adjusted in the user’s application.

This is done by writing to TUN<4:0>

(OSCTUNE<4:0>) in the OSCTUNE register

(Register 3-1).

When the OSCTUNE register is modified, the INTOSC

frequency will begin shifting to the new frequency.

Code execution continues during this shift. There is no

indication that the shift has occurred. The INTRC is not

affected by OSCTUNE.

The OSCTUNE register also implements the INTSRC

(OSCTUNE<7>) and PLLEN (OSCTUNE<6>) bits,

which control certain features of the internal oscillator

block. The INTSRC bit allows users to select which

internal oscillator provides the clock source when the

31 kHz frequency option is selected. This is covered in

greater detail in Section 3.7.1 “Oscillator Control

The PLLEN bit controls the operation of the Phase

Locked Loop (PLL) in Internal Oscillator modes (see

Figure 3-10).

FIGURE 3-10: INTOSC AND PLL BLOCK

DIAGRAM

PIC18FXXXX

OSC2

FOSC/4

I/O (OSC1)

RA7

PIC18FXXXX

I/O (OSC2)

RA6

I/O (OSC1)

RA7

MUX

VCO

Loop

Filter

OSC2

PLLEN

FIN

FOUT

SYSCLK

Phase

Comparator

8 or 4 MHz

÷4

(OSCTUNE<6>)

MUX

RA6

CLKO

INTOSC

PIC18F2221/2321/4221/4321 FAMILY

3.6.4 PLL IN INTOSC MODES

The 4x Phase Locked Loop (PLL) can be used with the

internal oscillator block to produce faster device clock

speeds than are normally possible with the internal

oscillator sources. When enabled, the PLL produces a

clock speed of 16 MHz or 32 MHz.

Unlike HSPLL mode, the PLL is controlled through

software. The control bit, PLLEN (OSCTUNE<6>), is

used to enable or disable its operation. If PLL is

enabled and a Two-Speed Start-up from wake is

performed, execution is delayed until the PLL starts.

The PLL is available when the device is configured to

use the internal oscillator block as its primary clock

source (FOSC<3:0> = 1001 or 1000). Additionally, the

PLL will only function when the selected output fre-

quency is either 4 MHz or 8 MHz (OSCCON<6:4> = 111

or 110). If both of these conditions are not met, the PLL

is disabled and the PLLEN bit remains clear (writes are

ignored).

3.6.5 INTOSC FREQUENCY DRIFT

The factory calibrates the internal oscillator block

output (INTOSC) for 8 MHz. However, this frequency

may drift as VDD or temperature changes and can

affect the controller operation in a variety of ways. It is

possible to adjust the INTOSC frequency by modifying

the value in the OSCTUNE register. This has no effect

on the INTRC clock source frequency.

Tuning the INTOSC source requires knowing when to

make the adjustment, in which direction it should be

made and in some cases, how large a change is

needed. Three compensation techniques are discussed

in Section 3.6.5.1 “Compensating with the

EUSART”, Section 3.6.5.2 “Compensating with the

Timers” and Section 3.6.5.3 “Compensating with the

CCP Module in Capture Mode” but other techniques

may be used.

R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

INTSRC PLLEN(1) — TUN4 TUN3 TUN2 TUN1 TUN0

bit 7 bit 0

bit 7 INTSRC: Internal Oscillator Low-Frequency Source Select bit

1 = 31.25 kHz device clock derived from 8 MHz INTOSC source (divide-by-256 enabled)

0 = 31 kHz device clock derived directly from INTRC internal oscillator

bit 6 PLLEN: Frequency Multiplier PLL for INTOSC Enable bit(1)

1 = PLL enabled for INTOSC (4 MHz and 8 MHz only)

0 = PLL disabled

Note 1: Available only in certain oscillator configurations; otherwise, this bit is unavailable

and reads as ‘0’. See Section 3.6.4 “PLL in INTOSC Modes” for details.

bit 5 Unimplemented: Read as ‘0’

bit 4-0 TUN<4:0>: Frequency Tuning bits

01111 = Maximum frequency

• •

00001

00000 = Center frequency. Oscillator module is running at the calibrated frequency.

11111

• •

10000 = Minimum frequency

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

3.6.5.1 Compensating with the EUSART

An adjustment may be required when the EUSART

begins to generate framing errors or receives data with

errors while in Asynchronous mode. Framing errors

indicate that the device clock frequency is too high. To

adjust for this, decrement the value in OSCTUNE to

reduce the clock frequency. On the other hand, errors

in data may suggest that the clock speed is too low. To

compensate, increment OSCTUNE to increase the

clock frequency.

3.6.5.2 Compensating with the Timers

This technique compares device clock speed to some

reference clock. Two timers may be used; one timer is

clocked by the peripheral clock, while the other is

clocked by a fixed reference source, such as the

Timer1 oscillator.

Both timers are cleared, but the timer clocked by the

reference generates interrupts. When an interrupt

occurs, the internally clocked timer is read and both

timers are cleared. If the internally clocked timer value

is much greater than expected, then the internal

oscillator block is running too fast. To adjust for this,

decrement the OSCTUNE register.

3.6.5.3 Compensating with the CCP Module

in Capture Mode

A CCP module can use free running Timer1 (or

Timer3), clocked by the internal oscillator block and an

external event with a known period (i.e., AC power

frequency). The time of the first event is captured in the

CCPRxH:CCPRxL registers and is recorded for use

later. When the second event causes a capture, the

time of the first event is subtracted from the time of the

second event. Since the period of the external event is

known, the time difference between events can be

calculated.

If the measured time is much greater than the

calculated time, the internal oscillator block is running

too fast. To compensate, decrement the OSCTUNE

calculated time, the internal oscillator block is running

too slow. To compensate, increment the OSCTUNE

PIC18F2221/2321/4221/4321 FAMILY

3.7 Clock Sources and Oscillator

Switching

The PIC18F2221/2321/4221/4321 family of devices

includes a feature that allows the device clock source

to be switched from the main oscillator to an alternate

clock source. These devices also offer two alternate

clock sources. When an alternate clock source is

enabled, the various power-managed operating modes

are available.

Essentially, there are three clock sources for these

devices:

• Primary oscillators

• Secondary oscillators

• Internal oscillator block

The primary oscillators include the External Crystal

and Resonator modes, the External RC modes, the

External Clock modes and the internal oscillator block.

The particular mode is defined by the FOSC<3:0> Con-

figuration bits. The details of these modes are covered

earlier in this chapter.

The secondary oscillators are those external sources

not connected to the OSC1 or OSC2 pins. These

sources may continue to operate even after the

controller is placed in a power-managed mode.

The PIC18F2221/2321/4221/4321 family of devices

offers the Timer1 oscillator as a secondary oscillator.

This oscillator, in all power-managed modes, is often

the time base for functions such as a Real-Time Clock.

Most often, a 32.768 kHz watch crystal is connected

between the RC0/T1OSO/T13CKI and RC1/T1OSI

pins. Like the LP mode oscillator circuit, loading

capacitors are also connected from each pin to ground.

The Timer1 oscillator is discussed in greater detail in

Section 13.3 “Timer1 Oscillator”.

In addition to being a primary clock source, the internal

oscillator block is available as a power-managed

mode clock source. The INTRC source is also used as

the clock source for several special features, such as

the WDT and Fail-Safe Clock Monitor.

The clock sources for the PIC18F2221/2321/4221/4321

family of devices are shown in Figure 3-11. See

Section 24.0 “Special Features of the CPU” for

Configuration register details.

FIGURE 3-11: PIC18F2221/2321/4221/4321 FAMILY CLOCK DIAGRAM

4 x PLL

FOSC<3:0>

Secondary Oscillator

T1OSCEN

Enable

Oscillator

T1OSO

T1OSI

Clock Source Option

for Other Modules

OSC1

OSC2

Sleep HSPLL, INTOSC/PLL

LP, XT, HS, RC, EC

T1OSC

CPU

Peripherals

IDLEN

Postscaler

MUX

8 MHz

4 MHz

2 MHz

1 MHz

500 kHz

125 kHz

250 kHz

OSCCON<6:4>

111

110

101

100

011

010

001

000

31 kHz

INTRC

Source

Internal

Oscillator

Block

WDT, PWRT, FSCM

8 MHz

Internal Oscillator

(INTOSC)

OSCCON<6:4>

Clock

Control

OSCCON<1:0>

Source

8 MHz

31 kHz (INTRC)

OSCTUNE<6>

OSCTUNE<7>

and Two-Speed Start-up

Primary Oscillator

PIC18F2221/2321/4221/4321 FAMILY

3.7.1 OSCILLATOR CONTROL REGISTER

The OSCCON register (Register 3-2) controls several

aspects of the device clock’s operation, both in full

power operation and in power-managed modes.

The System Clock Select bits, SCS<1:0>, select the

clock source. The available clock sources are the

primary clock (defined by the FOSC<3:0> Configura-

tion bits), the secondary clock (Timer1 oscillator) and

the internal oscillator block. The clock source changes

immediately after either of the SCS<1:0> bits are

changed, following a brief clock transition interval. The

SCS bits are reset on all forms of Reset.

The Internal Oscillator Frequency Select bits

(IRCF<2:0>) select the frequency output of the internal

oscillator block to drive the device clock. The choices

are the INTRC source (31 kHz), the INTOSC source

(8 MHz) or one of the frequencies derived from the

INTOSC postscaler (31.25 kHz to 4 MHz). If the

internal oscillator block is supplying the device clock,

changing the states of these bits will have an immedi-

ate change on the internal oscillator’s output. On

device Resets, the default output frequency of the

internal oscillator block is set at 1 MHz.

When a nominal output frequency of 31 kHz is selected

(IRCF<2:0> = 000), users may choose which internal

oscillator acts as the source. This is done with the

INTSRC bit in the OSCTUNE register (OSCTUNE<7>).

Setting this bit selects INTOSC as a 31.25 kHz clock

source derived from the INTOSC postscaler. Clearing

INTSRC selects INTRC (nominally 31 kHz) as the

clock source and disables the INTOSC to reduce

current consumption.

This option allows users to select the tunable and more

precise INTOSC as a clock source, while maintaining

power savings with a very low clock speed. Addition-

ally, the INTOSC source will already be stable should a

switch to a higher frequency be needed quickly.

Regardless of the setting of INTSRC, INTRC always

remains the clock source for features such as the

Watchdog Timer and the Fail-Safe Clock Monitor.

The OSTS, IOFS and T1RUN bits indicate which clock

source is currently providing the device clock. The

OSTS bit indicates that the Oscillator Start-up Timer

and PLL Start-up Timer (if enabled) have timed out and

the primary clock is providing the device clock in

primary clock modes. The IOFS bit indicates when the

internal oscillator block has stabilized and is providing

the device clock in RC Clock modes. The T1RUN bit

(T1CON<6>) indicates when the Timer1 oscillator is

providing the device clock in secondary clock modes.

In power-managed modes, only one of these three bits

will be set at any time. If none of these bits are set, the

INTRC is providing the clock or the internal oscillator

block has just started and is not yet stable.

The IDLEN bit controls whether the device goes into

Sleep mode or one of the Idle modes when the SLEEP

instruction is executed.

The use of the flag and control bits in the OSCCON

“Power-Managed Modes”.

3.7.2 OSCILLATOR TRANSITIONS

The PIC18F2221/2321/4221/4321 family of devices con-

tains circuitry to prevent clock “glitches” when switching

between clock sources. A short pause in the device clock

occurs during the clock switch. The length of this pause

is the sum of two cycles of the old clock source and three

to four cycles of the new clock source. This formula

assumes that the new clock source is stable.

Clock transitions are discussed in greater detail in

Section 4.1.2 “Entering Power-Managed Modes”.

Note 1: The Timer1 oscillator must be enabled to

select the secondary clock source. The

Timer1 oscillator is enabled by setting the

T1OSCEN bit in the Timer1 Control regis-

ter (T1CON<3>). If the Timer1 oscillator

is not enabled, then any attempt to select

a secondary clock source will be ignored.

2: It is recommended that the Timer1

oscillator be operating and stable before

selecting the secondary clock source or a

very long delay may occur while the

Timer1 oscillator starts.

PIC18F2221/2321/4221/4321 FAMILY

R/W-0 R/W-1 R/W-0 R/W-0 R(1) R-0 R/W-0 R/W-0

IDLEN IRCF2 IRCF1 IRCF0 OSTS IOFS SCS1 SCS0

bit 7 bit 0

bit 7 IDLEN: Idle Enable bit

1 = Device enters an Idle mode when a SLEEP instruction is executed

0 = Device enters Sleep mode when a SLEEP instruction is executed

bit 6-4 IRCF<2:0>: Internal Oscillator Frequency Select bits

111 = 8 MHz (INTOSC drives clock directly)

110 = 4MHz

101 = 2MHz

100 = 1MHz

(3)

011 = 500 kHz

010 = 250 kHz

001 = 125 kHz

000 = 31 kHz (from either INTOSC/256 or INTRC directly)(2)

bit 3 OSTS: Oscillator Start-up Time-out Status bit(1)

1 = Oscillator Start-up Timer (OST) time-out has expired; primary oscillator is running

0 = Oscillator Start-up Timer (OST) time-out is running; primary oscillator is not ready

bit 2 IOFS: INTOSC Frequency Stable bit

1 = INTOSC frequency is stable

0 = INTOSC frequency is not stable

bit 1-0 SCS<1:0>: System Clock Select bits

1x = Internal oscillator block

01 = Secondary (Timer1) oscillator

00 = Primary oscillator

Note 1: Reset state depends on state of the IESO Configuration bit.

2: Source selected by the INTSRC bit (OSCTUNE<7>), see text.

3: Default output frequency of INTOSC on Reset.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

3.8 Effects of Power-Managed Modes

on the Various Clock Sources

When PRI_IDLE mode is selected, the designated pri-

mary oscillator continues to run without interruption.

For all other power-managed modes, the oscillator

using the OSC1 pin is disabled. The OSC1 pin (and

OSC2 pin in Crystal Oscillator modes) will stop

oscillating.

In secondary clock modes (SEC_RUN and

SEC_IDLE), the Timer1 oscillator is operating and

providing the device clock. The Timer1 oscillator may

also run in all power-managed modes if required to

clock Timer1 or Timer3.

In internal oscillator modes (RC_RUN and RC_IDLE),

the internal oscillator block provides the device clock

source. The 31 kHz INTRC output can be used directly

to provide the clock and may be enabled to support

various special features, regardless of the power-

managed mode (see Section 24.2 “Watchdog Timer

(WDT)”, Section 24.3 “Two-Speed Start-up” and

Section 24.4 “Fail-Safe Clock Monitor” for more

information). The INTOSC output at 8 MHz may be

used directly to clock the device or may be divided

down by the postscaler. The INTOSC output is disabled

if the clock is provided directly from the INTRC output.

The INTOSC output is also enabled for Two-Speed

Start-up at 1 MHz after a Reset.

If the Sleep mode is selected, all clock sources are

stopped. Since all the transistor switching currents

have been stopped, Sleep mode achieves the lowest

current consumption of the device (only leakage

currents).

Enabling any on-chip feature that will operate during

Sleep will increase the current consumed during Sleep.

The INTRC is required to support WDT operation. The

Timer1 oscillator may be operating to support a Real-

Time Clock. Other features may be operating that do

not require a device clock source (i.e., MSSP slave,

PSP, INTx pins and others). Peripherals that may add

significant current consumption are listed in

Section 27.2 “DC Characteristics”.

3.9 Power-up Delays

Power-up delays are controlled by two or three timers,

so that no external Reset circuitry is required for most

applications. The delays ensure that the device is kept

in Reset until the device power supply is stable under

normal circumstances and the primary clock is operat-

ing and stable. For additional information on power-up

delays, see Section 5.5 “Device Reset Timers”.

The first timer is the Power-up Timer (PWRT) which

provides a fixed delay on power-up (parameter 33,

Table 27-10). It is enabled by clearing (= 0) the

PWRTEN Configuration bit (CONFIG2L<0>).

3.9.1 DELAYS FOR POWER-UP AND

RETURN TO PRIMARY CLOCK

The second timer is the Oscillator Start-up Timer

(OST), intended to delay execution until the crystal

oscillator is stable (LP, XT and HS modes). The OST

does this by counting 1024 oscillator cycles before

allowing the oscillator to clock the device.

When the HSPLL Oscillator mode is selected, a third

timer delays execution for an additional 2 ms following

the HS mode OST delay, so the PLL can lock to the

incoming clock frequency. At the end of these delays,

the OSTS bit (OSCCON<3>) is set.

There is a delay of interval T

CSD (parameter 38,

Table 27-10), once execution is allowed to start, when

the controller becomes ready to execute instructions.

This delay runs concurrently with any other delays.

This may be the only delay that occurs when any of the

EC, RC or INTIO modes are used as the primary clock

source.

TABLE 3-3: OSC1 AND OSC2 PIN STATES IN SLEEP MODE

OSC Mode OSC1 Pin OSC2 Pin

RC, INTIO1 Floating, external resistor pulls high At logic low (clock/4 output)

RCIO Floating, external resistor pulls high Configured as PORTA, bit 6

INTIO2 Configured as PORTA, bit 7 Configured as PORTA, bit 6

ECIO Floating, driven by external clock Configured as PORTA, bit 6

EC Floating, driven by external clock At logic low (clock/4 output)

LP, XT and HS Feedback inverter disabled at quiescent

voltage level

Feedback inverter disabled at quiescent

voltage level

Note: See Table 5-2 in Section 5.0 “Reset” for time-outs due to Sleep and MCLR Reset.

PIC18F2221/2321/4221/4321 FAMILY

4.0 POWER-MANAGED MODES

PIC18F2221/2321/4221/4321 family devices offer a

total of seven operating modes for more efficient

power-management. These modes provide a variety of

options for selective power conservation in applications

where resources may be limited (i.e., battery-powered

devices).

There are three categories of power-managed modes:

• Run modes

• Idle modes

• Sleep mode

These categories define which portions of the device

are clocked and sometimes, what speed. The Run and

Idle modes may use any of the three available clock

sources (primary, secondary or internal oscillator

block); the Sleep mode does not use a clock source.

The power-managed modes include several power-

saving features offered on previous PIC® devices. One

is the clock switching feature, offered in other PIC18

devices, allowing the controller to use the Timer1 oscil-

lator in place of the primary oscillator. Also included is

the Sleep mode, offered by all PIC devices, where all

device clocks are stopped.

4.1 Selecting Power-Managed Modes

Selecting a power-managed mode requires two

decisions: if the CPU is to be clocked or not and the

selection of a clock source. The IDLEN bit

(OSCCON<7>) controls CPU clocking, while the

SCS<1:0 bits (OSCCON<1:0>) select the clock source.

The individual modes, bit settings, clock sources and

affected modules are summarized in Table 4-1.

4.1.1 CLOCK SOURCES

The SCS<1:0 bits allow the selection of one of three

clock sources for power-managed modes. They are:

• the primary clock, as defined by the FOSC<3:0>

Configuration bits

• the secondary clock (the Timer1 oscillator)

• the internal oscillator block (for RC modes)

4.1.2 ENTERING POWER-MANAGED

MODES

Switching from one power-managed mode to another

begins by loading the OSCCON register. The

SCS1:SCS0 bits select the clock source and determine

which Run or Idle mode is to be used. Changing these

bits causes an immediate switch to the new clock

source, assuming that it is running. The switch may

also be subject to clock transition delays. These are

discussed in Section 4.1.3 “Clock Transitions and

Status Indicators” and subsequent sections.

Entry to the power-managed Idle or Sleep modes is

triggered by the execution of a SLEEP instruction. The

actual mode that results depends on the status of the

IDLEN bit.

Depending on the current mode and the mode being

switched to, a change to a power-managed mode does

not always require setting all of these bits. Many

transitions may be done by changing the oscillator select

bits, or changing the IDLEN bit, prior to issuing a SLEEP

instruction. If the IDLEN bit is already configured

correctly, it may only be necessary to perform a SLEEP

instruction to switch to the desired mode.

TABLE 4-1: POWER-MANAGED MODES

Mode

OSCCON Bits Module Clocking

Available Clock and Oscillator Source

IDLEN<7>(1) SCS<1:0> CPU Peripherals

Sleep 0N/A Off Off None – All clocks are disabled

PRI_RUN N/A 00 Clocked Clocked Primary – LP, XT, HS, HSPLL, RC, EC and

Internal Oscillator Block.(2)

This is the normal full power execution mode.

SEC_RUN N/A 01 Clocked Clocked Secondary – Timer1 Oscillator

RC_RUN N/A 1x Clocked Clocked Internal Oscillator Block(2)

PRI_IDLE 100Off Clocked Primary – LP, XT, HS, HSPLL, RC, EC

SEC_IDLE 101Off Clocked Secondary – Timer1 Oscillator

RC_IDLE 11xOff Clocked Internal Oscillator Block(2)

Note 1: IDLEN reflects its value when the SLEEP instruction is executed.

2: Includes INTOSC and INTOSC postscaler, as well as the INTRC source.

PIC18F2221/2321/4221/4321 FAMILY

4.1.3 CLOCK TRANSITIONS AND STATUS

INDICATORS

The length of the transition between clock sources is

the sum of two cycles of the old clock source and three

to four cycles of the new clock source. This formula

assumes that the new clock source is stable.

Three bits indicate the current clock source and its

status. They are:

• OSTS (OSCCON<3>)

• IOFS (OSCCON<2>)

• T1RUN (T1CON<6>)

In general, only one of these bits will be set while in a

given power-managed mode. When the OSTS bit is

set, the primary clock is providing the device clock.

When the IOFS bit is set, the INTOSC output is

providing a stable 8 MHz clock source to a divider that

actually drives the device clock. When the T1RUN bit is

set, the Timer1 oscillator is providing the clock. If none

of these bits are set, then either the INTRC clock

source is clocking the device, or the INTOSC source is

not yet stable.

If the internal oscillator block is configured as the primary

clock source by the FOSC<3:0> Configuration bits, then

both the OSTS and IOFS bits may be set when in

PRI_RUN or PRI_IDLE modes. This indicates that the

primary clock (INTOSC) is generating a stable 8 MHz

output. Switching the clock source to the Timer1

oscillator would clear the OSTS bit.

4.1.4 MULTIPLE SLEEP COMMANDS

The power-managed mode that is invoked with the

SLEEP instruction is determined by the setting of the

IDLEN bit at the time the instruction is executed. If

another SLEEP instruction is executed, the device will

enter the power-managed mode specified by IDLEN at

that time. If IDLEN has changed, the device will enter

the new power-managed mode specified by the new

setting.

4.2 Run Modes

In the Run modes, clocks to both the core and

peripherals are active. The difference between these

modes is the clock source.

4.2.1 PRI_RUN MODE

The PRI_RUN mode is the normal, full power execution

mode of the microcontroller. This is also the default

mode upon a device Reset unless Two-Speed Start-up

is enabled (see Section 24.3 “Two-Speed Start-up”

or Section 24.4 “Fail-Safe Clock Monitor” for

details). In this mode, the OSTS bit is set. The IOFS bit

may be set if the internal oscillator block is the primary

clock source (see Section 3.7.1 “Oscillator Control

4.2.2 SEC_RUN MODE

The SEC_RUN mode is the compatible mode to the

“clock switching” feature offered in other PIC18

devices. In this mode, the CPU and peripherals are

clocked from the Timer1 oscillator. This gives users the

option of lower power consumption while still using a

high-accuracy clock source.

SEC_RUN mode is entered by setting the SCS<1:0>

bits to ‘01’. The device clock source is switched to the

Timer1 oscillator (see Figure 4-1), the primary oscillator

is shut down, the T1RUN bit (T1CON<6>) is set and the

OSTS bit is cleared.

On transitions from SEC_RUN mode to PRI_RUN, the

peripherals and CPU continue to be clocked from the

Timer1 oscillator while the primary clock is started.

When the primary clock becomes ready, a clock switch

back to the primary clock occurs (see Figure 4-2).

When the clock switch is complete, the T1RUN bit is

cleared, the OSTS bit is set and the primary clock is

providing the clock. The IDLEN and SCS bits are not

affected by the wake-up; the Timer1 oscillator

continues to run.

Note 1: Caution should be used when modifying a

single IRCF bit. If VDD is less than 3V, it is

possible to select a higher clock speed

than is supported by the low VDD.

Improper device operation may result if

the VDD/FOSC specifications are violated.

2: Executing a SLEEP instruction does not

necessarily place the device into Sleep

mode. It acts as the trigger to place the

controller into either the Sleep mode or

one of the Idle modes, depending on the

setting of the IDLEN bit.

Note: The Timer1 oscillator should already be

running prior to entering SEC_RUN mode.

If the T1OSCEN bit is not set when the

SCS<1:0> bits are set to ‘01’, entry to

SEC_RUN mode will not occur. If the

Timer1 oscillator is enabled, but not yet

running, device clocks will be delayed until

the oscillator has started. In such situa-

tions, initial oscillator operation is far from

stable and unpredictable operation may

result.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 4-1: TRANSITION TIMING FOR ENTRY TO SEC_RUN MODE

FIGURE 4-2: TRANSITION TIMING FROM SEC_RUN MODE TO PRI_RUN MODE (HSPLL)

4.2.3 RC_RUN MODE

In RC_RUN mode, the CPU and peripherals are

clocked from the internal oscillator block using the

INTOSC multiplexer. In this mode, the primary clock is

shut down. When using the INTRC source, this mode

provides the best power conservation of all the Run

modes, while still executing code. It works well for user

applications which are not highly timing sensitive or do

not require high-speed clocks at all times.

If the primary clock source is the internal oscillator block

(either INTRC or INTOSC), there are no distinguishable

differences between PRI_RUN and RC_RUN modes

during execution. However, a clock switch delay will

occur during entry to and exit from RC_RUN mode.

Therefore, if the primary clock source is the internal

oscillator block, the use of RC_RUN mode is not

recommended.

This mode is entered by setting the SCS1 bit to ‘1’.

Although it is ignored, it is recommended that the SCS0

bit also be cleared; this is to maintain software compat-

ibility with future devices. When the clock source is

switched to the INTOSC multiplexer (see Figure 4-3),

the primary oscillator is shut down and the OSTS bit is

cleared. The IRCF bits may be modified at any time to

immediately change the clock speed.

Q4Q3Q2

OSC1

Peripheral

Program

T1OSI

Counter

Clock

CPU

Clock

PC + 2PC

123

n-1

Clock Transition(1)

Q4Q3Q2 Q1 Q3Q2

PC + 4

Note 1: Clock transition typically occurs within 2-4 TOSC.

Q1 Q3 Q4

OSC1

Peripheral

Program PC

T1OSI

PLL Clock

PC + 4

Output

Q3 Q4 Q1

CPU Clock

PC + 2

Clock

Counter

Q2 Q2 Q3

Note 1: TOST = 1024 TOSC; TPLL = 2 ms (approx). These intervals are not shown to scale.

2: Clock transition typically occurs within 2-4 TOSC.

SCS<1:0> bits Changed

TPLL(1)

12 n-1n

Clock

OSTS bit Set

Transition(2)

TOST(1)

Note: Caution should be used when modifying a

single IRCF bit. If VDD is less than 3V, it is

possible to select a higher clock speed

than is supported by the low VDD.

Improper device operation may result if

the VDD/FOSC specifications are violated.

PIC18F2221/2321/4221/4321 FAMILY

If the IRCF bits and the INTSRC bit are all clear, the

INTOSC output is not enabled and the IOFS bit will

remain clear; there will be no indication of the current

clock source. The INTRC source is providing the

device clocks.

If the IRCF bits are changed from all clear (thus,

enabling the INTOSC output) or if INTSRC is set, the

IOFS bit becomes set after the INTOSC output

becomes stable. Clocks to the device continue while

the INTOSC source stabilizes after an interval of

TIOBST (parameter 39, Table 27-10).

If the IRCF bits were previously at a non-zero value, or

if INTSRC was set before setting SCS1 and the

INTOSC source was already stable, the IOFS bit will

remain set.

On transitions from RC_RUN mode to PRI_RUN mode,

the device continues to be clocked from the INTOSC

multiplexer while the primary clock is started. When the

primary clock becomes ready, a clock switch to the

primary clock occurs (see Figure 4-4). When the clock

switch is complete, the IOFS bit is cleared, the OSTS

bit is set and the primary clock is providing the device

clock. The IDLEN and SCS bits are not affected by the

switch. The INTRC source will continue to run if either

the WDT or the Fail-Safe Clock Monitor is enabled.

FIGURE 4-3: TRANSITION TIMING TO RC_RUN MODE

FIGURE 4-4: TRANSITION TIMING FROM RC_RUN MODE TO PRI_RUN MODE

Q4Q3Q2

OSC1

Peripheral

Program

INTRC

Counter

Clock

CPU

Clock

PC + 2PC

123 n-1n

Clock Transition(1)

Q4Q3Q2 Q1 Q3Q2

PC + 4

Note 1: Clock transition typically occurs within 2-4 TOSC.

Q1 Q3 Q4

OSC1

Peripheral

Program PC

INTOSC

PLL Clock

PC + 4

Output

Q3 Q4 Q1

CPU Clock

PC + 2

Clock

Counter

Q2 Q2 Q3

Note 1: TOST = 1024 TOSC; TPLL = 2 ms (approx). These intervals are not shown to scale.

2: Clock transition typically occurs within 2-4 TOSC.

SCS<1:0> bits Changed

TPLL(1)

12 n-1n

Clock

OSTS bit Set

Transition(2)

Multiplexer

TOST(1)

PIC18F2221/2321/4221/4321 FAMILY

4.3 Sleep Mode

The power-managed Sleep mode in the PIC18F2221/

2321/4221/4321 family devices is identical to the leg-

acy Sleep mode offered in all other PIC devices. It is

entered by clearing the IDLEN bit (the default state on

device Reset) and executing the SLEEP instruction.

This shuts down the selected oscillator (Figure 4-5). All

clock source status bits are cleared.

Entering the Sleep mode from any other mode does not

require a clock switch. This is because no clocks are

needed once the controller has entered Sleep. If the

WDT is selected, the INTRC source will continue to

operate. If the Timer1 oscillator is enabled, it will also

continue to run.

When a wake event occurs in Sleep mode (by interrupt,

Reset or WDT time-out), the device will not be clocked

until the clock source selected by the SCS<1:0> bits

becomes ready (see Figure 4-6), or it will be clocked

from the internal oscillator block if either the Two-Speed

Start-up or the Fail-Safe Clock Monitor are enabled

(see Section 24.0 “Special Features of the CPU”). In

either case, the OSTS bit is set when the primary clock

is providing the device clocks. The IDLEN and SCS bits

are not affected by the wake-up.

4.4 Idle Modes

The Idle modes allow the controller’s CPU to be

selectively shut down while the peripherals continue to

operate. Selecting a particular Idle mode allows users

to further manage power consumption.

If the IDLEN bit is set to a ‘1’ when a SLEEP instruction is

executed, the peripherals will be clocked from the clock

source selected using the SCS<1:0> bits; however, the

CPU will not be clocked. The clock source status bits are

not affected. Setting IDLEN and executing a SLEEP

instruction provides a quick method of switching from a

given Run mode to its corresponding Idle mode.

If the WDT is selected, the INTRC source will continue

to operate. If the Timer1 oscillator is enabled, it will also

continue to run.

Since the CPU is not executing instructions, the only

exits from any of the Idle modes are by interrupt, WDT

time-out or a Reset. When a wake event occurs, CPU

execution is delayed by an interval of TCSD

(parameter 38, Table 27-10) while it becomes ready to

execute code. When the CPU begins executing code,

it resumes with the same clock source for the current

Idle mode. For example, when waking from RC_IDLE

mode, the internal oscillator block will clock the CPU

and peripherals (in other words, RC_RUN mode). The

IDLEN and SCS bits are not affected by the wake-up.

While in any Idle mode or the Sleep mode, a WDT

time-out will result in a WDT wake-up to the Run mode

currently specified by the SCS<1:0> bits.

FIGURE 4-5: TRANSITION TIMING FOR ENTRY TO SLEEP MODE

FIGURE 4-6: TRANSITION TIMING FOR WAKE FROM SLEEP (HSPLL)

Q4Q3Q2

OSC1

Peripheral

Sleep

Program

Q1Q1

Counter

Clock

CPU

Clock

PC + 2PC

Q3 Q4 Q1 Q2

OSC1

Peripheral

Program PC

PLL Clock

Q3 Q4

Output

CPU Clock

Q1 Q2 Q3 Q4 Q1 Q2

Clock

Counter PC + 6

PC + 4

Q1 Q2 Q3 Q4

Wake Event

Note1: TOST = 1024 TOSC; TPLL = 2 ms (approx). These intervals are not shown to scale.

TOST(1) TPLL(1)

OSTS bit Set

PC + 2

PIC18F2221/2321/4221/4321 FAMILY

4.4.1 PRI_IDLE MODE

This mode is unique among the three low-power Idle

modes, in that it does not disable the primary device

clock. For timing sensitive applications, this allows for

the fastest resumption of device operation with its more

accurate primary clock source, since the clock source

does not have to “warm-up” or transition from another

oscillator.

PRI_IDLE mode is entered from PRI_RUN mode by

setting the IDLEN bit and executing a SLEEP instruc-

tion. If the device is in another Run mode, set IDLEN

first, then clear the SCS bits and execute SLEEP.

Although the CPU is disabled, the peripherals continue

to be clocked from the primary clock source specified

by the FOSC<3:0> Configuration bits. The OSTS bit

remains set (see Figure 4-7).

When a wake event occurs, the CPU is clocked from the

primary clock source. A delay of interval TCSD (parame-

ter 38, Table 27-10) is required between the wake event

and when code execution starts. This is required to

allow the CPU to become ready to execute instructions.

After the wake-up, the OSTS bit remains set. The

IDLEN and SCS bits are not affected by the wake-up

(see Figure 4-8).

4.4.2 SEC_IDLE MODE

In SEC_IDLE mode, the CPU is disabled but the

peripherals continue to be clocked from the Timer1

oscillator. This mode is entered from SEC_RUN by

setting the IDLEN bit and executing a SLEEP

instruction. If the device is in another Run mode, set the

IDLEN bit first, then set the SCS<1:0> bits to ‘01’ and

execute SLEEP. When the clock source is switched to

the Timer1 oscillator, the primary oscillator is shut down,

the OSTS bit is cleared and the T1RUN bit is set.

When a wake event occurs, the peripherals continue to

be clocked from the Timer1 oscillator. After an interval

of TCSD following the wake event, the CPU begins exe-

cuting code being clocked by the Timer1 oscillator. The

IDLEN and SCS bits are not affected by the wake-up;

the Timer1 oscillator continues to run (see Figure 4-8).

FIGURE 4-7: TRANSITION TIMING FOR ENTRY TO IDLE MODE

FIGURE 4-8: TRANSITION TIMING FOR WAKE FROM IDLE TO RUN MODE

Note: The Timer1 oscillator should already be

running prior to entering SEC_IDLE mode.

If the T1OSCEN bit is not set when writing

the SCS<1:0> bits, entry to SEC_IDLE

mode will not occur. If the Timer1 oscillator

is enabled but not yet running, peripheral

clocks will be delayed until the oscillator

has started. In such situations, initial oscil-

lator operation is far from stable and

unpredictable operation may result.

Peripheral

Program PC PC + 2

OSC1

Q3 Q4 Q1

CPU Clock

Clock

Counter

OSC1

Peripheral

Program PC

CPU Clock

Q1 Q3 Q4

Clock

Counter

Wake Event

TCSD

PIC18F2221/2321/4221/4321 FAMILY

4.4.3 RC_IDLE MODE

In RC_IDLE mode, the CPU is disabled but the periph-

erals continue to be clocked from the internal oscillator

block using the INTOSC multiplexer. This mode allows

for controllable power conservation during Idle periods.

From RC_RUN, this mode is entered by setting the

IDLEN bit and executing a SLEEP instruction. If the

device is in another Run mode, first set IDLEN, then set

the SCS1 bit and execute SLEEP. Although its value is

ignored, it is recommended that SCS0 also be cleared;

this is to maintain software compatibility with future

devices. The INTOSC multiplexer may be used to

select a higher clock frequency by modifying the IRCF

bits before executing the SLEEP instruction. When the

clock source is switched to the INTOSC multiplexer, the

primary oscillator is shut down and the OSTS bit is

cleared.

If the IRCF bits are set to any non-zero value, or the

INTSRC bit is set, the INTOSC output is enabled. The

IOFS bit becomes set, after the INTOSC output

becomes stable, after an interval of TIOBST

(parameter 39, Table 27-10). Clocks to the peripherals

continue while the INTOSC source stabilizes. If the

IRCF bits were previously at a non-zero value, or

INTSRC was set before the SLEEP instruction was

executed and the INTOSC source was already stable,

the IOFS bit will remain set. If the IRCF bits and

INTSRC are all clear, the INTOSC output will not be

enabled, the IOFS bit will remain clear and there will be

no indication of the current clock source.

When a wake event occurs, the peripherals continue to

be clocked from the INTOSC multiplexer. After a delay of

CSD following the wake event, the CPU begins execut-

ing code being clocked by the INTOSC multiplexer. The

IDLEN and SCS bits are not affected by the wake-up.

The INTRC source will continue to run if either the WDT

or the Fail-Safe Clock Monitor is enabled.

4.5 Exiting Idle and Sleep Modes

An exit from Sleep mode or any of the Idle modes is

triggered by an interrupt, a Reset or a WDT time-out.

This section discusses the triggers that cause exits

from power-managed modes. The clocking subsystem

actions are discussed in each of the power-managed

modes (see Section 4.2 “Run Modes”, Section 4.3

“Sleep Mode” and Section 4.4 “Idle Modes”).

4.5.1 EXIT BY INTERRUPT

Any of the available interrupt sources can cause the

device to exit from an Idle mode, or the Sleep mode to

a Run mode. To enable this functionality, an interrupt

source must be enabled by setting its enable bit in one

of the INTCON or PIE registers. The exit sequence is

initiated when the corresponding interrupt flag bit is set.

On all exits from Idle or Sleep modes by interrupt, code

execution branches to the interrupt vector if the GIE/

GIEH bit (INTCON<7>) is set. Otherwise, code execution

continues or resumes without branching (see

Section 10.0 “Interrupts”).

A fixed delay of interval TCSD following the wake event

is required when leaving Sleep and Idle modes. This

delay is required for the CPU to prepare for execution.

Instruction execution resumes on the first clock cycle

following this delay.

4.5.2 EXIT BY WDT TIME-OUT

A WDT time-out will cause different actions depending

on which power-managed mode the device is in when

the time-out occurs.

If the device is not executing code (all Idle modes and

Sleep mode), the time-out will result in an exit from the

power-managed mode (see Section 4.2 “Run

Modes” and Section 4.3 “Sleep Mode”). If the device

is executing code (all Run modes), the time-out will

result in a WDT Reset (see Section 24.2 “Watchdog

Timer (WDT)”).

The WDT timer and postscaler are cleared by

executing a SLEEP or CLRWDT instruction, the loss of a

currently selected clock source (if the Fail-Safe Clock

Monitor is enabled) and modifying the IRCF bits in the

OSCCON register if the internal oscillator block is the

device clock source.

4.5.3 EXIT BY RESET

Normally, the device is held in Reset by the Oscillator

Start-up Timer (OST) until the primary clock becomes

ready. At that time, the OSTS bit is set and the device

begins executing code. If the internal oscillator block is

the new clock source, the IOFS bit is set instead.

The exit delay time from Reset to the start of code

execution depends on both the clock sources before

and after the wake-up and the type of oscillator if the

new clock source is the primary clock. Exit delays are

summarized in Table 4-2.

Code execution can begin before the primary clock

becomes ready. If either the Two-Speed Start-up (see

Section 24.3 “Two-Speed Start-up”) or Fail-Safe

Clock Monitor (see Section 24.4 “Fail-Safe Clock

Monitor”) is enabled, the device may begin execution

as soon as the Reset source has cleared. Execution is

clocked by the INTOSC multiplexer driven by the

internal oscillator block. Execution is clocked by the

internal oscillator block until either the primary clock

becomes ready or a power-managed mode is entered

before the primary clock becomes ready; the primary

clock is then shut down.

PIC18F2221/2321/4221/4321 FAMILY

4.5.4 EXIT WITHOUT AN OSCILLATOR

START-UP DELAY

Certain exits from power-managed modes do not

invoke the OST at all. There are two cases:

• PRI_IDLE mode, where the primary clock source

is not stopped; and

• the primary clock source is not any of the LP, XT,

HS or HSPLL modes.

In these instances, the primary clock source either

does not require an oscillator start-up delay since it is

already running (PRI_IDLE), or normally does not

require an oscillator start-up delay (RC, EC and INTIO

Oscillator modes). However, a fixed delay of interval

CSD following the wake event is still required when

leaving Sleep and Idle modes to allow the CPU to

prepare for execution. Instruction execution resumes

on the first clock cycle following this delay.

TABLE 4-2: EXIT DELAY ON WAKE-UP BY RESET FROM SLEEP MODE OR ANY IDLE MODE

(BY CLOCK SOURCES)

Clock Source

before Wake-up

Clock Source

after Wake-up Exit Delay Clock Ready Status

Bit (OSCCON)

Primary Device Clock

(PRI_IDLE mode)

LP, XT, HS

CSD(1) OSTSHSPLL

EC, RC

INTOSC(2) IOFS

T1OSC

LP, XT, HS TOST(3)

OSTSHSPLL TOST + trc(3)

EC, RC TCSD(1)

INTOSC(2) TIOBST(4) IOFS

INTOSC(3)

LP, XT, HS TOST(3)

OSTSHSPLL TOST + trc(3)

EC, RC TCSD(1)

INTOSC(2) None IOFS

None

(Sleep mode)

LP, XT, HS TOST(3)

OSTSHSPLL TOST + trc(3)

EC, RC TCSD(1)

INTOSC(2) TIOBST(4) IOFS

Note 1: TCSD (parameter 38) is a required delay when waking from Sleep and all Idle modes and runs concurrently

with any other required delays (see Section 4.4 “Idle Modes”). On Reset, INTOSC defaults to 1 MHz.

2: Includes both the INTOSC 8 MHz source and postscaler derived frequencies.

3: T

OST is the Oscillator Start-up Timer (parameter 32). trc is the PLL Lock-out Timer (parameter F12); it is

also designated as TPLL.

4: Execution continues during TIOBST (parameter 39), the INTOSC stabilization period.

PIC18F2221/2321/4221/4321 FAMILY

5.0 RESET

The PIC18F2221/2321/4221/4321 family devices

differentiate between various kinds of Reset:

a) Power-on Reset (POR)

b) MCLR Reset during normal operation

c) MCLR Reset during power-managed modes

d) Watchdog Timer (WDT) Reset (during

execution)

e) Programmable Brown-out Reset (BOR)

f) RESET Instruction

g) Stack Full Reset

h) Stack Underflow Reset

This section discusses Resets generated by MCLR,

POR and BOR and covers the operation of the various

start-up timers. Stack Reset events are covered in

Section 6.1.2.4 “Stack Full and Underflow Resets”.

WDT Resets are covered in Section 24.2 “Watchdog

Timer (WDT)”.

A simplified block diagram of the On-Chip Reset Circuit

is shown in Figure 5-1.

5.1 RCON Register

Device Reset events are tracked through the RCON

ter indicate that a specific Reset event has occurred. In

most cases, these bits can only be cleared by the event

and must be set by the application after the event. The

state of these flag bits, taken together, can be read to

indicate the type of Reset that just occurred. This is

described in more detail in Section 5.6 “Reset State

of Registers”.

The RCON register also has control bits for setting

interrupt priority (IPEN) and software control of the

BOR (SBOREN). Interrupt priority is discussed in

Section 10.0 “Interrupts”. BOR is covered in

Section 5.4 “Brown-out Reset (BOR)”.

FIGURE 5-1: SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT

External Reset

MCLR

VDD

OSC1

WDT

Time-out

VDD Rise

Detect

OST/PWRT

INTRC

(1)

POR Pulse

OST

10-bit Ripple Counter

PWRT

11-Bit Ripple Counter

Enable OST(2)

Enable PWRT

Note 1: This is the INTRC source from the internal oscillator block and is separate from the RC oscillator of the CLKI pin.

2: See Table 5-2 for time-out situations.

Brown-out

Reset

BOREN

RESET

Instruction

Stack

Pointer

Stack Full/Underflow Reset

Sleep

( )_IDLE

1024 Cycles

65.5 ms

32 μs

MCLRE

Chip_Reset

PIC18F2221/2321/4221/4321 FAMILY

R/W-0 R/W-1(1) U-0 R/W-1 R-1 R-1 R/W-0(2) R/W-0

IPEN SBOREN —RITO PD POR BOR

bit 7 bit 0

bit 7 IPEN: Interrupt Priority Enable bit

1 = Enable priority levels on interrupts

0 = Disable priority levels on interrupts (PIC16CXXX Compatibility mode)

bit 6 SBOREN: BOR Software Enable bit(1)

If BOREN<1:0> = 01:

1 = BOR is enabled

0 = BOR is disabled

If BOREN<1:0> = 00, 10 or 11:

Bit is disabled and read as ‘0’.

bit 5 Unimplemented: Read as ‘0’

bit 4 RI: RESET Instruction Flag bit

1 = The RESET instruction was not executed (set by firmware only)

0 = The RESET instruction was executed causing a device Reset (must be set in software after

a Brown-out Reset occurs)

bit 3 TO: Watchdog Time-out Flag bit

1 = Set by power-up, CLRWDT instruction or SLEEP instruction

0 = A WDT time-out occurred

bit 2 PD: Power-Down Detection Flag bit

1 = Set by power-up or by the CLRWDT instruction

0 = Set by execution of the SLEEP instruction

bit 1 POR: Power-on Reset Status bit(2)

1 = A Power-on Reset has not occurred (set by firmware only)

0 = A Power-on Reset occurred (must be set in software after a Power-on Reset occurs)

bit 0 BOR: Brown-out Reset Status bit

1 = A Brown-out Reset has not occurred (set by firmware only)

0 = A Brown-out Reset occurred (must be set in software after a Brown-out Reset occurs)

Note 1: If SBOREN is enabled, its Reset state is ‘1’; otherwise, it is ‘0’.

2: The actual Reset value of POR is determined by the type of device Reset. See the

notes following this register and Section 5.6 “Reset State of Registers” for

additional information.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

Note 1: It is recommended that the POR bit be set after a Power-on Reset has been

detected so that subsequent Power-on Resets may be detected.

2: Brown-out Reset is said to have occurred when BOR is ‘0’ and POR is ‘1’ (assuming

that POR was set to ‘1’ by software immediately after Power-on Reset).

PIC18F2221/2321/4221/4321 FAMILY

5.2 Master Clear (MCLR)

The MCLR pin provides a method for triggering an

external Reset of the device. A Reset is generated by

holding the pin low. These devices have a noise filter in

the MCLR Reset path which detects and ignores small

pulses.

The MCLR pin is not driven low by any internal Resets,

including the WDT.

In PIC18F2221/2321/4221/4321 family devices, the

MCLR input can be disabled with the MCLRE Configu-

ration bit. When MCLR is disabled, the pin becomes a

digital input. See Section 11.5 “PORTE, TRISE and

LATE Registers” for more information.

5.3 Power-on Reset (POR)

A Power-on Reset pulse is generated on-chip

whenever VDD rises above a certain threshold. This

allows the device to start in the initialized state when

VDD is adequate for operation.

To take advantage of the POR circuitry, tie the MCLR

pin through a resistor (1 kΩ to 10 kΩ) to VDD. This will

eliminate external RC components usually needed to

create a Power-on Reset delay. A minimum rise rate for

VDD is specified (parameter D004). For a slow rise

time, see Figure 5-2.

When the device starts normal operation (i.e., exits the

Reset condition), device operating parameters

(voltage, frequency, temperature, etc.) must be met to

ensure operation. If these conditions are not met, the

device must be held in Reset until the operating

conditions are met.

Power-on Reset events are captured by the POR bit

(RCON<1>). The state of the bit is set to ‘0’ whenever

a POR occurs; it does not change for any other Reset

event. POR is not reset to ‘1’ by any hardware event.

To capture multiple events, the user manually resets

the bit to ‘1’ in software following any POR.

FIGURE 5-2: EXTERNAL POWER-ON

RESET CIRCUIT (FOR

SLOW VDD POWER-UP)

Note 1: External Power-on Reset circuit is required

only if the VDD power-up slope is too slow.

The diode D helps discharge the capacitor

quickly when VDD powers down.

2: R < 40 kΩ is recommended to make sure that

the voltage drop across R does not violate

the device’s electrical specification.

3: R1 ≥ 1 kΩ will limit any current flowing into

MCLR from external capacitor C, in the event

of MCLR/VPP pin breakdown, due to

Electrostatic Discharge (ESD) or Electrical

Overstress (EOS).

VDD

MCLR

PIC18FXXXX

VDD

PIC18F2221/2321/4221/4321 FAMILY

5.4 Brown-out Reset (BOR)

PIC18F2221/2321/4221/4321 family devices implement

a BOR circuit that provides the user with a number of

configuration and power-saving options. The BOR is

controlled by the BORV<1:0> and BOREN<1:0>

Configuration bits. There are a total of four BOR

configurations which are summarized in Table 5-1.

The BOR threshold is set by the BORV<1:0> bits. If BOR

is enabled (any values of BOREN<1:0>, except ‘00’),

any drop of VDD below VBOR (parameter D005) for

greater than TBOR (parameter 35) will reset the device.

A Reset may or may not occur if VDD falls below VBOR

for less than TBOR. The chip will remain in Brown-out

Reset until VDD rises above VBOR.

If the Power-up Timer is enabled, it will be invoked after

VDD rises above VBOR; it then will keep the chip in

Reset for an additional time delay, TPWRT

(parameter 33). If VDD drops below VBOR while the

Power-up Timer is running, the chip will go back into a

Brown-out Reset and the Power-up Timer will be

initialized. Once VDD rises above VBOR, the Power-up

Timer will execute the additional time delay.

BOR and the Power-on Timer (PWRT) are

independently configured. Enabling BOR Reset does

not automatically enable the PWRT.

5.4.1 SOFTWARE ENABLED BOR

When BOREN<1:0> = 01, the BOR can be enabled or

disabled by the user in software. This is done with the

control bit, SBOREN (RCON<6>). Setting SBOREN

enables the BOR to function as previously described.

Clearing SBOREN disables the BOR entirely. The

SBOREN bit operates only in this mode; otherwise it is

read as ‘0’.

Placing the BOR under software control gives the user

the additional flexibility of tailoring the application to its

environment without having to reprogram the device to

change BOR configuration. It also allows the user to

tailor device power consumption in software by elimi-

nating the incremental current that the BOR consumes.

While the BOR current is typically very small, it may

have some impact in low-power applications.

5.4.2 DETECTING BOR

When Brown-out Reset is enabled, the BOR bit always

resets to ‘0’ on any Brown-out Reset or Power-on

Reset event. This makes it difficult to determine if a

Brown-out Reset event has occurred just by reading

the state of BOR alone. A more reliable method is to

simultaneously check the state of both POR and BOR.

This assumes that the POR bit is reset to ‘1’ in software

immediately after any Power-on Reset event. If BOR is

‘0’ while POR is ‘1’, it can be reliably assumed that a

Brown-out Reset event has occurred.

5.4.3 DISABLING BOR IN SLEEP MODE

When BOREN<1:0> = 10, the BOR remains under

hardware control and operates as previously

described. Whenever the device enters Sleep mode,

however, the BOR is automatically disabled. When the

device returns to any other operating mode, BOR is

automatically re-enabled.

This mode allows for applications to recover from

brown-out situations, while actively executing code,

when the device requires BOR protection the most. At

the same time, it saves additional power in Sleep mode

by eliminating the small incremental BOR current.

TABLE 5-1: BOR CONFIGURATIONS

Note: Even when BOR is under software control,

the Brown-out Reset voltage level is still

set by the BORV<1:0> Configuration bits.

It cannot be changed in software.

BOR Configuration Status of

SBOREN

(RCON<6>)

BOR Operation

BOREN1 BOREN0

00Unavailable BOR disabled; must be enabled by reprogramming the Configuration bits.

01Available BOR enabled in software; operation controlled by SBOREN.

10Unavailable BOR enabled in hardware in Run and Idle modes, disabled during

Sleep mode.

11Unavailable BOR enabled in hardware; must be disabled by reprogramming the

Configuration bits.

PIC18F2221/2321/4221/4321 FAMILY

5.5 Device Reset Timers

PIC18F2221/2321/4221/4321 family devices incorpo-

rate three separate on-chip timers that help regulate the

Power-on Reset process. Their main function is to

ensure that the device clock is stable before code is

executed. These timers are:

• Power-up Timer (PWRT)

• Oscillator Start-up Timer (OST)

• PLL Lock Time-out

5.5.1 POWER-UP TIMER (PWRT)

The Power-up Timer (PWRT) of the PIC18F2221/

2321/4221/4321 family devices is an 11-bit counter

which uses the INTRC source as the clock input.

This yields an approximate time interval of

2048 x 32 μs = 65.6 ms. While the PWRT is counting,

the device is held in Reset.

The power-up time delay depends on the INTRC clock

and will vary from chip to chip due to temperature and

process variation. See DC parameter 33 for details.

The PWRT is enabled by clearing the PWRTEN

Configuration bit.

5.5.2 OSCILLATOR START-UP TIMER

(OST)

The Oscillator Start-up Timer (OST) provides a 1024

oscillator cycle (from OSC1 input) delay after the

PWRT delay is over (parameter 33). This ensures that

the crystal oscillator or resonator has started and

stabilized.

The OST time-out is invoked only for XT, LP, HS and

HSPLL modes and only on Power-on Reset, or on exit

from most power-managed modes.

5.5.3 PLL LOCK TIME-OUT

With the PLL enabled in HSPLL mode, the time-out

sequence following a Power-on Reset is slightly differ-

ent from other oscillator modes. A separate timer is

used to provide a fixed time-out that is sufficient for the

PLL to lock to the main oscillator frequency. This PLL

lock time-out (TPLL) is typically 2 ms and follows the

oscillator start-up time-out.

5.5.4 TIME-OUT SEQUENCE

On power-up, the time-out sequence is as follows:

1. After the POR pulse has cleared, PWRT time-out

is invoked (if enabled).

2. Then, the OST is activated.

The total time-out will vary based on oscillator configu-

ration and the status of the PWRT. Figure 5-3,

Figure 5-4, Figure 5-5, Figure 5-6 and Figure 5-7 all

depict time-out sequences on power-up, with the

Power-up Timer enabled and the device operating in

HS Oscillator mode. Figures 5-3 through 5-6 also

apply to devices operating in XT or LP modes. For

devices in RC mode and with the PWRT disabled, there

will be no time-out at all.

Since the time-outs occur from the POR pulse, if MCLR

is kept low long enough, all time-outs will expire. Bring-

ing MCLR high will begin execution immediately

(Figure 5-5). This is useful for testing purposes or to

synchronize more than one PIC18FXXXX device

operating in parallel.

TABLE 5-2: TIME-OUT IN VARIOUS SITUATIONS

Oscillator

Configuration

Power-up(2) and Brown-out Reset Exit from

Power-Managed Mode

PWRTEN = 0PWRTEN = 1

HSPLL 66 ms(1) + 1024 TOSC + 2 ms(2) 1024 TOSC + 2 ms(2) 1024 TOSC + 2 ms(2)

HS, XT, LP 66 ms(1) + 1024 TOSC 1024 TOSC 1024 TOSC

EC, ECIO 66 ms(1) ——

RC, RCIO 66 ms(1) ——

INTIO1, INTIO2 66 ms(1) ——

Note 1: 66 ms (65.5 ms) is the nominal Power-up Timer (PWRT) delay.

2: 2 ms is the nominal time required for the PLL to lock.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 5-3: TIME-OUT SEQUENCE ON POWER-UP (MCLR TIED TO VDD, VDD RISE < TPWRT)

FIGURE 5-4: TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO VDD): CASE 1

FIGURE 5-5: TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO VDD): CASE 2

TPWRT

TOST

VDD

MCLR

INTERNAL POR

PWRT TIME-OUT

OST TIME-OUT

INTERNAL RESET

TPWRT

TOST

VDD

MCLR

INTERNAL POR

PWRT TIME-OUT

OST TIME-OUT

INTERNAL RESET

VDD

MCLR

INTERNAL POR

PWRT TIME-OUT

OST TIME-OUT

INTERNAL RESET

TPWRT

TOST

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 5-6: SLOW RISE TIME (MCLR TIED TO VDD, VDD RISE > TPWRT)

FIGURE 5-7: TIME-OUT SEQUENCE ON POR w/PLL ENABLED (MCLR TIED TO VDD)

VDD

MCLR

INTERNAL POR

PWRT TIME-OUT

OST TIME-OUT

INTERNAL RESET

TPWRT

TOST

TPWRT

TOST

VDD

MCLR

INTERNAL POR

PWRT TIME-OUT

OST TIME-OUT

INTERNAL RESET

PLL TIME-OUT

TPLL

Note: TOST = 1024 clock cycles.

TPLL ≈ 2 ms max. First three stages of the PWRT timer.

PIC18F2221/2321/4221/4321 FAMILY

5.6 Reset State of Registers

Most registers are unaffected by a Reset. Their status

is unknown on POR and unchanged by all other

Resets. The other registers are forced to a “Reset

state” depending on the type of Reset that occurred.

Most registers are not affected by a WDT wake-up,

since this is viewed as the resumption of normal oper-

ation. Status bits from the RCON register, RI, TO, PD,

POR and BOR, are set or cleared differently in different

Reset situations, as indicated in Table 5-3. These bits

are used in software to determine the nature of the

Reset.

Table 5-4 describes the Reset states for all of the

Special Function Registers. These are categorized by

Power-on and Brown-out Resets, Master Clear and

WDT Resets and WDT wake-ups.

TABLE 5-3: STATUS BITS, THEIR SIGNIFICANCE AND THE INITIALIZATION CONDITION

FOR RCON REGISTER

Condition Program

Counter

RCON Register STKPTR Register

RI TO PD POR BOR STKFUL STKUNF

Power-on Reset 0000h 11100 0 0

RESET Instruction 0000h 0uuuu u u

Brown-out 0000h 111u0 u u

MCLR during power-managed Run modes 0000h u1uuu u u

MCLR during power-managed Idle modes

and Sleep mode

0000h u10uu u u

WDT Time-out during full power or

power-managed Run mode

0000h u0uuu u u

MCLR during full power execution 0000h uuuuu u u

Stack Full Reset (STVREN = 1) 0000h uuuuu 1 u

Stack Underflow Reset (STVREN = 1) 0000h uuuuu u 1

Stack Underflow Error (not an actual Reset,

STVREN = 0)

0000h uuuuu u 1

WDT time-out during power-managed Idle or

Sleep modes

PC + 2 u00uu u u

Interrupt exit from power-managed modes PC + 2(1) uu0uu u u

Legend: u = unchanged

Note 1: When the wake-up is due to an interrupt and the GIEH or GIEL bits are set, the PC is loaded with the

interrupt vector (008h or 0018h).

2: Reset state is ‘1’ for POR and unchanged for all other Resets when software BOR is enabled

(BOREN<1:0> Configuration bits = 01 and SBOREN = 1); otherwise, the Reset state is ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

TABLE 5-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS

Brown-out Reset

MCLR Resets,

WDT Reset,

RESET Instruction,

Stack Resets

Wake-up via WDT

or Interrupt

TOSU 2221 2321 4221 4321 ---0 0000 ---0 0000 ---0 uuuu(3)

TOSH 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu(3)

TOSL 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu(3)

STKPTR 2221 2321 4221 4321 00-0 0000 uu-0 0000 uu-u uuuu(3)

PCLATU 2221 2321 4221 4321 --00 0000 --00 0000 --uu uuuu

PCLATH 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

PCL 2221 2321 4221 4321 0000 0000 0000 0000 PC + 2(2)

TBLPTRU 2221 2321 4221 4321 --00 0000 --00 0000 --uu uuuu

TBLPTRH 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

TBLPTRL 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

TABLAT 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

PRODH 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

PRODL 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

INTCON 2221 2321 4221 4321 0000 000x 0000 000u uuuu uuuu(1)

INTCON2 2221 2321 4221 4321 1111 -1-1 1111 -1-1 uuuu -u-u(1)

INTCON3 2221 2321 4221 4321 11-0 0-00 11-0 0-00 uu-u u-uu(1)

INDF0 2221 2321 4221 4321 N/A N/A N/A

POSTINC0 2221 2321 4221 4321 N/A N/A N/A

POSTDEC0 2221 2321 4221 4321 N/A N/A N/A

PREINC0 2221 2321 4221 4321 N/A N/A N/A

PLUSW0 2221 2321 4221 4321 N/A N/A N/A

FSR0H 2221 2321 4221 4321 ---- 0000 ---- 0000 ---- uuuu

FSR0L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

WREG 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

INDF1 2221 2321 4221 4321 N/A N/A N/A

POSTINC1 2221 2321 4221 4321 N/A N/A N/A

POSTDEC1 2221 2321 4221 4321 N/A N/A N/A

PREINC1 2221 2321 4221 4321 N/A N/A N/A

PLUSW1 2221 2321 4221 4321 N/A N/A N/A

Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition.

Shaded cells indicate conditions do not apply for the designated device.

Note 1: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up).

2: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt

vector (0008h or 0018h).

3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are

updated with the current value of the PC. The STKPTR is modified to point to the next location in the

hardware stack.

4: See Table 5-3 for Reset value for specific condition.

5: Bits 6 and 7 of PORTA, LATA and TRISA are enabled, depending on the oscillator mode selected. When

not enabled as PORTA pins, they are disabled and read ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

FSR1H 2221 2321 4221 4321 ---- 0000 ---- 0000 ---- uuuu

FSR1L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

BSR 2221 2321 4221 4321 ---- 0000 ---- 0000 ---- uuuu

INDF2 2221 2321 4221 4321 N/A N/A N/A

POSTINC2 2221 2321 4221 4321 N/A N/A N/A

POSTDEC2 2221 2321 4221 4321 N/A N/A N/A

PREINC2 2221 2321 4221 4321 N/A N/A N/A

PLUSW2 2221 2321 4221 4321 N/A N/A N/A

FSR2H 2221 2321 4221 4321 ---- 0000 ---- 0000 ---- uuuu

FSR2L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

STATUS 2221 2321 4221 4321 ---x xxxx ---u uuuu ---u uuuu

TMR0H 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

TMR0L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

T0CON 2221 2321 4221 4321 1111 1111 1111 1111 uuuu uuuu

OSCCON 2221 2321 4221 4321 0100 q000 0100 q000 uuuu uuqu

HLVDCON 2221 2321 4221 4321 0-00 0101 0-00 0101 u-uu uuuu

WDTCON 2221 2321 4221 4321 ---- ---0 ---- ---0 ---- ---u

RCON(4) 2221 2321 4221 4321 0q-1 11q0 0q-q qquu uq-u qquu

TMR1H 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

TMR1L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

T1CON 2221 2321 4221 4321 0000 0000 u0uu uuuu uuuu uuuu

TMR2 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

PR2 2221 2321 4221 4321 1111 1111 1111 1111 1111 1111

T2CON 2221 2321 4221 4321 -000 0000 -000 0000 -uuu uuuu

SSPBUF 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

SSPADD 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

SSPSTAT 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

SSPCON1 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

SSPCON2 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

TABLE 5-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED)

Brown-out Reset

MCLR Resets,

WDT Reset,

RESET Instruction,

Stack Resets

Wake-up via WDT

or Interrupt

Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition.

Shaded cells indicate conditions do not apply for the designated device.

Note 1: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up).

2: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt

vector (0008h or 0018h).

3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are

updated with the current value of the PC. The STKPTR is modified to point to the next location in the

hardware stack.

4: See Table 5-3 for Reset value for specific condition.

5: Bits 6 and 7 of PORTA, LATA and TRISA are enabled, depending on the oscillator mode selected. When

not enabled as PORTA pins, they are disabled and read ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

ADRESH 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

ADRESL 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

ADCON0 2221 2321 4221 4321 --00 0000 --00 0000 --uu uuuu

ADCON1 2221 2321 4221 4321 --00 0qqq --00 0qqq --uu uuuu

ADCON2 2221 2321 4221 4321 0-00 0000 0-00 0000 u-uu uuuu

CCPR1H 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

CCPR1L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

CCP1CON 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

2221 2321 4221 4321 --00 0000 --00 0000 --uu uuuu

CCPR2H 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

CCPR2L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

CCP2CON 2221 2321 4221 4321 --00 0000 --00 0000 --uu uuuu

BAUDCON 2221 2321 4221 4321 0100 0-00 0100 0-00 --uu uuuu

ECCP1DEL 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

ECCP1AS 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

2221 2321 4221 4321 0000 00-- 0000 00-- uuuu uu--

CVRCON 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

CMCON 2221 2321 4221 4321 0000 0111 0000 0111 uuuu uuuu

TMR3H 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

TMR3L 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

T3CON 2221 2321 4221 4321 0000 0000 uuuu uuuu uuuu uuuu

SPBRGH 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

SPBRG 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

RCREG 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

TXREG 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

TXSTA 2221 2321 4221 4321 0000 0010 0000 0010 uuuu uuuu

RCSTA 2221 2321 4221 4321 0000 000x 0000 000x uuuu uuuu

EEADR 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

EEDATA 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

EECON2 2221 2321 4221 4321 0000 0000 0000 0000 0000 0000

EECON1 2221 2321 4221 4321 xx-0 x000 uu-0 u000 uu-0 u000

TABLE 5-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED)

Brown-out Reset

MCLR Resets,

WDT Reset,

RESET Instruction,

Stack Resets

Wake-up via WDT

or Interrupt

Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition.

Shaded cells indicate conditions do not apply for the designated device.

Note 1: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up).

2: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt

vector (0008h or 0018h).

3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are

updated with the current value of the PC. The STKPTR is modified to point to the next location in the

hardware stack.

4: See Table 5-3 for Reset value for specific condition.

5: Bits 6 and 7 of PORTA, LATA and TRISA are enabled, depending on the oscillator mode selected. When

not enabled as PORTA pins, they are disabled and read ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

IPR2 2221 2321 4221 4321 11-1 1111 11-1 1111 uu-u uuuu

PIR2 2221 2321 4221 4321 00-0 0000 00-0 0000 uu-u uuuu(1)

PIE2 2221 2321 4221 4321 00-0 0000 00-0 0000 uu-u uuuu

IPR1 2221 2321 4221 4321 1111 1111 1111 1111 uuuu uuuu

2221 2321 4221 4321 -111 1111 -111 1111 -uuu uuuu

PIR1 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu(1)

2221 2321 4221 4321 -000 0000 -000 0000 -uuu uuuu(1)

PIE1 2221 2321 4221 4321 0000 0000 0000 0000 uuuu uuuu

2221 2321 4221 4321 -000 0000 -000 0000 -uuu uuuu

OSCTUNE 2221 2321 4221 4321 00-0 0000 00-0 0000 uu-u uuuu

TRISE 2221 2321 4221 4321 0000 -111 0000 -111 uuuu -uuu

TRISD 2221 2321 4221 4321 1111 1111 1111 1111 uuuu uuuu

TRISC 2221 2321 4221 4321 1111 1111 1111 1111 uuuu uuuu

TRISB 2221 2321 4221 4321 1111 1111 1111 1111 uuuu uuuu

TRISA(5) 2221 2321 4221 4321 1111 1111(5) 1111 1111(5) uuuu uuuu(5)

LATE 2221 2321 4221 4321 ---- -xxx ---- -uuu ---- -uuu

LATD 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

LATC 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

LATB 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

LATA(5) 2221 2321 4221 4321 xxxx xxxx(5) uuuu uuuu(5) uuuu uuuu(5)

PORTE 2221 2321 4221 4321 ---- xxxx ---- uuuu ---- uuuu

2221 2321 4221 4321 ---- x--- ---- u--- ---- u---

PORTD 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

PORTC 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

PORTB 2221 2321 4221 4321 xxxx xxxx uuuu uuuu uuuu uuuu

PORTA(5) 2221 2321 4221 4321 xx0x 0000(5) uu0u 0000(5) uuuu uuuu(5)

TABLE 5-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED)

Brown-out Reset

MCLR Resets,

WDT Reset,

RESET Instruction,

Stack Resets

Wake-up via WDT

or Interrupt

Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition.

Shaded cells indicate conditions do not apply for the designated device.

Note 1: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up).

2: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt

vector (0008h or 0018h).

3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are

updated with the current value of the PC. The STKPTR is modified to point to the next location in the

hardware stack.

4: See Table 5-3 for Reset value for specific condition.

5: Bits 6 and 7 of PORTA, LATA and TRISA are enabled, depending on the oscillator mode selected. When

not enabled as PORTA pins, they are disabled and read ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

6.0 MEMORY ORGANIZATION

There are three types of memory in PIC18 Enhanced

microcontroller devices:

• Program Memory

• Data RAM

• Data EEPROM

As Harvard architecture devices, the data and program

memories use separate busses; this allows for con-

current access of the two memory spaces. The data

EEPROM, for practical purposes, can be regarded as

a peripheral device, since it is addressed and accessed

through a set of control registers.

Additional detailed information on the operation of the

Flash program memory is provided in Section 7.0

“Flash Program Memory”. Data EEPROM is

discussed separately in Section 8.0 “Data EEPROM

Memory”.

6.1 Program Memory Organization

PIC18 microcontrollers implement a 21-bit program

counter, which is capable of addressing a 2-Mbyte

program memory space. Accessing a location between

the upper boundary of the physically implemented

memory and the 2-Mbyte address will return all ‘0’s (a

NOP instruction).

The PIC18F2221 and PIC18F4221 each have 4 Kbytes

of Flash memory and can store up to 2048 single-word

instructions. The PIC18F2321 and PIC18F4321 each

have 8 Kbytes of Flash memory and can store up to

4096 single-word instructions.

PIC18 devices have two interrupt vectors. The Reset

vector address is at 0000h and the interrupt vector

addresses are at 0008h and 0018h.

The program memory maps for PIC18F2221/4221 and

PIC18F2321/4321 devices are shown in Figure 6-1.

FIGURE 6-1: PROGRAM MEMORY MAP AND STACK FOR PIC18F2221/2321/4221/4321 FAMILY

DEVICES

PC<20:0>

Stack Level 1

•

Stack Level 31

Reset Vector

Low-Priority Interrupt Vector

•

CALL,RCALL,RETURN

RETFIE,RETLW

0000h

0018h

On-Chip

Program Memory

High-Priority Interrupt Vector 0008h

User Memory Space

1FFFFFh

1000h

0FFFh

Read ‘0’

200000h

PC<20:0>

Stack Level 1

•

Stack Level 31

Reset Vector

Low-Priority Interrupt Vector

•

CALL,RCALL,RETURN

RETFIE,RETLW

0000h

0018h

2000h

1FFFh

On-Chip

Program Memory

High-Priority Interrupt Vector 0008h

User Memory Space

Read ‘0’

1FFFFFh

200000h

PIC18FX221 PIC18FX321

PIC18F2221/2321/4221/4321 FAMILY

6.1.1 PROGRAM COUNTER

The Program Counter (PC) specifies the address of the

instruction to fetch for execution. The PC is 21 bits wide

and is contained in three separate 8-bit registers. The

low byte, known as the PCL register, is both readable

and writable. The high byte, or PCH register, contains

the PC<15:8> bits; it is not directly readable or writable.

Updates to the PCH register are performed through the

PCLATH register. The upper byte is called PCU. This

directly readable or writable. Updates to the PCU

The contents of PCLATH and PCLATU are transferred

to the program counter by any operation that writes

PCL. Similarly, the upper two bytes of the program

counter are transferred to PCLATH and PCLATU by an

operation that reads PCL. This is useful for computed

offsets to the PC (see Section 6.1.4.1 “Computed

GOTO”).

The PC addresses bytes in the program memory. To

prevent the PC from becoming misaligned with word

instructions, the Least Significant bit of PCL is fixed to

a value of ‘0’. The PC increments by 2 to address

sequential instructions in the program memory.

The CALL, RCALL, GOTO and program branch

instructions write to the program counter directly. For

these instructions, the contents of PCLATH and

PCLATU are not transferred to the program counter.

6.1.2 RETURN ADDRESS STACK

The return address stack allows any combination of up

to 31 program calls and interrupts to occur. The PC is

pushed onto the stack when a CALL or RCALL instruc-

tion is executed or an interrupt is Acknowledged. The

PC value is pulled off the stack on a RETURN, RETLW

or a RETFIE instruction. PCLATU and PCLATH are not

affected by any of the RETURN or CALL instructions.

The stack operates as a 31-word by 21-bit RAM and a

5-bit Stack Pointer, STKPTR. The stack space is not

part of either program or data space. The Stack Pointer

is readable and writable and the address on the top of

the stack is readable and writable through the Top-of-

Stack Special Function Registers. Data can also be

pushed to, or popped from the stack, using these

registers.

A CALL type instruction causes a push onto the stack;

the Stack Pointer is first incremented and the location

pointed to by the Stack Pointer is written with the

contents of the PC (already pointing to the instruction

following the CALL). A RETURN type instruction causes

a pop from the stack; the contents of the location

pointed to by the STKPTR are transferred to the PC

and then the Stack Pointer is decremented.

The Stack Pointer is initialized to ‘00000’ after all

Resets. There is no RAM associated with the location

corresponding to a Stack Pointer value of ‘00000’; this

is only a Reset value. Status bits indicate if the stack is

full or has overflowed or has underflowed.

6.1.2.1 Top-of-Stack Access

Only the top of the return address stack (TOS) is

readable and writable. A set of three registers,

TOSU:TOSH:TOSL, hold the contents of the stack

location pointed to by the STKPTR register (Figure 6-2).

This allows users to implement a software stack if

necessary. After a CALL, RCALL or interrupt, the

software can read the pushed value by reading the

TOSU:TOSH:TOSL registers. These values can be

placed on a user-defined software stack. At return time,

the software can return these values to

TOSU:TOSH:TOSL and do a return.

The user must disable the global interrupt enable bits

while accessing the stack to prevent inadvertent stack

corruption.

FIGURE 6-2: RETURN ADDRESS STACK AND ASSOCIATED REGISTERS

00011

001A34h

11111

11110

11101

00010

00001

00000

00010

Return Address Stack <20:0>

To p - o f - St a c k

000D58h

TOSLTOSHTOSU

34h1Ah00h

STKPTR<4:0>

Top-of-Stack Registers Stack Pointer

PIC18F2221/2321/4221/4321 FAMILY

6.1.2.2 Return Stack Pointer (STKPTR)

The STKPTR register (Register 6-1) contains the Stack

Pointer value, the STKFUL (Stack Full) status bit and

the STKUNF (Stack Underflow) status bits. The value

of the Stack Pointer can be 0 through 31. The Stack

Pointer increments before values are pushed onto the

stack and decrements after values are popped off the

stack. On Reset, the Stack Pointer value will be zero.

The user may read and write the Stack Pointer value.

This feature can be used by a Real-Time Operating

System (RTOS) for return stack maintenance.

After the PC is pushed onto the stack 31 times (without

popping any values off the stack), the STKFUL bit is

set. The STKFUL bit is cleared by software or by a

POR.

The action that takes place when the stack becomes

full depends on the state of the STVREN (Stack

Overflow Reset Enable) Configuration bit. (Refer to

Section 24.1 “Configuration Bits” for a description of

the device Configuration bits.) If STVREN is set

(default), the 31st push will push the (PC + 2) value

onto the stack, set the STKFUL bit and reset the

device. The STKFUL bit will remain set and the Stack

Pointer will be set to zero.

If STVREN is cleared, the STKFUL bit will be set on the

31st push and the Stack Pointer will increment to 31.

Any additional pushes will not overwrite the 31st push

and STKPTR will remain at 31.

When the stack has been popped enough times to

unload the stack, the next pop will return a value of zero

to the PC and sets the STKUNF bit, while the Stack

Pointer remains at zero. The STKUNF bit will remain

set until cleared by software or until a POR occurs.

6.1.2.3 PUSH and POP Instructions

Since the Top-of-Stack is readable and writable, the

ability to push values onto the stack and pull values off

the stack without disturbing normal program execution

is a desirable feature. The PIC18 instruction set

includes two instructions, PUSH and POP, that permit

the TOS to be manipulated under software control.

TOSU, TOSH and TOSL can be modified to place data

or a return address on the stack.

The PUSH instruction places the current PC value onto

the stack. This increments the Stack Pointer and loads

the current PC value onto the stack.

The POP instruction discards the current TOS by decre-

menting the Stack Pointer. The previous value pushed

onto the stack then becomes the TOS value.

Note: Returning a value of zero to the PC on an

underflow has the effect of vectoring the

program to the Reset vector, where the

stack conditions can be verified and

appropriate actions can be taken. This is

not the same as a Reset, as the contents

of the SFRs are not affected.

R/C-0 R/C-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

STKFUL(1) STKUNF(1) — SP4 SP3 SP2 SP1 SP0

bit 7 bit 0

bit 7 STKFUL: Stack Full Flag bit(1)

1 = Stack became full or overflowed

0 = Stack has not become full or overflowed

bit 6 STKUNF: Stack Underflow Flag bit(1)

1 = Stack underflow occurred

0 = Stack underflow did not occur

bit 5 Unimplemented: Read as ‘0’

bit 4-0 SP<4:0>: Stack Pointer Location bits

Note 1: Bit 7 and bit 6 are cleared by user software or by a POR.

Legend:

R = Readable bit W = Writable bit U = Unimplemented C = Clearable only bit

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

6.1.2.4 Stack Full and Underflow Resets

Device Resets on stack overflow and stack underflow

conditions are enabled by setting the STVREN bit in

Configuration Register 4L. When STVREN is set, a full

or underflow will set the appropriate STKFUL or

STKUNF bit and then cause a device Reset. When

STVREN is cleared, a full or underflow condition will set

the appropriate STKFUL or STKUNF bit but not cause

a device Reset. The STKFUL or STKUNF bits are

cleared by the user software or a Power-on Reset.

6.1.3 FAST REGISTER STACK

A Fast Register Stack is provided for the STATUS,

WREG and BSR registers, to provide a “fast return”

option for interrupts. The stack for each register is only

one level deep and is neither readable nor writable. It is

loaded with the current value of the corresponding

interrupt sources will push values into the stack regis-

ters. The values in the registers are then loaded back

into their associated registers if the RETFIE, FAST

instruction is used to return from the interrupt.

If both low and high-priority interrupts are enabled, the

stack registers cannot be used reliably to return from

low-priority interrupts. If a high-priority interrupt occurs

while servicing a low-priority interrupt, the Stack regis-

ter values stored by the low-priority interrupt will be

overwritten. In these cases, users must save the key

registers in software during a low-priority interrupt.

If interrupt priority is not used, all interrupts may use the

Fast Register Stack for returns from interrupt. If no

interrupts are used, the Fast Register Stack can be

used to restore the STATUS, WREG and BSR registers

at the end of a subroutine call. To use the Fast Register

Stack for a subroutine call, a CALL label,FAST

instruction must be executed to save the STATUS,

WREG and BSR registers to the Fast Register Stack. A

RETURN, FAST instruction is then executed to restore

these registers from the Fast Register Stack.

Example 6-1 shows a source code example that uses

the Fast Register Stack during a subroutine call and

return.

EXAMPLE 6-1: FAST REGISTER STACK

CODE EXAMPLE

6.1.4 LOOK-UP TABLES IN PROGRAM

MEMORY

There may be programming situations that require the

creation of data structures, or look-up tables, in

program memory. For PIC18 devices, look-up tables

can be implemented in two ways:

• Computed GOTO

• Table Reads

6.1.4.1 Computed GOTO

A computed GOTO is accomplished by adding an offset

to the program counter. An example is shown in

Example 6-2.

A look-up table can be formed with an ADDWF PCL

instruction and a group of RETLW nn instructions. The

W register is loaded with an offset into the table before

executing a call to that table. The first instruction of the

called routine is the ADDWF PCL instruction. The next

instruction executed will be one of the RETLW nn

instructions that returns the value ‘nn’ to the calling

function.

The offset value (in WREG) specifies the number of

bytes that the program counter should advance and

should be multiples of 2 (LSb = 0).

In this method, only one data byte may be stored in

each instruction location and room on the return

address stack is required.

EXAMPLE 6-2: COMPUTED GOTO USING

AN OFFSET VALUE

6.1.4.2 Table Reads and Table Writes

A better method of storing data in program memory

allows two bytes of data to be stored in each instruction

location.

Look-up table data may be stored two bytes per

program word by using table reads and writes. The

Table Pointer (TBLPTR) register specifies the byte

address and the Table Latch (TABLAT) register

contains the data that is read from or written to program

memory. Data is transferred to or from program

memory one byte at a time.

Table read and table write operations are discussed

further in Section 7.1 “Table Reads and Table

Writes”.

CALL SUB1, FAST ;STATUS, WREG, BSR

;SAVED IN FAST REGISTER

;STACK

•

SUB1 •

•

RETURN, FAST ;RESTORE VALUES SAVED

;IN FAST REGISTER STACK

MOVF OFFSET, W

CALL TABLE

ORG nn00h

TABLE ADDWF PCL

RETLW nnh

PIC18F2221/2321/4221/4321 FAMILY

6.2 PIC18 Instruction Cycle

6.2.1 CLOCKING SCHEME

The microcontroller clock input, whether from an

internal or external source, is internally divided by four

to generate four non-overlapping quadrature clocks

(Q1, Q2, Q3 and Q4). Internally, the program counter is

incremented on every Q1; the instruction is fetched

from the program memory and latched into the

Instruction Register (IR) during Q4. The instruction is

decoded and executed during the following Q1 through

Q4. The clocks and instruction execution flow are

shown in Figure 6-3.

6.2.2 INSTRUCTION FLOW/PIPELINING

An “Instruction Cycle” consists of four Q cycles: Q1

through Q4. The instruction fetch and execute are

pipelined in such a manner that a fetch takes one

instruction cycle, while the decode and execute take

another instruction cycle. However, due to the pipe-

lining, each instruction effectively executes in one

cycle. If an instruction causes the program counter to

change (e.g., GOTO), then two cycles are required to

complete the instruction (Example 6-3).

A fetch cycle begins with the Program Counter (PC)

incrementing in Q1.

In the execution cycle, the fetched instruction is latched

into the Instruction Register (IR) in cycle Q1. This

instruction is then decoded and executed during the

Q2, Q3 and Q4 cycles. Data memory is read during Q2

(operand read) and written during Q4 (destination

write).

FIGURE 6-3: CLOCK/INSTRUCTION CYCLE

EXAMPLE 6-3: INSTRUCTION PIPELINE FLOW

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

OSC1

OSC2/CLKO

(RC mode)

PC PC + 2 PC + 4

Fetch INST (PC)

Execute INST (PC – 2)

Fetch INST (PC + 2)

Execute INST (PC)

Fetch INST (PC + 4)

Execute INST (PC + 2)

Internal

Phase

Clock

All instructions are single cycle, except for any program branches. These take two cycles since the fetch instruction

is “flushed” from the pipeline while the new instruction is being fetched and then executed.

TCY0TCY1TCY2TCY3TCY4TCY5

1. MOVLW 55h Fetch 1 Execute 1

2. MOVWF PORTB Fetch 2 Execute 2

3. BRA SUB_1 Fetch 3 Execute 3

4. BSF PORTA, BIT3 (Forced NOP) Fetch 4 Flush (NOP)

5. Instruction @ address SUB_1 Fetch SUB_1 Execute SUB_1

PIC18F2221/2321/4221/4321 FAMILY

6.2.3 INSTRUCTIONS IN PROGRAM

MEMORY

The program memory is addressed in bytes. Instruc-

tions are stored as two bytes or four bytes in program

memory. The Least Significant Byte of an instruction

word is always stored in a program memory location

with an even address (LSb = 0). To maintain alignment

with instruction boundaries, the PC increments in steps

of 2 and the LSb will always read ‘0’ (see Section 6.1.1

“Program Counter”).

Figure 6-4 shows an example of how instruction words

are stored in the program memory.

The CALL and GOTO instructions have the absolute

program memory address embedded into the instruc-

tion. Since instructions are always stored on word

boundaries, the data contained in the instruction is a

word address. The word address is written to PC<20:1>,

which accesses the desired byte address in program

memory. Instruction #2 in Figure 6-4 shows how the

instruction GOTO 0006h is encoded in the program

memory. Program branch instructions, which encode a

relative address offset, operate in the same manner. The

offset value stored in a branch instruction represents the

number of single-word instructions that the PC will be

offset by. Section 24.0 “Instruction Set Summary”

provides further details of the instruction set.

FIGURE 6-4: INSTRUCTIONS IN PROGRAM MEMORY

6.2.4 TWO-WORD INSTRUCTIONS

The standard PIC18 instruction set has four two-word

instructions: CALL, MOVFF, GOTO and LSFR. In all

cases, the second word of the instructions always has

‘1111’ as its four Most Significant bits; the other 12 bits

are literal data, usually a data memory address.

The use of ‘1111’ in the 4 MSbs of an instruction spec-

ifies a special form of NOP. If the instruction is executed

in proper sequence – immediately after the first word –

the data in the second word is accessed and used by

the instruction sequence. If the first word is skipped for

some reason and the second word is executed by itself,

a NOP is executed instead. This is necessary for cases

when the two-word instruction is preceded by a condi-

tional instruction that changes the PC. Example 6-4

shows how this works.

EXAMPLE 6-4: TWO-WORD INSTRUCTIONS

Word Address

LSB = 1LSB = 0↓

Program Memory

Byte Locations →

000000h

000002h

000004h

000006h

Instruction 1: MOVLW 055h 0Fh 55h 000008h

Instruction 2: GOTO 0006h EFh 03h 00000Ah

F0h 00h 00000Ch

Instruction 3: MOVFF 123h, 456h C1h 23h 00000Eh

F4h 56h 000010h

000012h

000014h

Note: See Section 6.6 “PIC18 Instruction

Execution and the Extended Instruc-

tion Set” for information on two-word

instructions in the extended instruction set.

CASE 1:

Object Code Source Code

0110 0110 0000 0000 TSTFSZ REG1 ; is RAM location 0?

1100 0001 0010 0011 MOVFF REG1, REG2 ; No, skip this word

1111 0100 0101 0110 ; Execute this word as a NOP

0010 0100 0000 0000 ADDWF REG3 ; continue code

CASE 2:

Object Code Source Code

0110 0110 0000 0000 TSTFSZ REG1 ; is RAM location 0?

1100 0001 0010 0011 MOVFF REG1, REG2 ; Yes, execute this word

1111 0100 0101 0110 ; 2nd word of instruction

0010 0100 0000 0000 ADDWF REG3 ; continue code

PIC18F2221/2321/4221/4321 FAMILY

6.3 Data Memory Organization

The data memory in PIC18 devices is implemented as

static RAM. Each register in the data memory has a

12-bit address, allowing up to 4096 bytes of data

memory. The memory space is divided into as many as

16 banks that contain 256 bytes each; PIC18F2221/

2321/4221/4321 family devices implement 2 banks.

Figure 6-5 shows the data memory organization for the

PIC18F2221/2321/4221/4321 family devices.

The data memory contains Special Function Registers

(SFRs) and General Purpose Registers (GPRs). The

SFRs are used for control and status of the controller

and peripheral functions, while GPRs are used for data

storage and scratchpad operations in the user’s

application. Any read of an unimplemented location will

read as ‘0’s.

The instruction set and architecture allow operations

across all banks. The entire data memory may be

accessed by Direct, Indirect or Indexed Addressing

modes. Addressing modes are discussed later in this

subsection.

To ensure that commonly used registers (SFRs and

select GPRs) can be accessed in a single cycle, PIC18

devices implement an Access Bank. This is a 256-byte

memory space that provides fast access to SFRs and

the lower portion of GPR Bank 0 without using the

BSR. Section 6.3.2 “Access Bank” provides a

detailed description of the Access RAM.

6.3.1 BANK SELECT REGISTER (BSR)

Large areas of data memory require an efficient

addressing scheme to make rapid access to any

address possible. Ideally, this means that an entire

address does not need to be provided for each read or

write operation. For PIC18 devices, this is accomplished

with a RAM banking scheme. This divides the memory

space into 16 contiguous banks of 256 bytes. Depend-

ing on the instruction, each location can be addressed

directly by its full 12-bit address, or an 8-bit low-order

address and a 4-bit Bank Pointer.

Most instructions in the PIC18 instruction set make use

of the Bank Pointer, known as the Bank Select Register

(BSR). This SFR holds the four Most Significant bits of

a location’s address; the instruction itself includes the

8 Least Significant bits. Only the four lower bits of the

BSR are implemented (BSR3:BSR0). The upper four

bits are unused; they will always read ‘0’ and cannot be

written to. The BSR can be loaded directly by using the

MOVLB instruction.

The value of the BSR indicates the bank in data

memory; the 8 bits in the instruction show the location

in the bank and can be thought of as an offset from the

bank’s lower boundary. The relationship between the

BSR’s value and the bank division in data memory is

shown in Figure 6-6.

Since up to 16 registers may share the same low-order

address, the user must always be careful to ensure that

the proper bank is selected before performing a data

read or write. For example, writing what should be

program data to an 8-bit address of F9h, while the BSR

is 0Fh, will end up resetting the program counter.

While any bank can be selected, only those banks that

are actually implemented can be read or written to.

Writes to unimplemented banks are ignored, while

reads from unimplemented banks will return ‘0’s. Even

so, the STATUS register will still be affected as if the

operation was successful. The data memory map in

Figure 6-5 indicates which banks are implemented.

In the core PIC18 instruction set, only the MOVFF

instruction fully specifies the 12-bit address of the

source and target registers. This instruction ignores the

BSR completely when it executes. All other instructions

include only the low-order address as an operand and

must use either the BSR or the Access Bank to locate

their target registers.

Note: The operation of some aspects of data

memory are changed when the PIC18

extended instruction set is enabled. See

Section 6.5 “Data Memory and the

Extended Instruction Set” for more

information.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 6-5: DATA MEMORY MAP FOR PIC18F2221/2321/4221/4321 FAMILY DEVICES

Bank 0

Bank 14

Bank 15

Data Memory Map

BSR<3:0>

= 0000

= 1111

080h

07Fh

F80h

FFFh

00h

7Fh

80h

FFh

Access Bank

When a = 0,

The BSR is ignored and the

Access Bank is used.

The first 128 bytes are

General Purpose RAM

(from Bank 0).

The second 128 bytes are

Special Function Registers

(from Bank 15).

When a = 1,

The BSR specifies the Bank

used by the instruction.

F7Fh

F00h

EFFh

0FFh

000h

Access RAM

FFh

00h

FFh

00h

GPR

SFR

Unused

Access RAM High

Access RAM Low

Bank 2

to Unused

Read ‘00h’

= 1110

= 0010

(SFRs)

Bank 1

= 0001 100h

1FFh

GPR

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 6-6: USE OF THE BANK SELECT REGISTER (DIRECT ADDRESSING)

6.3.2 ACCESS BANK

While the use of the BSR with an embedded 8-bit

address allows users to address the entire range of

data memory, it also means that the user must always

ensure that the correct bank is selected. Otherwise,

data may be read from or written to the wrong location.

This can be disastrous if a GPR is the intended target

of an operation, but an SFR is written to instead.

Verifying and/or changing the BSR for each read or

write to data memory can become very inefficient.

To streamline access for the most commonly used data

memory locations, the data memory is configured with

an Access Bank, which allows users to access a

mapped block of memory without specifying a BSR.

The Access Bank consists of the first 128 bytes of

memory (00h-7Fh) in Bank 0 and the last 128 bytes of

memory (80h-FFh) in Block 15. The lower half is known

as the “Access RAM” and is composed of GPRs. This

upper half is also where the device’s SFRs are

mapped. These two areas are mapped contiguously in

the Access Bank and can be addressed in a linear

fashion by an 8-bit address (Figure 6-5).

The Access Bank is used by core PIC18 instructions

that include the Access RAM bit (the ‘a’ parameter in

the instruction). When ‘a’ is equal to ‘1’, the instruction

uses the BSR and the 8-bit address included in the

opcode for the data memory address. When ‘a’ is ‘0’,

however, the instruction is forced to use the Access

Bank address map; the current value of the BSR is

ignored entirely.

Using this “forced” addressing allows the instruction to

operate on a data address in a single cycle, without

updating the BSR first. For 8-bit addresses of 80h and

above, this means that users can evaluate and operate

on SFRs more efficiently. The Access RAM below 80h

is a good place for data values that the user might need

to access rapidly, such as immediate computational

results or common program variables. Access RAM

also allows for faster and more code efficient context

saving and switching of variables.

The mapping of the Access Bank is slightly different

when the extended instruction set is enabled (XINST

Configuration bit = 1). This is discussed in more detail

in Section 6.5.3 “Mapping the Access Bank in

Indexed Literal Offset Addressing Mode”.

6.3.3 GENERAL PURPOSE

PIC18 devices may have banked memory in the GPR

area. This is data RAM which is available for use by all

instructions. GPRs start at the bottom of Bank 0

(address 000h) and grow upwards towards the bottom of

the SFR area. GPRs are not initialized by a Power-on

Reset and are unchanged on all other Resets.

Note 1: The Access RAM bit of the instruction can be used to force an override of the selected bank (BSR<3:0>) to

the registers of the Access Bank.

2: The MOVFF instruction embeds the entire 12-bit address in the instruction.

Data Memory

Bank Select(2)

From Opcode(2)

0000 000h

100h

200h

F00h

FFFh

Bank 0

Bank 1

Bank 15

00h

FFh

00h

FFh

00h

FFh

Bank 2

through

Bank 14

0001 11111111

BSR(1)

PIC18F2221/2321/4221/4321 FAMILY

6.3.4 SPECIAL FUNCTION REGISTERS

The Special Function Registers (SFRs) are registers

used by the CPU and peripheral modules for controlling

the desired operation of the device. These registers are

implemented as static RAM. SFRs start at the top of

data memory (FFFh) and extend downward to occupy

the top half of Bank 15 (F80h to FFFh). A list of these

registers is given in Table 6-1 and Table 6-2.

The SFRs can be classified into two sets: those associ-

ated with the “core” device functionality (ALU, Resets

and interrupts) and those related to the peripheral

functions. The reset and interrupt registers are

described in their respective chapters, while the ALU’s

STATUS register is described later in this section.

Registers related to the operation of a peripheral feature

are described in the chapter for that peripheral.

The SFRs are typically distributed among the

peripherals whose functions they control. Unused SFR

locations are unimplemented and read as ‘0’s.

TABLE 6-1: SPECIAL FUNCTION REGISTER MAP FOR PIC18F2221/2321/4221/4321 FAMILY

DEVICES

Address Name Address Name Address Name Address Name

FFFh TOSU FDFh INDF2(1) FBFh CCPR1H F9Fh IPR1

FFEh TOSH FDEh POSTINC2(1) FBEh CCPR1L F9Eh PIR1

FFDh TOSL FDDh POSTDEC2(1) FBDh CCP1CON F9Dh PIE1

FFCh STKPTR FDCh PREINC2(1) FBCh CCPR2H F9Ch —(2)

FFBh PCLATU FDBh PLUSW2(1) FBBh CCPR2L F9Bh OSCTUNE

FFAh PCLATH FDAh FSR2H FBAh CCP2CON F9Ah —(2)

FF9h PCL FD9h FSR2L FB9h —(2) F99h —(2)

FF8h TBLPTRU FD8h STATUS FB8h BAUDCON F98h —(2)

FF7h TBLPTRH FD7h TMR0H FB7h ECCP1DEL(3) F97h —(2)

FF6h TBLPTRL FD6h TMR0L FB6h ECCP1AS(3) F96h TRISE(3)

FF5h TABLAT FD5h T0CON FB5h CVRCON F95h TRISD(3)

FF4h PRODH FD4h —(2) FB4h CMCON F94h TRISC

FF3h PRODL FD3h OSCCON FB3h TMR3H F93h TRISB

FF2h INTCON FD2h HLVDCON FB2h TMR3L F92h TRISA

FF1h INTCON2 FD1h WDTCON FB1h T3CON F91h —(2)

FF0h INTCON3 FD0h RCON FB0h SPBRGH F90h —(2)

FEFh INDF0(1) FCFh TMR1H FAFh SPBRG F8Fh —(2)

FEEh POSTINC0(1) FCEh TMR1L FAEh RCREG F8Eh —(2)

FEDh POSTDEC0(1) FCDh T1CON FADh TXREG F8Dh LATE(3)

FECh PREINC0(1) FCCh TMR2 FACh TXSTA F8Ch LATD(3)

FEBh PLUSW0(1) FCBh PR2 FABh RCSTA F8Bh LATC

FEAh FSR0H FCAh T2CON FAAh —(2) F8Ah LATB

FE9h FSR0L FC9h SSPBUF FA9h EEADR F89h LATA

FE8h WREG FC8h SSPADD FA8h EEDATA F88h —(2)

FE7h INDF1(1) FC7h SSPSTAT FA7h EECON2(1) F87h —(2)

FE6h POSTINC1(1) FC6h SSPCON1 FA6h EECON1 F86h —(2)

FE5h POSTDEC1(1) FC5h SSPCON2 FA5h —(2) F85h —(2)

FE4h PREINC1(1) FC4h ADRESH FA4h —(2) F84h PORTE

FE3h PLUSW1(1) FC3h ADRESL FA3h —(2) F83h PORTD(3)

FE2h FSR1H FC2h ADCON0 FA2h IPR2 F82h PORTC

FE1h FSR1L FC1h ADCON1 FA1h PIR2 F81h PORTB

FE0h BSR FC0h ADCON2 FA0h PIE2 F80h PORTA

Note 1: This is not a physical register.

2: Unimplemented registers are read as ‘0’.

3: This register is not available on 28-pin devices.

PIC18F2221/2321/4221/4321 FAMILY

TABLE 6-2: REGISTER FILE SUMMARY (PIC18F2221/2321/4221/4321)

File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on

POR, BOR

Details on

page:

TOSU — — — Top-of-Stack Upper Byte (TOS<20:16>) ---0 0000 55, 60

TOSH Top-of-Stack High Byte (TOS<15:8>) 0000 0000 55, 60

TOSL Top-of-Stack Low Byte (TOS<7:0>) 0000 0000 55, 60

STKPTR STKFUL(6) STKUNF(6) — SP4 SP3 SP2 SP1 SP0 00-0 0000 55, 61

PCLATU —— Holding Register for PC<21:16> --00 0000 55, 60

PCLATH Holding Register for PC<15:8> 0000 0000 55, 60

PCL PC Low Byte (PC<7:0>) 0000 0000 55, 60

TBLPTRU —— bit 21 Program Memory Table Pointer Upper Byte (TBLPTR<20:16>) --00 0000 55, 82

TBLPTRH Program Memory Table Pointer High Byte (TBLPTR<15:8>) 0000 0000 55, 82

TBLPTRL Program Memory Table Pointer Low Byte (TBLPTR<7:0>) 0000 0000 55, 82

TABLAT Program Memory Table Latch 0000 0000 55, 82

PRODH Product Register High Byte xxxx xxxx 55, 95

PRODL Product Register Low Byte xxxx xxxx 55, 95

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 0000 000x 55, 99

INTCON2 RBPU INTEDG0 INTEDG1 INTEDG2 —TMR0IP —RBIP1111 -1-1 55, 100

INTCON3 INT2IP INT1IP — INT2IE INT1IE — INT2IF INT1IF 11-0 0-00 55, 101

INDF0 Uses contents of FSR0 to address data memory – value of FSR0 not changed (not a physical register) N/A 55, 74

POSTINC0 Uses contents of FSR0 to address data memory – value of FSR0 post-incremented (not a physical register) N/A 55, 74

POSTDEC0 Uses contents of FSR0 to address data memory – value of FSR0 post-decremented (not a physical register) N/A 55, 74

PREINC0 Uses contents of FSR0 to address data memory – value of FSR0 pre-incremented (not a physical register) N/A 55, 74

PLUSW0 Uses contents of FSR0 to address data memory – value of FSR0 pre-incremented (not a physical register) –

value of FSR0 offset by W

N/A 55, 74

FSR0H — — — — Indirect Data Memory Address Pointer 0 High Byte ---- 0000 55, 74

FSR0L Indirect Data Memory Address Pointer 0 Low Byte xxxx xxxx 55, 74

WREG Working Register xxxx xxxx 55

INDF1 Uses contents of FSR1 to address data memory – value of FSR1 not changed (not a physical register) N/A 55, 74

POSTINC1 Uses contents of FSR1 to address data memory – value of FSR1 post-incremented (not a physical register) N/A 55, 74

POSTDEC1 Uses contents of FSR1 to address data memory – value of FSR1 post-decremented (not a physical register) N/A 55, 74

PREINC1 Uses contents of FSR1 to address data memory – value of FSR1 pre-incremented (not a physical register) N/A 55, 74

PLUSW1 Uses contents of FSR1 to address data memory – value of FSR1 pre-incremented (not a physical register) –

value of FSR1 offset by W

N/A 55, 74

FSR1H — — — — Indirect Data Memory Address Pointer 1 High Byte ---- 0000 56, 74

FSR1L Indirect Data Memory Address Pointer 1 Low Byte xxxx xxxx 56, 74

BSR — — — — Bank Select Register ---- 0000 56, 65

INDF2 Uses contents of FSR2 to address data memory – value of FSR2 not changed (not a physical register) N/A 56, 74

POSTINC2 Uses contents of FSR2 to address data memory – value of FSR2 post-incremented (not a physical register) N/A 56, 74

POSTDEC2 Uses contents of FSR2 to address data memory – value of FSR2 post-decremented (not a physical register) N/A 56, 74

PREINC2 Uses contents of FSR2 to address data memory – value of FSR2 pre-incremented (not a physical register) N/A 56, 74

PLUSW2 Uses contents of FSR2 to address data memory – value of FSR2 pre-incremented (not a physical register) –

value of FSR2 offset by W

N/A 56, 74

FSR2H — — — — Indirect Data Memory Address Pointer 2 High Byte ---- 0000 56, 74

FSR2L Indirect Data Memory Address Pointer 2 Low Byte xxxx xxxx 56, 74

STATUS — — —NOVZ DC C---x xxxx 56, 72

Legend: x = unknown, u = unchanged, — = unimplemented, q = value depends on condition

Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled and reads as ‘0’. See

Section 5.4 “Brown-out Reset (BOR)”.

2: These registers and/or bits are not implemented on 28-pin devices and are read as ‘0’. Reset values are shown for 40/44-pin devices;

individual unimplemented bits should be interpreted as ‘-’.

3: The PLLEN bit is only available in specific oscillator configurations; otherwise, it is disabled and reads as ‘0’. See Section 3.6.4 “PLL in

INTOSC Modes”.

4: The RE3 bit is only available when Master Clear Reset is disabled (MCLRE Configuration bit = 0); otherwise, RE3 reads as ‘0’. This bit is

read-only.

5: RA6/RA7 and their associated latch and direction bits are individually configured as port pins based on various primary oscillator modes.

When disabled, these bits read as ‘0’.

6: Bit 7 and bit 6 are cleared by user software or by a POR.

PIC18F2221/2321/4221/4321 FAMILY

TMR0H Timer0 Register High Byte 0000 0000 56, 131

TMR0L Timer0 Register Low Byte xxxx xxxx 56, 131

T0CON TMR0ON T08BIT T0CS T0SE PSA T0PS2 T0PS1 T0PS0 1111 1111 56, 129

OSCCON IDLEN IRCF2 IRCF1 IRCF0 OSTS IOFS SCS1 SCS0 0100 q000 37, 56

HLVDCON VDIRMAG — IRVST HLVDEN HLVDL3 HLVDL2 HLVDL1 HLVDL0 0-00 0101 56, 253

WDTCON — — — — — — —SWDTEN--- ---0 56, 270

RCON IPEN SBOREN(1) —RITO PD POR BOR 0q-1 11q0 48, 54, 108

TMR1H Timer1 Register High Byte xxxx xxxx 56, 137

TMR1L Timer1 Register Low Byte xxxx xxxx 56, 137

T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 0000 0000 56, 133

TMR2 Timer2 Register 0000 0000 56, 140

PR2 Timer2 Period Register 1111 1111 56, 140

T2CON — T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000 56, 139

SSPBUF MSSP Receive Buffer/Transmit Register xxxx xxxx 56, 175,

176

SSPADD MSSP Address Register in I2C™ Slave mode. MSSP Baud Rate Reload Register in I2C Master mode. 0000 0000 56, 176

SSPSTAT SMP CKE D/A PSR/WUA BF 0000 0000 56, 168,

177

SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 56, 169,

178

SSPCON2 GCEN ACKSTAT ACKDT/

ADMSK5

ACKEN/

ADMSK4

RCEN/

ADMSK3

PEN/

ADMSK2

RSEN/

ADMSK1

SEN 0000 0000 56, 179

ADRESH A/D Result Register High Byte xxxx xxxx 57, 242

ADRESL A/D Result Register Low Byte xxxx xxxx 57, 242

ADCON0 —— CHS3 CHS2 CHS1 CHS0 GO/DONE ADON --00 0000 57, 233

ADCON1 —— VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 --00 0qqq 57, 234

ADCON2 ADFM — ACQT2 ACQT1 ACQT0 ADCS2 ADCS1 ADCS0 0-00 0000 57, 235

CCPR1H Capture/Compare/PWM Register 1 High Byte xxxx xxxx 57, 146

CCPR1L Capture/Compare/PWM Register 1 Low Byte xxxx xxxx 57, 146

CCP1CON P1M1(2) P1M0(2) DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 0000 0000 57, 145,

153

CCPR2H Capture/Compare/PWM Register 2 High Byte xxxx xxxx 57, 146

CCPR2L Capture/Compare/PWM Register 2 Low Byte xxxx xxxx 57, 146

CCP2CON —— DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 --00 0000 57, 145

BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN 0100 0-00 57, 214

ECCP1DEL PRSEN PDC6(2) PDC5(2) PDC4(2) PDC3(2) PDC2(2) PDC1(2) PDC0(2) 0000 0000 57, 162

ECCP1AS ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1(2) PSSBD0(2) 0000 0000 57, 163

CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 0000 0000 57, 249

CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 0000 0111 57, 243

TMR3H Timer3 Register High Byte xxxx xxxx 57, 143

TMR3L Timer3 Register Low Byte xxxx xxxx 57, 143

T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 0000 0000 57, 141

TABLE 6-2: REGISTER FILE SUMMARY (PIC18F2221/2321/4221/4321) (CONTINUED)

File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on

POR, BOR

Details on

page:

Legend: x = unknown, u = unchanged, — = unimplemented, q = value depends on condition

Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled and reads as ‘0’. See

Section 5.4 “Brown-out Reset (BOR)”.

2: These registers and/or bits are not implemented on 28-pin devices and are read as ‘0’. Reset values are shown for 40/44-pin devices;

individual unimplemented bits should be interpreted as ‘-’.

3: The PLLEN bit is only available in specific oscillator configurations; otherwise, it is disabled and reads as ‘0’. See Section 3.6.4 “PLL in

INTOSC Modes”.

4: The RE3 bit is only available when Master Clear Reset is disabled (MCLRE Configuration bit = 0); otherwise, RE3 reads as ‘0’. This bit is

read-only.

5: RA6/RA7 and their associated latch and direction bits are individually configured as port pins based on various primary oscillator modes.

When disabled, these bits read as ‘0’.

6: Bit 7 and bit 6 are cleared by user software or by a POR.

PIC18F2221/2321/4221/4321 FAMILY

SPBRGH EUSART Baud Rate Generator Register High Byte 0000 0000 57, 216

SPBRG EUSART Baud Rate Generator Register Low Byte 0000 0000 57, 216

RCREG EUSART Receive Register 0000 0000 57, 224

TXREG EUSART Transmit Register 0000 0000 57, 221

TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 0000 0010 57, 212

RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 0000 000x 57, 213

EEADR EEPROM Address Register 0000 0000 57, 80, 89

EEDATA EEPROM Data Register 0000 0000 57, 80, 89

EECON2 EEPROM Control Register 2 (not a physical register) 0000 0000 57, 80, 89

EECON1 EEPGD CFGS — FREE WRERR WREN WR RD xx-0 x000 57, 81, 90

IPR2 OSCFIP CMIP — EEIP BCLIP HLVDIP TMR3IP CCP2IP 11-1 1111 58, 107

PIR2 OSCFIF CMIF — EEIF BCLIF HLVDIF TMR3IF CCP2IF 00-0 0000 58, 103

PIE2 OSCFIE CMIE — EEIE BCLIE HLVDIE TMR3IE CCP2IE 00-0 0000 58, 105

IPR1 PSPIP(2) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 1111 1111 58, 106

PIR1 PSPIF(2) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 58, 102

PIE1 PSPIE(2) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 0000 0000 58, 104

OSCTUNE INTSRC PLLEN(3) — TUN4 TUN3 TUN2 TUN1 TUN0 00-0 0000 33, 58

TRISE(2) IBF OBF IBOV PSPMODE — TRISE2 TRISE1 TRISE0 0000 -111 58, 124

TRISD(2) PORTD Data Direction Control Register 1111 1111 58, 120

TRISC PORTC Data Direction Control Register 1111 1111 58, 117

TRISB PORTB Data Direction Control Register 1111 1111 58, 114

TRISA TRISA7(5) TRISA6(5) PORTA Data Direction Control Register 1111 1111 58, 111

LATE(2) — — — — — PORTE Data Latch Register

(Read and Write to Data Latch)

---- -xxx 58, 123

LATD(2) PORTD Data Latch Register (Read and Write to Data Latch) xxxx xxxx 58, 120

LATC PORTC Data Latch Register (Read and Write to Data Latch) xxxx xxxx 58, 117

LATB PORTB Data Latch Register (Read and Write to Data Latch) xxxx xxxx 58, 114

LATA LATA7(5) LATA6(5) PORTA Data Latch Register (Read and Write to Data Latch) xxxx xxxx 58, 111

PORTE — — — —RE3

(4) RE2(2) RE1(2) RE0(2) ---- xxxx 58, 123

PORTD(2) RD7 RD6 RD5 RD4 RD3 RD2 RD1 RD0 xxxx xxxx 58, 120

PORTC RC7 RC6 RC5 RC4 RC3 RC2 RC1 RC0 xxxx xxxx 58, 117

PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 xxxx xxxx 58, 114

PORTA RA7(5) RA6(5) RA5 RA4 RA3 RA2 RA1 RA0 xx0x 0000 58, 111

TABLE 6-2: REGISTER FILE SUMMARY (PIC18F2221/2321/4221/4321) (CONTINUED)

File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on

POR, BOR

Details on

page:

Legend: x = unknown, u = unchanged, — = unimplemented, q = value depends on condition

Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled and reads as ‘0’. See

Section 5.4 “Brown-out Reset (BOR)”.

2: These registers and/or bits are not implemented on 28-pin devices and are read as ‘0’. Reset values are shown for 40/44-pin devices;

individual unimplemented bits should be interpreted as ‘-’.

3: The PLLEN bit is only available in specific oscillator configurations; otherwise, it is disabled and reads as ‘0’. See Section 3.6.4 “PLL in

INTOSC Modes”.

4: The RE3 bit is only available when Master Clear Reset is disabled (MCLRE Configuration bit = 0); otherwise, RE3 reads as ‘0’. This bit is

read-only.

5: RA6/RA7 and their associated latch and direction bits are individually configured as port pins based on various primary oscillator modes.

When disabled, these bits read as ‘0’.

6: Bit 7 and bit 6 are cleared by user software or by a POR.

PIC18F2221/2321/4221/4321 FAMILY

6.3.5 STATUS REGISTER

The STATUS register, shown in Register 6-2, contains

the arithmetic status of the ALU. As with any other SFR,

it can be the operand for any instruction.

If the STATUS register is the destination for an instruc-

tion that affects the Z, DC, C, OV or N bits, the results

of the instruction are not written; instead, the STATUS

performed. Therefore, the result of an instruction with

the STATUS register as its destination may be different

than intended. As an example, CLRF STATUS will set

the Z bit and leave the remaining Status bits

unchanged (‘000u u1uu’).

It is recommended that only BCF, BSF, SWAPF, MOVFF

and MOVWF instructions are used to alter the STATUS

C, DC, OV or N bits in the STATUS register.

For other instructions that do not affect Status bits, see

the instruction set summaries in Table 24-2 and

Table 24-3.

Note: The C and DC bits operate as the borrow

and digit borrow bits, respectively, in

subtraction.

U-0 U-0 U-0 R/W-x R/W-x R/W-x R/W-x R/W-x

— — —NOVZDCC

bit 7 bit 0

bit 7-5 Unimplemented: Read as ‘0’

bit 4 N: Negative bit

This bit is used for signed arithmetic (2’s complement). It indicates whether the result was

negative (ALU MSB = 1).

1 = Result was negative

0 = Result was positive

bit 3 OV: Overflow bit

This bit is used for signed arithmetic (2’s complement). It indicates an overflow of the 7-bit

magnitude which causes the sign bit (bit 7 of the result) to change state.

1 = Overflow occurred for signed arithmetic (in this arithmetic operation)

0 = No overflow occurred

bit 2 Z: Zero bit

1 = The result of an arithmetic or logic operation is zero

0 = The result of an arithmetic or logic operation is not zero

bit 1 DC: Digit Carry/borrow bit

For ADDWF, ADDLW, SUBLW and SUBWF instructions:

1 = A carry-out from the 4th low-order bit of the result occurred

0 = No carry-out from the 4th low-order bit of the result

Note: For borrow, the polarity is reversed. A subtraction is executed by adding the 2’s

complement of the second operand. For rotate (RRF, RLF) instructions, this bit is

loaded with either bit 4 or bit 3 of the source register.

bit 0 C: Carry/borrow bit

For ADDWF, ADDLW, SUBLW and SUBWF instructions:

1 = A carry-out from the Most Significant bit of the result occurred

0 = No carry-out from the Most Significant bit of the result occurred

Note: For borrow, the polarity is reversed. A subtraction is executed by adding the 2’s

complement of the second operand. For rotate (RRF, RLF) instructions, this bit is

loaded with either the high or low-order bit of the source register.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

6.4 Data Addressing Modes

The data memory space can be addressed in several

ways. For most instructions, the addressing mode is

fixed. Other instructions may use up to three modes,

depending on which operands are used and whether or

not the extended instruction set is enabled.

The addressing modes are:

• Inherent

• Literal

•Direct

•Indirect

An additional addressing mode, Indexed Literal Offset,

is available when the extended instruction set is

enabled (XINST Configuration bit = 1). Its operation is

discussed in greater detail in Section 6.5.1 “Indexed

Addressing with Literal Offset”.

6.4.1 INHERENT AND LITERAL

ADDRESSING

Many PIC18 control instructions do not need any

argument at all; they either perform an operation that

globally affects the device or they operate implicitly on

one register. This addressing mode is known as Inherent

Addressing. Examples include SLEEP, RESET and DAW.

Other instructions work in a similar way but require an

additional explicit argument in the opcode. This is

known as Literal Addressing mode because they

require some literal value as an argument. Examples

include ADDLW and MOVLW, which respectively, add or

move a literal value to the W register. Other examples

include CALL and GOTO, which include a 20-bit

program memory address.

6.4.2 DIRECT ADDRESSING

Direct addressing specifies all or part of the source

and/or destination address of the operation within the

opcode itself. The options are specified by the

arguments accompanying the instruction.

In the core PIC18 instruction set, bit-oriented and byte-

oriented instructions use some version of direct

addressing by default. All of these instructions include

some 8-bit literal address as their Least Significant

Byte. This address specifies either a register address in

one of the banks of data RAM (Section 6.3.3 “General

Purpose Register File”) or a location in the Access

Bank (Section 6.3.2 “Access Bank”) as the data

source for the instruction.

The Access RAM bit ‘a’ determines how the address is

interpreted. When ‘a’ is ‘1’, the contents of the BSR

(Section 6.3.1 “Bank Select Register (BSR)”) are

used with the address to determine the complete 12-bit

address of the register. When ‘a’ is ‘0’, the address is

interpreted as being a register in the Access Bank.

Addressing that uses the Access RAM is sometimes

also known as Direct Forced Addressing mode.

A few instructions, such as MOVFF, include the entire

12-bit address (either source or destination) in their

opcodes. In these cases, the BSR is ignored entirely.

The destination of the operation’s results is determined

by the destination bit ‘d’. When ‘d’ is ‘1’, the results are

stored back in the source register, overwriting its origi-

nal contents. When ‘d’ is ‘0’, the results are stored in

the W register. Instructions without the ‘d’ argument

have a destination that is implicit in the instruction; their

destination is either the target register being operated

on or the W register.

6.4.3 INDIRECT ADDRESSING

Indirect addressing allows the user to access a location

in data memory without giving a fixed address in the

instruction. This is done by using File Select Registers

(FSRs) as pointers to the locations to be read or written

to. Since the FSRs are themselves located in RAM as

Special Function Registers, they can also be directly

manipulated under program control. This makes FSRs

very useful in implementing data structures, such as

tables and arrays in data memory.

The registers for indirect addressing are also

implemented with Indirect File Operands (INDFs) that

permit automatic manipulation of the pointer value with

auto-incrementing, auto-decrementing or offsetting

with another value. This allows for efficient code, using

loops, such as the example of clearing an entire RAM

bank in Example 6-5.

EXAMPLE 6-5: HOW TO CLEAR RAM

(BANK 1) USING

INDIRECT ADDRESSING

Note: The execution of some instructions in the

core PIC18 instruction set are changed

when the PIC18 extended instruction set is

enabled. See Section 6.5 “Data Memory

and the Extended Instruction Set” for

more information.

LFSR FSR0, 100h ;

NEXT CLRF POSTINC0 ; Clear INDF

; register then

; inc pointer

BTFSS FSR0H, 1 ; All done with

; Bank1?

BRA NEXT ; NO, clear next

CONTINUE ; YES, continue

PIC18F2221/2321/4221/4321 FAMILY

6.4.3.1 FSR Registers and the

INDF Operand

At the core of indirect addressing are three sets of

registers: FSR0, FSR1 and FSR2. Each represents a

pair of 8-bit registers, FSRnH and FSRnL. The four

upper bits of the FSRnH register are not used so each

FSR pair holds a 12-bit value. This represents a value

that can address the entire range of the data memory

in a linear fashion. The FSR register pairs, then, serve

as pointers to data memory locations.

Indirect addressing is accomplished with a set of

Indirect File Operands, INDF0 through INDF2. These

can be thought of as “virtual” registers: they are

mapped in the SFR space but are not physically imple-

mented. Reading or writing to a particular INDF register

actually accesses its corresponding FSR register pair.

A read from INDF1, for example, reads the data at the

address indicated by FSR1H:FSR1L. Instructions that

use the INDF registers as operands actually use the

contents of their corresponding FSR as a pointer to the

instruction’s target. The INDF operand is just a

convenient way of using the pointer.

Because indirect addressing uses a full 12-bit address,

data RAM banking is not necessary. Thus, the current

contents of the BSR and the Access RAM bit have no

effect on determining the target address.

6.4.3.2 FSR Registers and POSTINC,

POSTDEC, PREINC and PLUSW

In addition to the INDF operand, each FSR register pair

also has four additional indirect operands. Like INDF,

these are “virtual” registers that cannot be indirectly

read or written to. Accessing these registers actually

accesses the associated FSR register pair, but also

performs a specific action on its stored value. They are:

• POSTDEC: accesses the FSR value, then

automatically decrements it by 1 afterwards

• POSTINC: accesses the FSR value, then

automatically increments it by 1 afterwards

• PREINC: increments the FSR value by 1, then

uses it in the operation

• PLUSW: adds the signed value of the W register

(range of -127 to 128) to that of the FSR and uses

the new value in the operation.

In this context, accessing an INDF register uses the

value in the FSR registers without changing them. Sim-

ilarly, accessing a PLUSW register gives the FSR value

offset by that in the W register; neither value is actually

changed in the operation. Accessing the other virtual

registers changes the value of the FSR registers.

Operations on the FSRs with POSTDEC, POSTINC

and PREINC affect the entire register pair; that is, roll-

overs of the FSRnL register from FFh to 00h carry over

to the FSRnH register. On the other hand, results of

these operations do not change the value of any flags

in the STATUS register (e.g., Z, N, OV, etc.).

FIGURE 6-7: INDIRECT ADDRESSING

FSR1H:FSR1L

Data Memory

000h

100h

200h

300h

F00h

E00h

FFFh

Bank 0

Bank 1

Bank 2

Bank 14

Bank 15

Bank 3

through

Bank 13

ADDWF, INDF1, 1

Using an instruction with one of the

indirect addressing registers as the

operand....

...uses the 12-bit address stored in

the FSR pair associated with that

...to determine the data memory

location to be used in that operation.

In this case, the FSR1 pair contains

ECCh. This means the contents of

location ECCh will be added to that

of the W register and stored back in

ECCh.

xxxx1110 11001100

PIC18F2221/2321/4221/4321 FAMILY

The PLUSW register can be used to implement a form

of indexed addressing in the data memory space. By

manipulating the value in the W register, users can

reach addresses that are fixed offsets from pointer

addresses. In some applications, this can be used to

implement some powerful program control structure,

such as software stacks, inside of data memory.

6.4.3.3 Operations by FSRs on FSRs

Indirect addressing operations that target other FSRs or

virtual registers represent special cases. For example,

using an FSR to point to one of the virtual registers will

not result in successful operations. As a specific case,

assume that FSR0H:FSR0L contains FE7h, the address

of INDF1. Attempts to read the value of the INDF1 using

INDF0 as an operand will return 00h. Attempts to write

to INDF1 using INDF0 as the operand will result in a NOP.

On the other hand, using the virtual registers to write to

an FSR pair may not occur as planned. In these cases,

the value will be written to the FSR pair but without any

incrementing or decrementing. Thus, writing to INDF2

or POSTDEC2 will write the same value to the

FSR2H:FSR2L.

Since the FSRs are physical registers mapped in the

SFR space, they can be manipulated through all direct

operations. Users should proceed cautiously when

working on these registers, particularly if their code

uses indirect addressing.

Similarly, operations by indirect addressing are generally

permitted on all other SFRs. Users should exercise the

appropriate caution that they do not inadvertently

change settings that might affect the operation of the

device.

6.5 Data Memory and the Extended

Instruction Set

Enabling the PIC18 extended instruction set (XINST

Configuration bit = 1) significantly changes certain

aspects of data memory and its addressing. Specifically,

the use of the Access Bank for many of the core PIC18

instructions is different. This is due to the introduction of

a new addressing mode for the data memory space.

What does not change is just as important. The size of

the data memory space is unchanged, as well as its

linear addressing. The SFR map remains the same.

Core PIC18 instructions can still operate in both Direct

and Indirect Addressing mode; inherent and literal

instructions do not change at all. Indirect addressing

with FSR0 and FSR1 also remain unchanged.

6.5.1 INDEXED ADDRESSING WITH

LITERAL OFFSET

Enabling the PIC18 extended instruction set changes

the behavior of indirect addressing using the FSR2

conditions, instructions that use the Access Bank – that

is, most bit-oriented and byte-oriented instructions – can

invoke a form of indexed addressing using an offset

specified in the instruction. This special addressing

mode is known as Indexed Addressing with Literal

Offset, or Indexed Literal Offset mode.

When using the extended instruction set, this

addressing mode requires the following:

• The use of the Access Bank is forced (‘a’ = 0);

and

• The file address argument is less than or equal to

5Fh.

Under these conditions, the file address of the instruc-

tion is not interpreted as the lower byte of an address

(used with the BSR in direct addressing), or as an 8-bit

address in the Access Bank. Instead, the value is

interpreted as an offset value to an Address Pointer,

specified by FSR2. The offset and the contents of

FSR2 are added to obtain the target address of the

operation.

6.5.2 INSTRUCTIONS AFFECTED BY

INDEXED LITERAL OFFSET MODE

Any of the core PIC18 instructions that can use direct

addressing are potentially affected by the Indexed

Literal Offset Addressing mode. This includes all

byte-oriented and bit-oriented instructions, or almost

one-half of the standard PIC18 instruction set.

Instructions that only use Inherent or Literal Addressing

modes are unaffected.

Additionally, byte-oriented and bit-oriented instructions

are not affected if they do not use the Access Bank

(Access RAM bit is ‘1’), or include a file address of 60h

or above. Instructions meeting these criteria will

continue to execute as before. A comparison of the dif-

ferent possible addressing modes when the extended

instruction set is enabled is shown in Figure 6-8.

Those who desire to use bit-oriented or byte-oriented

instructions in the Indexed Literal Offset mode should

note the changes to assembler syntax for this mode.

This is described in more detail in Section 24.2.1

“Extended Instruction Syntax”.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 6-8: COMPARING ADDRESSING OPTIONS FOR BIT-ORIENTED AND

BYTE-ORIENTED INSTRUCTIONS (EXTENDED INSTRUCTION SET ENABLED)

EXAMPLE INSTRUCTION: ADDWF, f, d, a (Opcode: 0010 01da ffff ffff)

When ‘a’ = 0 and ‘f’ ≥ 60h:

The instruction executes in

Direct Forced mode. ‘f’ is inter-

preted as a location in the

Access RAM between 060h

and 0FFh. This is the same as

locations 060h to 07Fh

(Bank 0) and F80h to FFFh

(Bank 15) of data memory.

Locations below 60h are not

available in this addressing

mode.

When ‘a’ = 0 and ‘f’ ≤ 5Fh:

The instruction executes in

Indexed Literal Offset mode. ‘f’

is interpreted as an offset to the

address value in FSR2. The

two are added together to

obtain the address of the target

address can be anywhere in

the data memory space.

Note that in this mode, the

correct syntax is now:

ADDWF [k], d

where ‘k’ is the same as ‘f’.

When ‘a’ = 1 (all values of ‘f’):

The instruction executes in

Direct mode (also known as

Direct Long mode). ‘f’ is inter-

preted as a location in one of

the 16 banks of the data

memory space. The bank is

designated by the Bank Select

can be in any implemented

bank in the data memory

space.

000h

060h

100h

F00h

F80h

FFFh

Valid range

00h

60h

80h

FFh

Data Memory

Access RAM

Bank 0

Bank 1

through

Bank 14

Bank 15

SFRs

000h

080h

100h

F00h

F80h

FFFh

Data Memory

Bank 0

Bank 1

through

Bank 14

Bank 15

SFRs

FSR2H FSR2L

ffffffff001001da

000h

080h

100h

F00h

F80h

FFFh

Data Memory

Bank 0

Bank 1

through

Bank 14

Bank 15

SFRs

for ‘f’

BSR

00000000

080h

PIC18F2221/2321/4221/4321 FAMILY

6.5.3 MAPPING THE ACCESS BANK IN

INDEXED LITERAL OFFSET

ADDRESSING MODE

The use of Indexed Literal Offset Addressing mode

effectively changes how the first 96 locations of Access

RAM (00h to 5Fh) are mapped. Rather than containing

just the contents of the bottom half of Bank 0, this mode

maps the contents from Bank 0 and a user-defined

“window” that can be located anywhere in the data

memory space. The value of FSR2 establishes the

lower boundary of the addresses mapped into the

window, while the upper boundary is defined by FSR2

plus 95 (5Fh). Addresses in the Access RAM above

5Fh are mapped as previously described (see

Section 6.3.2 “Access Bank”). An example of Access

Bank remapping in this addressing mode is shown in

Figure 6-9.

Remapping of the Access Bank applies only to opera-

tions using the Indexed Literal Offset Addressing

mode. Operations that use the BSR (Access RAM bit is

‘1’) will continue to use direct addressing as before.

6.6 PIC18 Instruction Execution and

the Extended Instruction Set

Enabling the extended instruction set adds eight

additional commands to the existing PIC18 instruction

set. These instructions are executed as described in

Section 24.2 “Extended Instruction Set”.

FIGURE 6-9: REMAPPING THE ACCESS BANK WITH INDEXED LITERAL OFFSET

ADDRESSING MODE

Data Memory

000h

100h

200h

F80h

F00h

FFFh

Bank 1

Bank 15

Bank 2

through

Bank 14

SFRs

05Fh

ADDWF f, d, a

FSR2H:FSR2L = 120h

Locations in the region

from the FSR2 Pointer

(120h) to the pointer plus

05Fh (17Fh) are mapped

to the bottom of the

Access RAM (000h-05Fh).

Locations in Bank 0, from

060h to 07Fh, are mapped

as usual to the middle of

the Access Bank.

Special Function Regis-

ters at F80h through FFFh

are mapped to 80h

through FFh, as usual.

Bank 0 addresses below

5Fh can still be addressed

by using the BSR.

Access Bank

00h

80h

FFh

7Fh

Bank 0

SFRs

Bank 1 “Window”

Bank 0

Window

Example Situation:

07Fh

120h

17Fh

5Fh

Bank 1

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

7.0 FLASH PROGRAM MEMORY

The Flash program memory is readable, writable and

erasable during normal operation over the entire VDD

range.

A read from program memory is executed on one byte

at a time. A write to program memory is executed on

blocks of 8 bytes at a time. Program memory is erased

in blocks of 64 bytes at a time. A bulk erase operation

may not be issued from user code.

Writing or erasing program memory will cease

instruction fetches until the operation is complete. The

program memory cannot be accessed during the write

or erase, therefore, code cannot execute. An internal

programming timer terminates program memory writes

and erases.

A value written to program memory does not need to be

a valid instruction. Executing a program memory

location that forms an invalid instruction results in a

NOP.

7.1 Table Reads and Table Writes

In order to read and write program memory, there are

two operations that allow the processor to move bytes

between the program memory space and the data RAM:

• Table Read (TBLRD)

• Table Write (TBLWT)

The program memory space is 16 bits wide, while the

data RAM space is 8 bits wide. Table reads and table

writes move data between these two memory spaces

through an 8-bit register (TABLAT).

Table read operations retrieve data from program

memory and place it into the data RAM space.

Figure 7-1 shows the operation of a table read with

program memory and data RAM.

Table write operations store data from the data memory

space into holding registers in program memory. The

procedure to write the contents of the holding registers

into program memory is detailed in Section 7.5 “Writing

to Flash Program Memory”. Figure 7-2 shows the

operation of a table write with program memory and data

RAM.

Table operations work with byte entities. A table block

containing data, rather than program instructions, is not

required to be word-aligned. Therefore, a table block can

start and end at any byte address. If a table write is being

used to write executable code into program memory,

program instructions will need to be word-aligned.

FIGURE 7-1: TABLE READ OPERATION

Table Pointer(1)

Table Latch (8-bit)

Program Memory

TBLPTRH TBLPTRL

TABLAT

TBLPTRU

Instruction: TBLRD*

Note 1: Table Pointer register points to a byte in program memory.

Program Memory

(TBLPTR)

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 7-2: TABLE WRITE OPERATION

7.2 Control Registers

Several control registers are used in conjunction with

the TBLRD and TBLWT instructions. These include the:

• EECON1 register

• EECON2 register

• TABLAT register

• TBLPTR registers

7.2.1 EECON1 AND EECON2 REGISTERS

The EECON1 register (Register 7-1) is the control

not a physical register; it is used exclusively in the

memory write and erase sequences. Reading

EECON2 will read all ‘0’s.

The EEPGD control bit determines if the access will be

a program or data EEPROM memory access. When

clear, any subsequent operations will operate on the

data EEPROM memory. When set, any subsequent

operations will operate on the program memory.

The CFGS control bit determines if the access will be

to the Configuration/Calibration registers or to program

memory/data EEPROM memory. When set,

subsequent operations will operate on Configuration

registers regardless of EEPGD (see Section 24.0

“Special Features of the CPU”). When clear, memory

selection access is determined by EEPGD.

The FREE bit, when set, will allow a program memory

erase operation. When FREE is set, the erase

operation is initiated on the next WR command. When

FREE is clear, only writes are enabled.

The WREN bit, when set, will allow a write operation.

On power-up, the WREN bit is clear. The WRERR bit is

set in hardware when the WR bit is set and cleared

when the internal programming timer expires and the

write operation is complete.

The WR control bit initiates write operations. The bit

cannot be cleared, only set, in software; it is cleared in

hardware at the completion of the write operation.

Tab l e P oi n te r (1) Table Latch (8-bit)

TBLPTRH TBLPTRL TABLAT

Program Memory

(TBLPTR)

TBLPTRU

Instruction: TBLWT*

Note 1: Table Pointer actually points to one of 64 holding registers, the address of which is determined by

TBLPTRL<5:0>. The process for physically writing data to the program memory array is discussed in

Section 7.5 “Writing to Flash Program Memory”.

Holding Registers

Program Memory

Note: During normal operation, the WRERR bit

may read as ‘1’. This can indicate that a

write operation was prematurely termi-

nated by a Reset, or a write operation was

attempted improperly.

Note: The EEIF interrupt flag bit (PIR2<4>) is set

when the write is complete. It must be

cleared in software.

PIC18F2221/2321/4221/4321 FAMILY

R/W-x R/W-x U-0 R/W-0 R/W-x R/W-0 R/S-0 R/S-0

EEPGD CFGS — FREE WRERR WREN WR RD

bit 7 bit 0

bit 7 EEPGD: Flash Program or Data EEPROM Memory Select bit

1 = Access Flash program memory

0 = Access data EEPROM memory

bit 6 CFGS: Flash Program/Data EEPROM or Configuration Select bit

1 = Access Configuration registers

0 = Access Flash program or data EEPROM memory

bit 5 Unimplemented: Read as ‘0’

bit 4 FREE: Flash Row Erase Enable bit

1 = Erase the program memory row addressed by TBLPTR on the next WR command

(cleared by completion of erase operation)

0 = Perform write-only

bit 3 WRERR: Flash Program/Data EEPROM Error Flag bit

1 = A write operation is prematurely terminated (any Reset during self-timed programming in

normal operation, or an improper write attempt)

0 = The write operation completed

Note: When a WRERR occurs, the EEPGD and CFGS bits are not cleared.

This allows tracing of the error condition.

bit 2 WREN: Flash Program/Data EEPROM Write Enable bit

1 = Allows write cycles to Flash program/data EEPROM

0 = Inhibits write cycles to Flash program/data EEPROM

bit 1 WR: Write Control bit

1 = Initiates a data EEPROM erase/write cycle or a program memory erase/write cycle.

(The operation is self-timed and the bit is cleared by hardware once write is complete.

The WR bit can only be set (not cleared) in software.)

0 = Write cycle to the EEPROM is complete

bit 0 RD: Read Control bit

1 = Initiates an EEPROM read (Read takes one cycle. RD is cleared in hardware. The RD bit can

only be set (not cleared) in software. RD bit cannot be set when EEPGD = 1 or CFGS = 1.)

0 = Does not initiate an EEPROM read

Legend:

R = Readable bit W = Writable bit

S = Bit can be set by software, but not cleared U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

7.2.2 TABLAT – TABLE LATCH REGISTER

The Table Latch (TABLAT) is an 8-bit register mapped

into the SFR space. The Table Latch register is used to

hold 8-bit data during data transfers between program

memory and data RAM.

7.2.3 TBLPTR – TABLE POINTER

The Table Pointer (TBLPTR) register addresses a byte

within the program memory. The TBLPTR is comprised

of three SFR registers: Table Pointer Upper Byte, Table

Pointer High Byte and Table Pointer Low Byte

(TBLPTRU:TBLPTRH:TBLPTRL). These three regis-

ters join to form a 22-bit wide pointer. The low-order

21 bits allow the device to address up to 2 Mbytes of

program memory space. The 22nd bit allows access to

the device ID, the user ID and the Configuration bits.

The Table Pointer register, TBLPTR, is used by the

TBLRD and TBLWT instructions. These instructions can

update the TBLPTR in one of four ways based on the

table operation. These operations are shown in

Table 7-1. These operations on the TBLPTR only affect

the low-order 21 bits.

7.2.4 TABLE POINTER BOUNDARIES

TBLPTR is used in reads, writes and erases of the

Flash program memory.

When a TBLRD is executed, all 22 bits of the TBLPTR

determine which byte is read from program memory

into TABLAT.

When the timed write to program memory begins (via

the WR bit), the 19 MSbs of the TBLPTR

(TBLPTR<21:3>) determine which program memory

block of 8 bytes is written to. The Table Pointer regis-

ter’s three LSBs (TBLPTR<2:0>) are ignored. For more

detail, see Section 7.5 “Writing to Flash Program

Memory”.

When an erase of program memory is executed, the

16 MSbs of the Table Pointer register (TBLPTR<21:6>)

point to the 64-byte block that will be erased. The Least

Significant bits (TBLPTR<5:0>) are ignored.

Figure 7-3 describes the relevant boundaries of

TBLPTR based on Flash program memory operations.

TABLE 7-1: TABLE POINTER OPERATIONS WITH TBLRD AND TBLWT INSTRUCTIONS

FIGURE 7-3: TABLE POINTER BOUNDARIES BASED ON OPERATION

Example Operation on Table Pointer

TBLRD*

TBLWT* TBLPTR is not modified

TBLRD*+

TBLWT*+ TBLPTR is incremented after the read/write

TBLRD*-

TBLWT*- TBLPTR is decremented after the read/write

TBLRD+*

TBLWT+* TBLPTR is incremented before the read/write

21 16 15 87 0

TABLE ERASE

TABLE WRITE

TABLE READ – TBLPTR<21:0>

TBLPTRL

TBLPTRH

TBLPTRU

TBLPTR<21:3>

TBLPTR<21:6>

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7.3 Reading the Flash Program

Memory

The TBLRD instruction is used to retrieve data from

program memory and place it into data RAM. Table

reads from program memory are performed one byte at

a time.

TBLPTR points to a byte address in program space.

Executing TBLRD places the byte pointed to into

TABLAT. In addition, TBLPTR can be modified

automatically for the next table read operation.

The internal program memory is typically organized by

words. The Least Significant bit of the address selects

between the high and low bytes of the word. Figure 7-4

shows the interface between the internal program

memory and the TABLAT.

FIGURE 7-4: READS FROM FLASH PROGRAM MEMORY

EXAMPLE 7-1: READING A FLASH PROGRAM MEMORY WORD

(Even Byte Address)

Program Memory

(Odd Byte Address)

TBLRD TABLAT

TBLPTR = xxxxx1

FETCH

Instruction Register

(IR) Read Register

TBLPTR = xxxxx0

MOVLW CODE_ADDR_UPPER ; Load TBLPTR with the base

MOVWF TBLPTRU ; address of the word

MOVLW CODE_ADDR_HIGH

MOVWF TBLPTRH

MOVLW CODE_ADDR_LOW

MOVWF TBLPTRL

READ_WORD

TBLRD*+ ; read into TABLAT and increment

MOVF TABLAT, W ; get data

MOVWF WORD_EVEN

TBLRD*+ ; read into TABLAT and increment

MOVF TABLAT, W ; get data

MOVWF WORD_ODD

PIC18F2221/2321/4221/4321 FAMILY

7.4 Erasing Flash Program Memory

The minimum erase block is 32 words or 64 bytes. Only

through the use of an external programmer, or through

ICSP control, can larger blocks of program memory be

bulk erased. Word erase in the Flash array is not

supported.

When initiating an erase sequence from the micro-

controller itself, a block of 64 bytes of program memory

is erased. The Most Significant 16 bits of the

TBLPTR<21:6> point to the block being erased.

TBLPTR<5:0> are ignored.

The EECON1 register commands the erase operation.

The EEPGD bit must be set to point to the Flash

program memory. The WREN bit must be set to enable

write operations. The FREE bit is set to select an erase

operation.

For protection, the write initiate sequence for EECON2

must be used.

A long write is necessary for erasing the internal Flash.

Instruction execution is halted while in a long write

cycle. The long write will be terminated by the internal

programming timer.

7.4.1 FLASH PROGRAM MEMORY

ERASE SEQUENCE

The sequence of events for erasing a block of internal

program memory location is:

1. Load Table Pointer register with address of row

being erased.

2. Set the EECON1 register for the erase operation:

• set EEPGD bit to point to program memory;

• clear the CFGS bit to access program memory;

• set WREN bit to enable writes;

• set FREE bit to enable the erase.

3. Disable interrupts.

4. Write 55h to EECON2.

5. Write 0AAh to EECON2.

6. Set the WR bit. This will begin the row erase

cycle.

7. The CPU will stall for duration of the erase

(about 2 ms using internal timer).

8. Re-enable interrupts.

EXAMPLE 7-2: ERASING A FLASH PROGRAM MEMORY ROW

MOVLW CODE_ADDR_UPPER ; load TBLPTR with the base

MOVWF TBLPTRU ; address of the memory block

MOVLW CODE_ADDR_HIGH

MOVWF TBLPTRH

MOVLW CODE_ADDR_LOW

MOVWF TBLPTRL

ERASE_ROW

BSF EECON1, EEPGD ; point to Flash program memory

BCF EECON1, CFGS ; access Flash program memory

BSF EECON1, WREN ; enable write to memory

BSF EECON1, FREE ; enable Row Erase operation

BCF INTCON, GIE ; disable interrupts

Required MOVLW 55h

Sequence MOVWF EECON2 ; write 55h

MOVLW 0AAh

MOVWF EECON2 ; write 0AAh

BSF EECON1, WR ; start erase (CPU stall)

BSF INTCON, GIE ; re-enable interrupts

PIC18F2221/2321/4221/4321 FAMILY

7.5 Writing to Flash Program Memory

The minimum programming block is 4 words or 8 bytes.

Word or byte programming is not supported.

Table writes are used internally to load the holding

registers needed to program the Flash memory. There

are 8 holding registers used by the table writes for

programming.

Since the Table Latch (TABLAT) is only a single byte,

the TBLWT instruction may need to be executed 8 times

for each programming operation. All of the table write

operations will essentially be short writes because only

the holding registers are written. At the end of updating

the 8 holding registers, the EECON1 register must be

written to in order to start the programming operation with

a long write.

The long write is necessary for programming the

internal Flash. Instruction execution is halted while in a

long write cycle. The long write will be terminated by

the internal programming timer.

The EEPROM on-chip timer controls the write time.

The write/erase voltages are generated by an on-chip

charge pump, rated to operate over the voltage range

of the device.

FIGURE 7-5: TABLE WRITES TO FLASH PROGRAM MEMORY

7.5.1 FLASH PROGRAM MEMORY

WRITE SEQUENCE

The sequence of events for programming an internal

program memory location should be:

1. Read 64 bytes into RAM.

2. Update data values in RAM as necessary.

3. Load Table Pointer register with address being

erased.

4. Execute the row erase procedure.

5. Load Table Pointer register with address of first

byte being written.

6. Write the 8 bytes into the holding registers.

7. Set the EECON1 register for the write operation:

• set EEPGD bit to point to program memory;

• clear the CFGS bit to access program memory;

• set WREN to enable byte writes.

8. Disable interrupts.

9. Write 55h to EECON2.

10. Write 0AAh to EECON2.

11. Set the WR bit. This will begin the write cycle.

12. The CPU will stall for duration of the write (about

2 ms using internal timer).

13. Repeat from step 5 seven more times.

14. Re-enable interrupts.

15. Verify the memory (table read).

This procedure will require about 18 ms to update one

row of 64 bytes of memory. An example of the required

code is given in Example 7-3.

Note: The default value of the holding registers on

device Resets and after write operations is

FFh. A write of FFh to a holding register

does not modify that byte. This means that

individual bytes of program memory may be

modified, provided that the modification

does not attempt to change any bit from a

‘0’ to a ‘1’. When modifying individual bytes,

it is not necessary to load all 8 holding

registers before executing a write operation.

TABLAT

TBLPTR = xxxxx7TBLPTR = xxxxx1TBLPTR = xxxxx0

Write Register

TBLPTR = xxxxx2

Program Memory

Holding Register Holding Register Holding Register Holding Register

88 8 8

Note: Before setting the WR bit, the Table

Pointer address needs to be within the

intended address range of the 8 bytes in

the holding register.

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EXAMPLE 7-3: WRITING TO FLASH PROGRAM MEMORY

MOVLW D'64' ; number of bytes in erase block

MOVWF COUNTER

MOVLW BUFFER_ADDR_HIGH ; point to buffer

MOVWF FSR0H

MOVLW BUFFER_ADDR_LOW

MOVWF FSR0L

MOVLW CODE_ADDR_UPPER ; Load TBLPTR with the base

MOVWF TBLPTRU ; address of the memory block

MOVLW CODE_ADDR_HIGH

MOVWF TBLPTRH

MOVLW CODE_ADDR_LOW ; 6 LSB = 0

MOVWF TBLPTRL

READ_BLOCK

TBLRD*+ ; read into TABLAT, and inc

MOVF TABLAT, W ; get data

MOVWF POSTINC0 ; store data and increment FSR0

DECFSZ COUNTER ; done?

BRA READ_BLOCK ; repeat

MODIFY_WORD

MOVLW DATA_ADDR_HIGH ; point to buffer

MOVWF FSR0H

MOVLW DATA_ADDR_LOW

MOVWF FSR0L

MOVLW NEW_DATA_LOW ; update buffer word and increment FSR0

MOVWF POSTINC0

MOVLW NEW_DATA_HIGH ; update buffer word

MOVWF INDF0

ERASE_BLOCK

MOVLW CODE_ADDR_UPPER ; load TBLPTR with the base

MOVWF TBLPTRU ; address of the memory block

MOVLW CODE_ADDR_HIGH

MOVWF TBLPTRH

MOVLW CODE_ADDR_LOW ; 6 LSB = 0

MOVWF TBLPTRL

BCF EECON1, CFGS ; point to PROG/EEPROM memory

BSF EECON1, EEPGD ; point to Flash program memory

BSF EECON1, WREN ; enable write to memory

BSF EECON1, FREE ; enable Row Erase operation

BCF INTCON, GIE ; disable interrupts

MOVLW 55h ; Required sequence

MOVWF EECON2 ; write 55h

MOVLW 0AAh

MOVWF EECON2 ; write AAh

BSF EECON1, WR ; start erase (CPU stall)

NOP

BSF INTCON, GIE ; re-enable interrupts

WRITE_BUFFER_BACK

MOVLW 8 ; number of write buffer groups of 8 bytes

MOVWF COUNTER_HI

MOVLW BUFFER_ADDR_HIGH ; point to buffer

MOVWF FSR0H

MOVLW BUFFER_ADDR_LOW

MOVWF FSR0L

PROGRAM_LOOP

MOVLW 8 ; number of bytes in holding register

MOVWF COUNTER

WRITE_WORD_TO_HREGS

MOVF POSTINC0, W ; get low byte of buffer data and increment FSR0

MOVWF TABLAT ; present data to table latch

TBLWT+* ; short write

; to internal TBLWT holding register, increment

; TBLPTR

DECFSZ COUNTER ; loop until buffers are full

GOTO WRITE_WORD_TO_HREGS

PIC18F2221/2321/4221/4321 FAMILY

EXAMPLE 7-3: WRITING TO FLASH PROGRAM MEMORY (CONTINUED)

7.5.2 WRITE VERIFY

Depending on the application, good programming

practice may dictate that the value written to the

memory should be verified against the original value.

This should be used in applications where excessive

writes can stress bits near the specification limit.

7.5.3 UNEXPECTED TERMINATION OF

WRITE OPERATION

If a write is terminated by an unplanned event, such as

loss of power or an unexpected Reset, the memory

location just programmed should be verified and repro-

grammed if needed. If the write operation is interrupted

by a MCLR Reset or a WDT Time-out Reset during

normal operation, the user can check the WRERR bit

and rewrite the location(s) as needed.

7.5.4 PROTECTION AGAINST

SPURIOUS WRITES

To protect against spurious writes to Flash program

memory, the write initiate sequence must also be

followed. See Section 24.0 “Special Features of the

CPU” for more detail.

7.6 Flash Program Operation During

Code Protection

See Section 24.5 “Program Verification and Code

Protection” for details on code protection of Flash

program memory.

TABLE 7-2: REGISTERS ASSOCIATED WITH PROGRAM FLASH MEMORY

PROGRAM_MEMORY

BCF INTCON, GIE ; disable interrupts

MOVLW 55h ; required sequence

MOVWF EECON2 ; write 55h

MOVLW 0AAh

MOVWF EECON2 ; write AAh

BSF EECON1, WR ; start program (CPU stall)

NOP

BSF INTCON, GIE ; re-enable interrupts

DECFSZ COUNTER_HI ; loop until done

GOTO PROGRAM_LOOP

BCF EECON1, WREN ; disable write to memory

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values on

page

TBLPTRU —— bit 21 Program Memory Table Pointer Upper Byte (TBLPTR<20:16>) 55

TBPLTRH Program Memory Table Pointer High Byte (TBLPTR<15:8>) 55

TBLPTRL Program Memory Table Pointer Low Byte (TBLPTR<7:0>) 55

TABLAT Program Memory Table Latch 55

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

EECON2 EEPROM Control Register 2 (not a physical register) 57

EECON1 EEPGD CFGS — FREE WRERR WREN WR RD 57

IPR2 OSCFIP CMIP — EEIP BCLIP HLVDIP TMR3IP CCP2IP 58

PIR2 OSCFIF CMIF — EEIF BCLIF HLVDIF TMR3IF CCP2IF 58

PIE2 OSCFIE CMIE — EEIE BCLIE HLVDIE TMR3IE CCP2IE 58

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used during Flash/EEPROM access.

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

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8.0 DATA EEPROM MEMORY

The data EEPROM is a nonvolatile memory array,

separate from the data RAM and program memory, that

is used for long-term storage of program data. It is not

directly mapped in either the register file or program

memory space but is indirectly addressed through the

Special Function Registers (SFRs). The EEPROM is

readable and writable during normal operation over the

entire VDD range.

Four SFRs are used to read and write to the data

EEPROM as well as the program memory. They are:

• EECON1

• EECON2

• EEDATA

• EEADR

The data EEPROM allows byte read and write. When

interfacing to the data memory block, EEDATA holds

the 8-bit data for read/write and the EEADR register

holds the address of the EEPROM location being

accessed.

The EEPROM data memory is rated for high erase/write

cycle endurance. A byte write automatically erases the

location and writes the new data (erase-before-write).

The write time is controlled by an on-chip timer. It will

vary with voltage and temperature as well as from chip

to chip. Please refer to parameter D122 (Table 27-1 in

Section 27.0 “Electrical Characteristics”) for exact

limits.

8.1 EECON1 and EECON2 Registers

Access to the data EEPROM is controlled by two

registers: EECON1 and EECON2. These are the same

registers which control access to the program memory

and are used in a similar manner for the data

EEPROM.

The EECON1 register (Register 8-1) is the control

bit EEPGD determines if the access will be to program

or data EEPROM memory. When clear, operations will

access the data EEPROM memory. When set, program

memory is accessed.

Control bit CFGS determines if the access will be to the

Configuration registers or to program memory/data

EEPROM memory. When set, subsequent operations

access Configuration registers. When CFGS is clear,

the EEPGD bit selects either program Flash or data

EEPROM memory.

The WREN bit, when set, will allow a write operation.

On power-up, the WREN bit is clear. The WRERR bit is

set in hardware when the WREN bit is set and cleared

when the internal programming timer expires and the

write operation is complete.

The WR control bit initiates write operations. The bit

cannot be cleared, only set, in software; it is cleared in

hardware at the completion of the write operation.

Control bits, RD and WR, start read and erase/write

operations, respectively. These bits are set by firmware

and cleared by hardware at the completion of the

operation.

The RD bit cannot be set when accessing program

memory (EEPGD = 1). Program memory is read using

table read instructions. See Section 7.1 “Table Reads

and Table Writes” regarding table reads.

The EECON2 register is not a physical register. It is

used exclusively in the memory write and erase

sequences. Reading EECON2 will read all ‘0’s.

Note: During normal operation, the WRERR bit

is read as ‘1’. This can indicate that a write

operation was prematurely terminated by

a Reset, or a write operation was

attempted improperly.

Note: The EEIF interrupt flag bit (PIR2<4>) is set

when the write is complete. It must be

cleared in software.

PIC18F2221/2321/4221/4321 FAMILY

R/W-x R/W-x U-0 R/W-0 R/W-x R/W-0 R/S-0 R/S-0

EEPGD CFGS — FREE WRERR WREN WR RD

bit 7 bit 0

bit 7 EEPGD: Flash Program or Data EEPROM Memory Select bit

1 = Access Flash program memory

0 = Access data EEPROM memory

bit 6 CFGS: Flash Program/Data EEPROM or Configuration Select bit

1 = Access Configuration registers

0 = Access Flash program or data EEPROM memory

bit 5 Unimplemented: Read as ‘0’

bit 4 FREE: Flash Row Erase Enable bit

1 = Erase the program memory row addressed by TBLPTR on the next WR command (cleared

by completion of erase operation)

0 = Perform write only

bit 3 WRERR: Flash Program/Data EEPROM Error Flag bit

1 = A write operation is prematurely terminated (any Reset during self-timed programming in

normal operation, or an improper write attempt)

0 = The write operation completed

Note: When a WRERR occurs, the EEPGD and CFGS bits are not cleared.

This allows tracing of the error condition.

bit 2 WREN: Flash Program/Data EEPROM Write Enable bit

1 = Allows write cycles to Flash program/data EEPROM

0 = Inhibits write cycles to Flash program/data EEPROM

bit 1 WR: Write Control bit

1 = Initiates a data EEPROM erase/write cycle or a program memory erase cycle or write cycle

(The operation is self-timed and the bit is cleared by hardware once write is complete.

The WR bit can only be set (not cleared) in software.)

0 = Write cycle to the EEPROM is complete

bit 0 RD: Read Control bit

1 = Initiates an EEPROM read

(Read takes one cycle. RD is cleared in hardware. The RD bit can only be set (not cleared)

in software. RD bit cannot be set when EEPGD = 1 or CFGS = 1.)

0 = Does not initiate an EEPROM read

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

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8.2 Reading the Data EEPROM

Memory

To read a data memory location, the user must write the

address to the EEADR register, clear the EEPGD

control bit (EECON1<7>) and then set control bit, RD

(EECON1<0>). The data is available on the very next

instruction cycle; therefore, the EEDATA register can

be read by the next instruction. EEDATA will hold this

value until another read operation, or until it is written to

by the user (during a write operation).

The basic process is shown in Example 8-1.

8.3 Writing to the Data EEPROM

Memory

To write an EEPROM data location, the address must

first be written to the EEADR register and the data

written to the EEDATA register. The sequence in

Example 8-2 must be followed to initiate the write cycle.

The write will not begin if this sequence is not exactly

followed (write 55h to EECON2, write 0AAh to

EECON2, then set WR bit) for each byte. It is strongly

recommended that interrupts be disabled during this

code segment.

Additionally, the WREN bit in EECON1 must be set to

enable writes. This mechanism prevents accidental

writes to data EEPROM due to unexpected code

execution (i.e., runaway programs). The WREN bit

should be kept clear at all times, except when updating

the EEPROM. The WREN bit is not cleared by

hardware.

After a write sequence has been initiated, EECON1,

EEADR and EEDATA cannot be modified. The WR bit

will be inhibited from being set unless the WREN bit is

set. The WREN bit must be set on a previous instruc-

tion. Both WR and WREN cannot be set with the same

instruction.

At the completion of the write cycle, the WR bit is

cleared in hardware and the EEPROM Interrupt Flag

bit, EEIF, is set. The user may either enable this

interrupt, or poll this bit. EEIF must be cleared by

software.

8.4 Write Verify

Depending on the application, good programming

practice may dictate that the value written to the mem-

ory should be verified against the original value. This

should be used in applications where excessive writes

can stress bits near the specification limit.

EXAMPLE 8-1: DATA EEPROM READ

EXAMPLE 8-2: DATA EEPROM WRITE

MOVLW DATA_EE_ADDR ;

MOVWF EEADR ; Data Memory Address to read

BCF EECON1, EEPGD ; Point to DATA memory

BCF EECON1, CFGS ; Access EEPROM

BSF EECON1, RD ; EEPROM Read

MOVF EEDATA, W ; W = EEDATA

MOVLW DATA_EE_ADDR ;

MOVWF EEADR ; Data Memory Address to write

MOVLW DATA_EE_DATA ;

MOVWF EEDATA ; Data Memory Value to write

BCF EECON1, EEPGD ; Point to DATA memory

BCF EECON1, CFGS ; Access EEPROM

BSF EECON1, WREN ; Enable writes

BCF INTCON, GIE ; Disable Interrupts

MOVLW 55h ;

Required MOVWF EECON2 ; Write 55h

Sequence MOVLW 0AAh ;

MOVWF EECON2 ; Write 0AAh

BSF EECON1, WR ; Set WR bit to begin write

BTFSC EECON1, WR ; Wait for write to complete

GOTO $-2

BSF INTCON, GIE ; Enable Interrupts

; User code execution

BCF EECON1, WREN ; Disable writes on write complete (EEIF set)

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8.5 Operation During Code-Protect

Data EEPROM memory has its own code-protect bits in

Configuration Words. External read and write

operations are disabled if code protection is enabled.

The microcontroller itself can both read and write to the

internal data EEPROM, regardless of the state of the

code-protect Configuration bit. Refer to Section 24.0

“Special Features of the CPU” for additional

information.

8.6 Protection Against Spurious Write

To protect against spurious EEPROM writes, various

mechanisms have been implemented. On power-up,

the WREN bit is cleared. In addition, writes to the

EEPROM are blocked during the Power-up Timer

period (TPWRT, parameter 33).

The write initiate sequence and the WREN bit together

help prevent an accidental write during Brown-out

Reset, power glitch or software malfunction.

8.7 Using the Data EEPROM

The data EEPROM is a high-endurance, byte

addressable array that has been optimized for the

storage of frequently changing data. Such data is

typically updated at least one time within the number of

writes defined by specification, D124. If any location

storing data is not written at least this often, the data

EEPROM array must be refreshed. For this reason,

values that change infrequently, or not at all, should be

stored in Flash program memory.

A simple data EEPROM refresh routine is shown in

Example 8-3.

EXAMPLE 8-3: DATA EEPROM REFRESH ROUTINE

Note: If data EEPROM is only used to store con-

stants and/or data that changes often, an

array refresh is likely not required. See

specification, D124.

CLRF EEADR ; Start at address 0

BCF EECON1, CFGS ; Set for memory

BCF EECON1, EEPGD ; Set for Data EEPROM

BCF INTCON, GIE ; Disable interrupts

BSF EECON1, WREN ; Enable writes

LOOP ; Loop to refresh array

BSF EECON1, RD ; Read current address

MOVLW 55h ;

MOVWF EECON2 ; Write 55h

MOVLW 0AAh ;

MOVWF EECON2 ; Write 0AAh

BSF EECON1, WR ; Set WR bit to begin write

BTFSC EECON1, WR ; Wait for write to complete

BRA $-2

INCFSZ EEADR, F ; Increment address

BRA LOOP ; Not zero, do it again

BCF EECON1, WREN ; Disable writes

BSF INTCON, GIE ; Enable interrupts

PIC18F2221/2321/4221/4321 FAMILY

TABLE 8-1: REGISTERS ASSOCIATED WITH DATA EEPROM MEMORY

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

EEADR EEPROM Address Register 57

EEDATA EEPROM Data Register 57

EECON2 EEPROM Control Register 2 (not a physical register) 57

EECON1 EEPGD CFGS — FREE WRERR WREN WR RD 57

IPR2 OSCFIP CMIP — EEIP BCLIP HLVDIP TMR3IP CCP2IP 58

PIR2 OSCFIF CMIF — EEIF BCLIF HLVDIF TMR3IF CCP2IF 58

PIE2 OSCFIE CMIE — EEIE BCLIE HLVDIE TMR3IE CCP2IE 58

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used during Flash/EEPROM access.

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

9.0 8 x 8 HARDWARE MULTIPLIER

9.1 Introduction

All PIC18 devices include an 8 x 8 hardware multiplier

as part of the ALU. The multiplier performs an unsigned

operation and yields a 16-bit result that is stored in the

product register pair, PRODH:PRODL. The multiplier’s

operation does not affect any flags in the STATUS

Making multiplication a hardware operation allows it to

be completed in a single instruction cycle. This has the

advantages of higher computational throughput and

reduced code size for multiplication algorithms and

allows the PIC18 devices to be used in many applica-

tions previously reserved for digital signal processors.

A comparison of various hardware and software

multiply operations, along with the savings in memory

and execution time, is shown in Table 9-1.

9.2 Operation

Example 9-1 shows the instruction sequence for an 8 x 8

unsigned multiplication. Only one instruction is required

when one of the arguments is already loaded in the

WREG register.

Example 9-2 shows the sequence to do an 8 x 8 signed

multiplication. To account for the sign bits of the

arguments, each argument’s Most Significant bit (MSb)

is tested and the appropriate subtractions are done.

EXAMPLE 9-1: 8 x 8 UNSIGNED

MULTIPLY ROUTINE

EXAMPLE 9-2: 8 x 8 SIGNED MULTIPLY

ROUTINE

TABLE 9-1: PERFORMANCE COMPARISON FOR VARIOUS MULTIPLY OPERATIONS

MOVF ARG1, W ;

MULWF ARG2 ; ARG1 * ARG2 ->

; PRODH:PRODL

MOVF ARG1, W

MULWF ARG2 ; ARG1 * ARG2 ->

; PRODH:PRODL

BTFSC ARG2, SB ; Test Sign Bit

SUBWF PRODH, F ; PRODH = PRODH

; - ARG1

MOVF ARG2, W

BTFSC ARG1, SB ; Test Sign Bit

SUBWF PRODH, F ; PRODH = PRODH

; - ARG2

Routine Multiply Method

Program

Memory

(Words)

Cycles

(Max)

Time

@ 40 MHz @ 10 MHz @ 4 MHz

8 x 8 unsigned Without hardware multiply 13 69 6.9 μs27.6 μs69 μs

Hardware multiply 1 1 100 ns 400 ns 1 μs

8 x 8 signed Without hardware multiply 33 91 9.1 μs36.4 μs91 μs

Hardware multiply 6 6 600 ns 2.4 μs6 μs

16 x 16 unsigned Without hardware multiply 21 242 24.2 μs96.8 μs242 μs

Hardware multiply 28 28 2.8 μs 11.2 μs28 μs

16 x 16 signed Without hardware multiply 52 254 25.4 μs 102.6 μs254 μs

Hardware multiply 35 40 4.0 μs16.0 μs40 μs

PIC18F2221/2321/4221/4321 FAMILY

Example 9-3 shows the sequence to do a 16 x 16

unsigned multiplication. Equation 9-1 shows the

algorithm that is used. The 32-bit result is stored in four

registers (RES3:RES0).

EQUATION 9-1: 16 x 16 UNSIGNED

MULTIPLICATION

ALGORITHM

EXAMPLE 9-3: 16 x 16 UNSIGNED

MULTIPLY ROUTINE

Example 9-4 shows the sequence to do a 16 x 16

signed multiply. Equation 9-2 shows the algorithm

used. The 32-bit result is stored in four registers

(RES3:RES0). To account for the sign bits of the

arguments, the MSb for each argument pair is tested

and the appropriate subtractions are done.

EQUATION 9-2: 16 x 16 SIGNED

MULTIPLICATION

ALGORITHM

EXAMPLE 9-4: 16 x 16 SIGNED

MULTIPLY ROUTINE

RES3:RES0 = ARG1H:ARG1L • ARG2H:ARG2L

= (ARG1H • ARG2H • 216) +

(ARG1H • ARG2L • 28) +

(ARG1L • ARG2H • 28) +

(ARG1L • ARG2L)

MOVF ARG1L, W

MULWF ARG2L ; ARG1L * ARG2L->

; PRODH:PRODL

MOVFF PRODH, RES1 ;

MOVFF PRODL, RES0 ;

;

MOVF ARG1H, W

MULWF ARG2H ; ARG1H * ARG2H->

; PRODH:PRODL

MOVFF PRODH, RES3 ;

MOVFF PRODL, RES2 ;

;

MOVF ARG1L, W

MULWF ARG2H ; ARG1L * ARG2H->

; PRODH:PRODL

MOVF PRODL, W ;

ADDWF RES1, F ; Add cross

MOVF PRODH, W ; products

ADDWFC RES2, F ;

CLRF WREG ;

ADDWFC RES3, F ;

;

MOVF ARG1H, W ;

MULWF ARG2L ; ARG1H * ARG2L->

; PRODH:PRODL

MOVF PRODL, W ;

ADDWF RES1, F ; Add cross

MOVF PRODH, W ; products

ADDWFC RES2, F ;

CLRF WREG ;

ADDWFC RES3, F ;

RES3:RES0 = ARG1H:ARG1L • ARG2H:ARG2L

= (ARG1H • ARG2H • 216) +

(ARG1H • ARG2L • 28) +

(ARG1L • ARG2H • 28) +

(ARG1L • ARG2L) +

(-1 • ARG2H<7> • ARG1H:ARG1L • 216) +

(-1 • ARG1H<7> • ARG2H:ARG2L • 216)

MOVF ARG1L, W

MULWF ARG2L ; ARG1L * ARG2L ->

; PRODH:PRODL

MOVFF PRODH, RES1 ;

MOVFF PRODL, RES0 ;

;

MOVF ARG1H, W

MULWF ARG2H ; ARG1H * ARG2H ->

; PRODH:PRODL

MOVFF PRODH, RES3 ;

MOVFF PRODL, RES2 ;

;

MOVF ARG1L, W

MULWF ARG2H ; ARG1L * ARG2H ->

; PRODH:PRODL

MOVF PRODL, W ;

ADDWF RES1, F ; Add cross

MOVF PRODH, W ; products

ADDWFC RES2, F ;

CLRF WREG ;

ADDWFC RES3, F ;

;

MOVF ARG1H, W ;

MULWF ARG2L ; ARG1H * ARG2L ->

; PRODH:PRODL

MOVF PRODL, W ;

ADDWF RES1, F ; Add cross

MOVF PRODH, W ; products

ADDWFC RES2, F ;

CLRF WREG ;

ADDWFC RES3, F ;

;

BTFSS ARG2H, 7 ; ARG2H:ARG2L neg?

BRA SIGN_ARG1 ; no, check ARG1

MOVF ARG1L, W ;

SUBWF RES2 ;

MOVF ARG1H, W ;

SUBWFB RES3

;

SIGN_ARG1

BTFSS ARG1H, 7 ; ARG1H:ARG1L neg?

BRA CONT_CODE ; no, done

MOVF ARG2L, W ;

SUBWF RES2 ;

MOVF ARG2H, W ;

SUBWFB RES3

;

CONT_CODE

PIC18F2221/2321/4221/4321 FAMILY

10.0 INTERRUPTS

The PIC18F2221/2321/4221/4321 family devices have

multiple interrupt sources and an interrupt priority

feature that allows most interrupt sources to be

assigned a high-priority level or a low-priority level. The

high-priority interrupt vector is at 0008h and the low-

priority interrupt vector is at 0018h. High-priority

interrupt events will interrupt any low-priority interrupts

that may be in progress.

There are ten registers which are used to control

interrupt operation. These registers are:

• RCON

•INTCON

• INTCON2

• INTCON3

• PIR1, PIR2

• PIE1, PIE2

• IPR1, IPR2

It is recommended that the Microchip header files

supplied with MPLAB® IDE be used for the symbolic bit

names in these registers. This allows the assembler/

compiler to automatically take care of the placement of

these bits within the specified register.

In general, interrupt sources have three bits to control

their operation. They are:

•Flag bit to indicate that an interrupt event

occurred

•Enable bit that allows program execution to

branch to the interrupt vector address when the

flag bit is set

•Priority bit to select high priority or low priority

The interrupt priority feature is enabled by setting the

IPEN bit (RCON<7>). When interrupt priority is

enabled, there are two bits which enable interrupts

globally. Setting the GIEH bit (INTCON<7>) enables all

interrupts that have the priority bit set (high priority).

Setting the GIEL bit (INTCON<6>) enables all

interrupts that have the priority bit cleared (low priority).

When the interrupt flag, enable bit and appropriate

global interrupt enable bit are set, the interrupt will vec-

tor immediately to address 0008h or 0018h, depending

on the priority bit setting. Individual interrupts can be

disabled through their corresponding enable bits.

When the IPEN bit is cleared (default state), the

interrupt priority feature is disabled and interrupts are

compatible with PIC® mid-range devices. In

Compatibility mode, the interrupt priority bits for each

source have no effect. INTCON<6> is the PEIE bit,

which enables/disables all peripheral interrupt sources.

INTCON<7> is the GIE bit, which enables/disables all

interrupt sources. All interrupts branch to address

0008h in Compatibility mode.

When an interrupt is responded to, the global interrupt

enable bit is cleared to disable further interrupts. If the

IPEN bit is cleared, this is the GIE bit. If interrupt priority

levels are used, this will be either the GIEH or GIEL bit.

High-priority interrupt sources can interrupt a low-

priority interrupt. Low-priority interrupts are not

processed while high-priority interrupts are in progress.

The return address is pushed onto the stack and the

PC is loaded with the interrupt vector address (0008h

or 0018h). Once in the Interrupt Service Routine, the

source(s) of the interrupt can be determined by polling

the interrupt flag bits. The interrupt flag bits must be

cleared in software before re-enabling interrupts to

avoid recursive interrupts.

The “return from interrupt” instruction, RETFIE, exits

the interrupt routine and sets the GIE bit (GIEH or GIEL

if priority levels are used), which re-enables interrupts.

For external interrupt events, such as the INTx pins or

the PORTB input change interrupt, the interrupt latency

will be three to four instruction cycles. The exact

latency is the same for one or two-cycle instructions.

Individual interrupt flag bits are set, regardless of the

status of their corresponding enable bit or the GIE bit.

Note: Do not use the MOVFF instruction to modify

any of the interrupt control registers while

any interrupt is enabled. Doing so may

cause erratic microcontroller behavior.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 10-1: PIC18 INTERRUPT LOGIC

TMR0IE

GIE/GIEH

PEIE/GIEL

Wake-up if in

Interrupt to CPU

Vector to Location

0008h

INT2IF

INT2IE

INT2IP

INT1IF

INT1IE

INT1IP

TMR0IF

TMR0IE

TMR0IP

RBIF

RBIE

RBIP

IPEN

TMR0IF

TMR0IP

INT1IF

INT1IE

INT1IP

INT2IF

INT2IE

INT2IP

RBIF

RBIE

RBIP

INT0IF

INT0IE

PEIE/GIEL

Interrupt to CPU

Vector to Location

IPEN

0018h

SSPIF

SSPIE

SSPIP

SSPIF

SSPIE

SSPIP

ADIF

ADIE

ADIP

RCIF

RCIE

RCIP

Additional Peripheral Interrupts

ADIF

ADIE

ADIP

High-Priority Interrupt Generation

Low-Priority Interrupt Generation

RCIF

RCIE

RCIP

Additional Peripheral Interrupts

Idle or Sleep modes

GIE/GIEH

PIC18F2221/2321/4221/4321 FAMILY

10.1 INTCON Registers

The INTCON registers are readable and writable

registers, which contain various enable, priority and

flag bits.

Note: Interrupt flag bits are set when an interrupt

condition occurs, regardless of the state of

its corresponding enable bit or the global

interrupt enable bit. User software should

ensure the appropriate interrupt flag bits

are clear prior to enabling an interrupt.

This feature allows for software polling.

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-x

GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF

bit 7 bit 0

bit 7 GIE/GIEH: Global Interrupt Enable bit

When IPEN = 0:

1 = Enables all unmasked interrupts

0 = Disables all interrupts

When IPEN = 1:

1 = Enables all high-priority interrupts

0 = Disables all interrupts

bit 6 PEIE/GIEL: Peripheral Interrupt Enable bit

When IPEN = 0:

1 = Enables all unmasked peripheral interrupts

0 = Disables all peripheral interrupts

When IPEN = 1:

1 = Enables all low-priority peripheral interrupts

0 = Disables all low-priority peripheral interrupts

bit 5 TMR0IE: TMR0 Overflow Interrupt Enable bit

1 = Enables the TMR0 overflow interrupt

0 = Disables the TMR0 overflow interrupt

bit 4 INT0IE: INT0 External Interrupt Enable bit

1 = Enables the INT0 external interrupt

0 = Disables the INT0 external interrupt

bit 3 RBIE: RB Port Change Interrupt Enable bit

1 = Enables the RB port change interrupt

0 = Disables the RB port change interrupt

bit 2 TMR0IF: TMR0 Overflow Interrupt Flag bit

1 = TMR0 register has overflowed (must be cleared in software)

0 = TMR0 register did not overflow

bit 1 INT0IF: INT0 External Interrupt Flag bit

1 = The INT0 external interrupt occurred (must be cleared in software)

0 = The INT0 external interrupt did not occur

bit 0 RBIF: RB Port Change Interrupt Flag bit

1 = At least one of the RB<7:4> pins changed state (must be cleared in software)

0 = None of the RB<7:4> pins have changed state

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

R/W-1 R/W-1 R/W-1 R/W-1 U-0 R/W-1 U-0 R/W-1

RBPU INTEDG0 INTEDG1 INTEDG2 —TMR0IP—RBIP

bit 7 bit 0

bit 7 RBPU: PORTB Pull-up Enable bit

1 = All PORTB pull-ups are disabled

0 = PORTB pull-ups are enabled by individual port latch values

bit 6 INTEDG0: External Interrupt 0 Edge Select bit

1 = Interrupt on rising edge

0 = Interrupt on falling edge

bit 5 INTEDG1: External Interrupt 1 Edge Select bit

1 = Interrupt on rising edge

0 = Interrupt on falling edge

bit 4 INTEDG2: External Interrupt 2 Edge Select bit

1 = Interrupt on rising edge

0 = Interrupt on falling edge

bit 3 Unimplemented: Read as ‘0’

bit 2 TMR0IP: TMR0 Overflow Interrupt Priority bit

1 = High priority

0 = Low priority

bit 1 Unimplemented: Read as ‘0’

bit 0 RBIP: RB Port Change Interrupt Priority bit

1 = High priority

0 = Low priority

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

Note: Interrupt flag bits are set when an interrupt condition occurs, regardless of the state

of its corresponding enable bit or the global interrupt enable bit. User software

should ensure the appropriate interrupt flag bits are clear prior to enabling an

interrupt. This feature allows for software polling.

PIC18F2221/2321/4221/4321 FAMILY

R/W-1 R/W-1 U-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0

INT2IP INT1IP —INT2IEINT1IE— INT2IF INT1IF

bit 7 bit 0

bit 7 INT2IP: INT2 External Interrupt Priority bit

1 = High priority

0 = Low priority

bit 6 INT1IP: INT1 External Interrupt Priority bit

1 = High priority

0 = Low priority

bit 5 Unimplemented: Read as ‘0’

bit 4 INT2IE: INT2 External Interrupt Enable bit

1 = Enables the INT2 external interrupt

0 = Disables the INT2 external interrupt

bit 3 INT1IE: INT1 External Interrupt Enable bit

1 = Enables the INT1 external interrupt

0 = Disables the INT1 external interrupt

bit 2 Unimplemented: Read as ‘0’

bit 1 INT2IF: INT2 External Interrupt Flag bit

1 = The INT2 external interrupt occurred (must be cleared in software)

0 = The INT2 external interrupt did not occur

bit 0 INT1IF: INT1 External Interrupt Flag bit

1 = The INT1 external interrupt occurred (must be cleared in software)

0 = The INT1 external interrupt did not occur

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

Note: Interrupt flag bits are set when an interrupt condition occurs, regardless of the state

of its corresponding enable bit or the global interrupt enable bit. User software

should ensure the appropriate interrupt flag bits are clear prior to enabling an

interrupt. This feature allows for software polling.

PIC18F2221/2321/4221/4321 FAMILY

10.2 PIR Registers

The PIR registers contain the individual flag bits for the

peripheral interrupts. Due to the number of peripheral

interrupt sources, there are two Peripheral Interrupt

Request (Flag) registers (PIR1 and PIR2).

Note 1: Interrupt flag bits are set when an interrupt

condition occurs, regardless of the state of

its corresponding enable bit or the Global

Interrupt Enable bit, GIE (INTCON<7>).

2: User software should ensure the appropri-

ate interrupt flag bits are cleared prior to

enabling an interrupt and after servicing

that interrupt.

R/W-0 R/W-0 R-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0

PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF

bit 7 bit 0

bit 7 PSPIF: Parallel Slave Port Read/Write Interrupt Flag bit(1)

1 = A read or a write operation has taken place (must be cleared in software)

0 = No read or write has occurred

Note 1: This bit is unimplemented on 28-pin devices and will read as ‘0’.

bit 6 ADIF: A/D Converter Interrupt Flag bit

1 = An A/D conversion completed (must be cleared in software)

0 = The A/D conversion is not complete

bit 5 RCIF: EUSART Receive Interrupt Flag bit

1 = The EUSART receive buffer, RCREG, is full (cleared when RCREG is read)

0 = The EUSART receive buffer is empty

bit 4 TXIF: EUSART Transmit Interrupt Flag bit

1 = The EUSART transmit buffer, TXREG, is empty (cleared when TXREG is written)

0 = The EUSART transmit buffer is full

bit 3 SSPIF: Master Synchronous Serial Port Interrupt Flag bit

1 = The transmission/reception is complete (must be cleared in software)

0 = Waiting to transmit/receive

bit 2 CCP1IF: CCP1 Interrupt Flag bit

Capture mode:

1 = A TMR1 register capture occurred (must be cleared in software)

0 = No TMR1 register capture occurred

Compare mode:

1 = A TMR1 register compare match occurred (must be cleared in software)

0 = No TMR1 register compare match occurred

PWM mode:

Unused in this mode.

bit 1 TMR2IF: TMR2 to PR2 Match Interrupt Flag bit

1 = TMR2 to PR2 match occurred (must be cleared in software)

0 = No TMR2 to PR2 match occurred

bit 0 TMR1IF: TMR1 Overflow Interrupt Flag bit

1 = TMR1 register overflowed (must be cleared in software)

0 = TMR1 register did not overflow

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

OSCFIF CMIF — EEIF BCLIF HLVDIF TMR3IF CCP2IF

bit 7 bit 0

bit 7 OSCFIF: Oscillator Fail Interrupt Flag bit

1 = Device oscillator failed, clock input has changed to INTOSC (must be cleared in software)

0 = Device clock operating

bit 6 CMIF: Comparator Interrupt Flag bit

1 = Comparator input has changed (must be cleared in software)

0 = Comparator input has not changed

bit 5 Unimplemented: Read as ‘0’

bit 4 EEIF: Data EEPROM/Flash Write Operation Interrupt Flag bit

1 = The write operation is complete (must be cleared in software)

0 = The write operation is not complete or has not been started

bit 3 BCLIF: Bus Collision Interrupt Flag bit

1 = A bus collision occurred (must be cleared in software)

0 = No bus collision occurred

bit 2 HLVDIF: High/Low-Voltage Detect Interrupt Flag bit

1 = A high/low-voltage condition occurred; direction determined by VDIRMAG bit

(HLVDCON<7>)

0 = A high/low-voltage condition has not occurred

bit 1 TMR3IF: TMR3 Overflow Interrupt Flag bit

1 = TMR3 register overflowed (must be cleared in software)

0 = TMR3 register did not overflow

bit 0 CCP2IF: CCP2 Interrupt Flag bit

Capture mode:

1 = A TMR1 register capture occurred (must be cleared in software)

0 = No TMR1 register capture occurred

Compare mode:

1 = A TMR1 register compare match occurred (must be cleared in software)

0 = No TMR1 register compare match occurred

PWM mode:

Unused in this mode.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

10.3 PIE Registers

The PIE registers contain the individual enable bits for

the peripheral interrupts. Due to the number of periph-

eral interrupt sources, there are two Peripheral Interrupt

Enable registers (PIE1 and PIE2). When IPEN = 0, the

PEIE bit must be set to enable any of these peripheral

interrupts.

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE

bit 7 bit 0

bit 7 PSPIE: Parallel Slave Port Read/Write Interrupt Enable bit(1)

1 = Enables the PSP read/write interrupt

0 = Disables the PSP read/write interrupt

Note 1: This bit is unimplemented on 28-pin devices and will read as ‘0’.

bit 6 ADIE: A/D Converter Interrupt Enable bit

1 = Enables the A/D interrupt

0 = Disables the A/D interrupt

bit 5 RCIE: EUSART Receive Interrupt Enable bit

1 = Enables the EUSART receive interrupt

0 = Disables the EUSART receive interrupt

bit 4 TXIE: EUSART Transmit Interrupt Enable bit

1 = Enables the EUSART transmit interrupt

0 = Disables the EUSART transmit interrupt

bit 3 SSPIE: Master Synchronous Serial Port Interrupt Enable bit

1 = Enables the MSSP interrupt

0 = Disables the MSSP interrupt

bit 2 CCP1IE: CCP1 Interrupt Enable bit

1 = Enables the CCP1 interrupt

0 = Disables the CCP1 interrupt

bit 1 TMR2IE: TMR2 to PR2 Match Interrupt Enable bit

1 = Enables the TMR2 to PR2 match interrupt

0 = Disables the TMR2 to PR2 match interrupt

bit 0 TMR1IE: TMR1 Overflow Interrupt Enable bit

1 = Enables the TMR1 overflow interrupt

0 = Disables the TMR1 overflow interrupt

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

OSCFIE CMIE — EEIE BCLIE HLVDIE TMR3IE CCP2IE

bit 7 bit 0

bit 7 OSCFIE: Oscillator Fail Interrupt Enable bit

1 = Enabled

0 =Disabled

bit 6 CMIE: Comparator Interrupt Enable bit

1 = Enabled

0 =Disabled

bit 5 Unimplemented: Read as ‘0’

bit 4 EEIE: Data EEPROM/Flash Write Operation Interrupt Enable bit

1 = Enabled

0 =Disabled

bit 3 BCLIE: Bus Collision Interrupt Enable bit

1 = Enabled

0 =Disabled

bit 2 HLVDIE: High/Low-Voltage Detect Interrupt Enable bit

1 = Enabled

0 =Disabled

bit 1 TMR3IE: TMR3 Overflow Interrupt Enable bit

1 = Enabled

0 =Disabled

bit 0 CCP2IE: CCP2 Interrupt Enable bit

1 = Enabled

0 =Disabled

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

10.4 IPR Registers

The IPR registers contain the individual priority bits for

the peripheral interrupts. Due to the number of periph-

eral interrupt sources, there are two Peripheral Interrupt

Priority registers (IPR1 and IPR2). Using the priority bits

requires that the Interrupt Priority Enable (IPEN) bit be

set.

R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1

PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP

bit 7 bit 0

bit 7 PSPIP: Parallel Slave Port Read/Write Interrupt Priority bit(1)

1 =High priority

0 = Low priority

Note 1: This bit is unimplemented on 28-pin devices and will read as ‘0’.

bit 6 ADIP: A/D Converter Interrupt Priority bit

1 =High priority

0 = Low priority

bit 5 RCIP: EUSART Receive Interrupt Priority bit

1 =High priority

0 = Low priority

bit 4 TXIP: EUSART Transmit Interrupt Priority bit

1 =High priority

0 = Low priority

bit 3 SSPIP: Master Synchronous Serial Port Interrupt Priority bit

1 =High priority

0 = Low priority

bit 2 CCP1IP: CCP1 Interrupt Priority bit

1 =High priority

0 = Low priority

bit 1 TMR2IP: TMR2 to PR2 Match Interrupt Priority bit

1 =High priority

0 = Low priority

bit 0 TMR1IP: TMR1 Overflow Interrupt Priority bit

1 =High priority

0 = Low priority

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

R/W-1 R/W-1 U-0 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1

OSCFIP CMIP — EEIP BCLIP HLVDIP TMR3IP CCP2IP

bit 7 bit 0

bit 7 OSCFIP: Oscillator Fail Interrupt Priority bit

1 =High priority

0 = Low priority

bit 6 CMIP: Comparator Interrupt Priority bit

1 =High priority

0 = Low priority

bit 5 Unimplemented: Read as ‘0’

bit 4 EEIP: Data EEPROM/Flash Write Operation Interrupt Priority bit

1 =High priority

0 = Low priority

bit 3 BCLIP: Bus Collision Interrupt Priority bit

1 =High priority

0 = Low priority

bit 2 HLVDIP: High/Low-Voltage Detect Interrupt Priority bit

1 =High priority

0 = Low priority

bit 1 TMR3IP: TMR3 Overflow Interrupt Priority bit

1 =High priority

0 = Low priority

bit 0 CCP2IP: CCP2 Interrupt Priority bit

1 =High priority

0 = Low priority

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

10.5 RCON Register

The RCON register contains flag bits which are used to

determine the cause of the last Reset or wake-up from

Idle or Sleep modes. RCON also contains the IPEN bit

which enables interrupt priorities.

The operation of the SBOREN bit and the Reset flag

bits is discussed in more detail in Section 5.1 “RCON

R/W-0 R/W-1(1) U-0 R/W-1 R-1 R-1 R/W-0(2) R/W-0

IPEN SBOREN —RITO PD POR BOR

bit 7 bit 0

bit 7 IPEN: Interrupt Priority Enable bit

1 = Enable priority levels on interrupts

0 = Disable priority levels on interrupts (PIC16XXX Compatibility mode)

bit 6 SBOREN: Software BOR Enable bit(1)

For details of bit operation, see Register 5-1.

bit 5 Unimplemented: Read as ‘0’

bit 4 RI: RESET Instruction Flag bit

For details of bit operation, see Register 5-1.

bit 3 TO: Watchdog Time-out Flag bit

For details of bit operation, see Register 5-1.

bit 2 PD: Power-down Detection Flag bit

For details of bit operation, see Register 5-1.

bit 1 POR: Power-on Reset Status bit(2)

For details of bit operation, see Register 5-1.

bit 0 BOR: Brown-out Reset Status bit

For details of bit operation, see Register 5-1.

Note 1: If SBOREN is enabled, its Reset state is ‘1’; otherwise, it is ‘0’.

2: Actual Reset values are determined by device configuration and the nature of the

device Reset. See Register 5-1 for additional information.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

10.6 INTx Pin Interrupts

External interrupts on the RB0/INT0, RB1/INT1 and

RB2/INT2 pins are edge-triggered. If the corresponding

INTEDGx bit in the INTCON2 register is set (= 1), the

interrupt is triggered by a rising edge; if the bit is clear,

the trigger is on the falling edge. When a valid edge

appears on the RBx/INTx pin, the corresponding flag

bit, INTxF, is set. This interrupt can be disabled by

clearing the corresponding enable bit, INTxE. Flag bit,

INTxF, must be cleared in software in the Interrupt

Service Routine before re-enabling the interrupt.

All external interrupts (INT0, INT1 and INT2) can wake-

up the processor from Idle or Sleep modes if bit INTxE

was set prior to going into those modes. If the Global

Interrupt Enable bit, GIE, is set, the processor will

branch to the interrupt vector following wake-up.

Interrupt priority for INT1 and INT2 is determined by

the value contained in the interrupt priority bits,

INT1IP (INTCON3<6>) and INT2IP (INTCON3<7>).

There is no priority bit associated with INT0. It is

always a high-priority interrupt source.

10.7 TMR0 Interrupt

In 8-bit mode (which is the default), an overflow in the

TMR0 register (FFh →00h) will set flag bit, TMR0IF. In

16-bit mode, an overflow in the TMR0H:TMR0L

interrupt can be enabled/disabled by setting/clearing

enable bit, TMR0IE (INTCON<5>). Interrupt priority for

Timer0 is determined by the value contained in the

interrupt priority bit, TMR0IP (INTCON2<2>). See

Section 12.0 “Timer0 Module” for further details on

the Timer0 module.

10.8 PORTB Interrupt-on-Change

An input change on PORTB<7:4> sets flag bit, RBIF

(INTCON<0>). The interrupt can be enabled/disabled

by setting/clearing enable bit, RBIE (INTCON<3>).

Interrupt priority for PORTB interrupt-on-change is

determined by the value contained in the interrupt

priority bit, RBIP (INTCON2<0>).

10.9 Context Saving During Interrupts

During interrupts, the return PC address is saved on

the stack. Additionally, the WREG, STATUS and BSR

registers are saved on the fast return stack. If a fast

return from interrupt is not used (see Section 6.3

“Data Memory Organization”), the user may need to

save the WREG, STATUS and BSR registers on entry

to the Interrupt Service Routine. Depending on the

user’s application, other registers may also need to be

saved. Example 10-1 saves and restores the WREG,

STATUS and BSR registers during an Interrupt Service

Routine.

EXAMPLE 10-1: SAVING STATUS, WREG AND BSR REGISTERS IN RAM

MOVWF W_TEMP ; W_TEMP is in virtual bank

MOVFF STATUS, STATUS_TEMP ; STATUS_TEMP located anywhere

MOVFF BSR, BSR_TEMP ; BSR_TMEP located anywhere

;

; USER ISR CODE

;

MOVFF BSR_TEMP, BSR ; Restore BSR

MOVF W_TEMP, W ; Restore WREG

MOVFF STATUS_TEMP, STATUS ; Restore STATUS

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

11.0 I/O PORTS

Depending on the device selected and features

enabled, there are up to five ports available. Some pins

of the I/O ports are multiplexed with an alternate

function from the peripheral features on the device. In

general, when a peripheral is enabled, that pin may not

be used as a general purpose I/O pin.

Each port has three registers for its operation. These

registers are:

• TRIS register (Data Direction register)

• PORT register (reads the levels on the pins of the

device)

• LAT register (Data Latch register)

The Data Latch (LAT register) is useful for read-modify-

write operations on the value that the I/O pins are

driving.

A simplified model of a generic I/O port, without the

interfaces to other peripherals, is shown in Figure 11-1.

FIGURE 11-1: GENERIC I/O PORT

OPERATION

11.1 PORTA, TRISA and LATA Registers

PORTA is an 8-bit wide, bidirectional port. The corre-

sponding Data Direction register is TRISA. Setting a

TRISA bit (= 1) will make the corresponding PORTA pin

an input (i.e., put the corresponding output driver in a

High-Impedance mode). Clearing a TRISA bit (= 0) will

make the corresponding PORTA pin an output (i.e., put

the contents of the output latch on the selected pin).

Reading the PORTA register reads the status of the

pins, whereas writing to it, will write to the port latch.

The Data Latch (LATA) register is also memory mapped.

Read-modify-write operations on the LATA register read

and write the latched output value for PORTA.

The RA4 pin is multiplexed with the Timer0 module

clock input and one of the comparator outputs to

become the RA4/T0CKI/C1OUT pin. Pins RA6 and

RA7 are multiplexed with the main oscillator pins. They

are enabled as oscillator or I/O pins by the selection of

the main oscillator in the Configuration register (see

Section 24.1 “Configuration Bits” for details). When

they are not used as port pins, RA6 and RA7 and their

associated TRIS and LAT bits are read as ‘0’.

The other PORTA pins are multiplexed with analog

inputs, the analog VREF+ and VREF- inputs and the

comparator voltage reference output. The operation of

pins RA<3:0> and RA5 as A/D converter inputs is

selected by clearing or setting the control bits in the

ADCON1 register (A/D Control Register 1).

Pins RA0 through RA5 may also be used as comparator

inputs or outputs by setting the appropriate bits in the

CMCON register. To use RA<3:0> as digital inputs, it is

also necessary to turn off the comparators.

The RA4/T0CKI/C1OUT pin is a Schmitt Trigger input.

All other PORTA pins have TTL input levels and full

CMOS output drivers.

The TRISA register controls the direction of the PORTA

pins, even when they are being used as analog inputs.

The user must ensure the bits in the TRISA register are

maintained set when using them as analog inputs.

EXAMPLE 11-1: INITIALIZING PORTA

Data

Bus

WR LAT

WR TRIS

RD PORT

Data Latch

TRIS Latch

RD TRIS

Input

Buffer

I/O pin(1)

RD LAT

or PORT

Note 1: I/O pins have diode protection to VDD and VSS.

Note: On a Power-on Reset, RA5 and RA<3:0>

are configured as analog inputs and read

as ‘0’. RA4 is configured as a digital input.

CLRF PORTA ; Initialize PORTA by

; clearing output

; data latches

CLRF LATA ; Alternate method

; to clear output

; data latches

MOVLW 0Fh ; Configure all A/D

MOVWF ADCON1 ; for digital inputs

MOVWF 07h ; Configure comparators

MOVWF CMCON ; for digital input

MOVLW 0CFh ; Value used to

; initialize data

; direction

MOVWF TRISA ; Set RA<7:6,3:0> as inputs

; RA<5:4> as outputs

PIC18F2221/2321/4221/4321 FAMILY

TABLE 11-1: PORTA I/O SUMMARY

Pin Function TRIS

Setting I/O I/O

Type Description

RA0/AN0 RA0 0O DIG LATA<0> data output; not affected by analog input.

1I TTL PORTA<0> data input; disabled when analog input enabled.

AN0 1I ANA A/D Input Channel 0 and Comparator C1- input. Default input

configuration on POR; does not affect digital output.

RA1/AN1 RA1 0O DIG LATA<1> data output; not affected by analog input.

1I TTL PORTA<1> data input; disabled when analog input enabled.

AN1 1I ANA A/D Input Channel 1 and Comparator C2- input. Default input

configuration on POR; does not affect digital output.

RA2/AN2/

VREF-/CVREF

RA2 0O DIG LATA<2> data output; not affected by analog input. Disabled when

CVREF output enabled.

1I TTL PORTA<2> data input. Disabled when analog functions enabled;

disabled when CVREF output enabled.

AN2 1I ANA A/D Input Channel 2 and Comparator C2+ input. Default input

configuration on POR; not affected by analog output.

VREF-1I ANA A/D and comparator voltage reference low input.

CVREF xO ANA Comparator voltage reference output. Enabling this feature disables

digital I/O.

RA3/AN3/VREF+RA30O DIG LATA<3> data output; not affected by analog input.

1I TTL PORTA<3> data input; disabled when analog input enabled.

AN3 1I ANA A/D Input Channel 3 and Comparator C1+ input. Default input

configuration on POR.

VREF+1I ANA A/D and comparator voltage reference high input.

RA4/T0CKI/C1OUT RA4 0O DIG LATA<4> data output.

1I ST PORTA<4> data input; default configuration on POR.

T0CKI 1I ST Timer0 clock input.

C1OUT 0O DIG Comparator 1 output; takes priority over port data.

RA5/AN4/SS/

HLVDIN/C2OUT

RA5 0O DIG LATA<5> data output; not affected by analog input.

1I TTL PORTA<5> data input; disabled when analog input enabled.

AN4 1I ANA A/D Input Channel 4. Default configuration on POR.

SS 1I TTL Slave Select input for MSSP (MSSP module).

HLVDIN 1I ANA High/Low-Voltage Detect external trip point input.

C2OUT 0O DIG Comparator 2 output; takes priority over port data.

OSC2/CLKO/RA6 RA6 0O DIG LATA<6> data output. Enabled in RCIO, INTIO2 and ECIO modes only.

1I TTL PORTA<6> data input. Enabled in RCIO, INTIO2 and ECIO modes only.

OSC2 xO ANA Main oscillator feedback output connection (XT, HS and LP modes).

CLKO xO DIG System cycle clock output (FOSC/4) in RC, INTIO1 and EC Oscillator

modes.

OSC1/CLKI/RA7 RA7 0O DIG LATA<7> data output. Disabled in external oscillator modes.

1I TTL PORTA<7> data input. Disabled in external oscillator modes.

OSC1 xI ANA Main oscillator input connection.

CLKI xI ANA Main clock input connection.

Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;

x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).

PIC18F2221/2321/4221/4321 FAMILY

TABLE 11-2: SUMMARY OF REGISTERS ASSOCIATED WITH PORTA

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

PORTA RA7(1) RA6(1) RA5 RA4 RA3 RA2 RA1 RA0 58

LATA LATA7(1) LATA6(1) PORTA Data Latch Register (Read and Write to Data Latch) 58

TRISA TRISA7(1) TRISA6(1) PORTA Data Direction Register 58

ADCON1 — — VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 57

CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 57

CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTA.

Note 1: RA<7:6> and their associated latch and data direction bits are enabled as I/O pins based on oscillator

configuration; otherwise, they are read as ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

11.2 PORTB, TRISB and LATB

Registers

PORTB is an 8-bit wide, bidirectional port. The

corresponding Data Direction register is TRISB. Setting

a TRISB bit (= 1) will make the corresponding PORTB

pin an input (i.e., put the corresponding output driver in

a High-Impedance mode). Clearing a TRISB bit (= 0)

will make the corresponding PORTB pin an output (i.e.,

put the contents of the output latch on the selected pin).

The Data Latch register (LATB) is also memory

mapped. Read-modify-write operations on the LATB

PORTB.

EXAMPLE 11-2: INITIALIZING PORTB

Each of the PORTB pins has a weak internal pull-up. A

single control bit can turn on all the pull-ups. This is

performed by clearing bit, RBPU (INTCON2<7>). The

weak pull-up is automatically turned off when the port

pin is configured as an output. The pull-ups are

disabled on a Power-on Reset.

Four of the PORTB pins (RB<7:4>) have an interrupt-

on-change feature. Only pins configured as inputs can

cause this interrupt to occur (i.e., any RB<7:4> pin

configured as an output is excluded from the interrupt-

on-change comparison). The input pins (of RB<7:4>)

are compared with the old value latched on the last

read of PORTB. The “mismatch” outputs of RB<7:4>

are ORed together to generate the RB Port Change

Interrupt with Flag bit, RBIF (INTCON<0>).

This interrupt can wake the device from Sleep mode or

any of the Idle modes. The user, in the Interrupt Service

Routine, can clear the interrupt in the following manner:

a) Any read or write of PORTB (except with the

MOVFF (ANY), PORTB instruction).

b) 1 TCY.

c) Clear flag bit, RBIF.

A mismatch condition will continue to set flag bit, RBIF.

Reading PORTB and waiting 1 TCY will end the

mismatch condition and allow flag bit, RBIF, to be

cleared. Also, if the port pin returns to its original state,

the mismatch condition will be cleared.

The interrupt-on-change feature is recommended for

wake-up on key depression operation and operations

where PORTB is only used for the interrupt-on-change

feature. Polling of PORTB is not recommended while

using the interrupt-on-change feature.

RB3 can be configured by the Configuration bit,

CCP2MX, as the alternate peripheral pin for the CCP2

module (CCP2MX = 0).

Note: On a Power-on Reset, RB<4:0> are

configured as analog inputs by default and

read as ‘0’; RB<7:5> are configured as

digital inputs.

By clearing the Configuration bit,

PBADEN, RB<4:0> will alternatively be

configured as digital inputs on POR.

CLRF PORTB ; Initialize PORTB by

; clearing output

; data latches

CLRF LATB ; Alternate method

; to clear output

; data latches

MOVLW 0Fh ; Set RB<4:0> as

MOVWF ADCON1 ; digital I/O pins

; (required if config bit

; PBADEN is set)

MOVLW 0CFh ; Value used to

; initialize data

; direction

MOVWF TRISB ; Set RB<3:0> as inputs

; RB<5:4> as outputs

; RB<7:6> as inputs

PIC18F2221/2321/4221/4321 FAMILY

TABLE 11-3: PORTB I/O SUMMARY

Pin Function TRIS

Setting I/O I/O

Type Description

RB0/INT0/FLT0/

AN12

RB0 0O DIG LATB<0> data output; not affected by analog input.

1I TTL PORTB<0> data input; weak pull-up when RBPU bit is cleared.

Disabled when analog input enabled.(1)

INT0 1I ST External Interrupt 0 input.

FLT0 1I ST Enhanced PWM Fault input (ECCP1 module); enabled in software.

AN12 1I ANA A/D Input Channel 12.(1)

RB1/INT1/AN10 RB1 0O DIG LATB<1> data output; not affected by analog input.

1I TTL PORTB<1> data input; weak pull-up when RBPU bit is cleared.

Disabled when analog input enabled.(1)

INT1 1I ST External Interrupt 1 input.

AN10 1I ANA A/D Input Channel 10.(1)

RB2/INT2/AN8 RB2 0O DIG LATB<2> data output; not affected by analog input.

1I TTL PORTB<2> data input; weak pull-up when RBPU bit is cleared.

Disabled when analog input enabled.(1)

INT2 1I ST External Interrupt 2 input.

AN8 1I ANA A/D Input Channel 8.(1)

RB3/AN9/CCP2 RB3 0O DIG LATB<3> data output; not affected by analog input.

1I TTL PORTB<3> data input; weak pull-up when RBPU bit is cleared.

Disabled when analog input enabled.(1)

AN9 1I ANA A/D Input Channel 9.(1)

CCP2(2) 0O DIG CCP2 compare and PWM output.

1I ST CCP2 capture input.

RB4/KBI0/AN11 RB4 0O DIG LATB<4> data output; not affected by analog input.

1I TTL PORTB<4> data input; weak pull-up when RBPU bit is cleared.

Disabled when analog input enabled.(1)

KBI0 1I TTL Interrupt-on-change pin.

AN11 1I ANA A/D Input Channel 11.(1)

RB5/KBI1/PGM RB5 0O DIG LATB<5> data output.

1I TTL PORTB<5> data input; weak pull-up when RBPU bit is cleared.

KBI1 1I TTL Interrupt-on-change pin.

PGM xI ST Single-Supply Programming mode entry (ICSP™). Enabled by LVP

Configuration bit; all other pin functions disabled.

RB6/KBI2/PGC RB6 0O DIG LATB<6> data output.

1I TTL PORTB<6> data input; weak pull-up when RBPU bit is cleared.

KBI2 1I TTL Interrupt-on-change pin.

PGC xI ST Serial execution (ICSP™) clock input for ICSP and ICD operation.(3)

RB7/KBI3/PGD RB7 0O DIG LATB<7> data output.

1I TTL PORTB<7> data input; weak pull-up when RBPU bit is cleared.

KBI3 1I TTL Interrupt-on-change pin.

PGD xO DIG Serial execution data output for ICSP and ICD operation.(3)

xI ST Serial execution data input for ICSP and ICD operation.(3)

Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;

x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).

Note 1: Configuration on POR is determined by the PBADEN Configuration bit. Pins are configured as analog inputs by default

when PBADEN is set and digital inputs when PBADEN is cleared.

2: Alternate assignment for CCP2 when the CCP2MX Configuration bit is ‘0’. Default assignment is RC1.

3: All other pin functions are disabled when ICSP or ICD are enabled.

PIC18F2221/2321/4221/4321 FAMILY

TABLE 11-4: SUMMARY OF REGISTERS ASSOCIATED WITH PORTB

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 58

LATB PORTB Data Latch Register (Read and Write to Data Latch) 58

TRISB PORTB Data Direction Register 58

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

INTCON2 RBPU INTEDG0 INTEDG1 INTEDG2 —TMR0IP —RBIP55

INTCON3 INT2IP INT1IP —INT2IEINT1IE— INT2IF INT1IF 55

ADCON1 — — VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTB.

PIC18F2221/2321/4221/4321 FAMILY

11.3 PORTC, TRISC and LATC

Registers

PORTC is an 8-bit wide, bidirectional port. The

corresponding Data Direction register is TRISC. Set-

ting a TRISC bit (= 1) will make the corresponding

PORTC pin an input (i.e., put the corresponding output

driver in a High-Impedance mode). Clearing a TRISC

bit (= 0) will make the corresponding PORTC pin an

output (i.e., put the contents of the output latch on the

selected pin).

The Data Latch register (LATC) is also memory

mapped. Read-modify-write operations on the LATC

PORTC.

PORTC is multiplexed with several peripheral functions

(Table 11-5). The pins have Schmitt Trigger input

buffers. RC1 is normally configured by Configuration

bit, CCP2MX, as the default peripheral pin of the CCP2

module (default/erased state, CCP2MX = 1).

When enabling peripheral functions, care should be

taken in defining TRIS bits for each PORTC pin. Some

peripherals override the TRIS bit to make a pin an output,

while other peripherals override the TRIS bit to make a

pin an input. The user should refer to the corresponding

peripheral section for additional information.

The contents of the TRISC register are affected by

peripheral overrides. Reading TRISC always returns

the current contents, even though a peripheral device

may be overriding one or more of the pins.

EXAMPLE 11-3: INITIALIZING PORTC

Note: On a Power-on Reset, these pins are

configured as digital inputs.

CLRF PORTC ; Initialize PORTC by

; clearing output

; data latches

CLRF LATC ; Alternate method

; to clear output

; data latches

MOVLW 0CFh ; Value used to

; initialize data

; direction

MOVWF TRISC ; Set RC<3:0> as inputs

; RC<5:4> as outputs

; RC<7:6> as inputs

PIC18F2221/2321/4221/4321 FAMILY

TABLE 11-5: PORTC I/O SUMMARY

Pin Function TRIS

Setting I/O I/O

Type Description

RC0/T1OSO/

T13CKI

RC0 0O DIG LATC<0> data output.

1I ST PORTC<0> data input.

T1OSO xO ANA Timer1 oscillator output; enabled when Timer1 oscillator enabled.

Disables digital I/O.

T13CKI 1I ST Timer1/Timer3 counter input.

RC1/T1OSI/CCP2 RC1 0O DIG LATC<1> data output.

1I ST PORTC<1> data input.

T1OSI xI ANA Timer1 oscillator input; enabled when Timer1 oscillator enabled.

Disables digital I/O.

CCP2(1) 0O DIG CCP2 compare and PWM output; takes priority over port data.

1I ST CCP2 capture input.

RC2/CCP1/P1A RC2 0O DIG LATC<2> data output.

1I ST PORTC<2> data input.

CCP1 0O DIG CCP1 compare or PWM output; takes priority over port data.

1I ST CCP1 capture input.

P1A(2) 0O DIG ECCP1 Enhanced PWM output, Channel A. May be configured for

tri-state during Enhanced PWM shutdown events. Takes priority over

port data.

RC3/SCK/SCL RC3 0O DIG LATC<3> data output.

1I ST PORTC<3> data input.

SCK 0O DIG SPI clock output (MSSP module); takes priority over port data.

1I ST SPI clock input (MSSP module).

SCL 0ODIGI

2C™ clock output (MSSP module); takes priority over port data.

1II

2C/SMB I2C clock input (MSSP module); input type depends on module setting.

RC4/SDI/SDA RC4 0O DIG LATC<4> data output.

1I ST PORTC<4> data input.

SDI 1I ST SPI data input (MSSP module).

SDA 1ODIGI

2C data output (MSSP module); takes priority over port data.

1II

2C/SMB I2C data input (MSSP module); input type depends on module setting.

RC5/SDO RC5 0O DIG LATC<5> data output.

1I ST PORTC<5> data input.

SDO 0O DIG SPI data output (MSSP module); takes priority over port data.

RC6/TX/CK RC6 0O DIG LATC<6> data output.

1I ST PORTC<6> data input.

TX 1O DIG Asynchronous serial transmit data output (EUSART module);

takes priority over port data. User must configure as output.

CK 1O DIG Synchronous serial clock output (EUSART module); takes priority

over port data.

1I ST Synchronous serial clock input (EUSART module).

RC7/RX/DT RC7 0O DIG LATC<7> data output.

1I ST PORTC<7> data input.

RX 1I ST Asynchronous serial receive data input (EUSART module).

DT 1O DIG Synchronous serial data output (EUSART module); takes priority over

port data.

1I ST Synchronous serial data input (EUSART module). User must

configure as an input.

Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;

I2C/SMB = I2C/SMBus input buffer; x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).

Note 1: Default assignment for CCP2 when the CCP2MX Configuration bit is set. Alternate assignment is RB3.

2: Enhanced PWM output is available only on PIC18F4221/4321 devices.

PIC18F2221/2321/4221/4321 FAMILY

TABLE 11-6: SUMMARY OF REGISTERS ASSOCIATED WITH PORTC

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

PORTC RC7 RC6 RC5 RC4 RC3 RC2 RC1 RC0 58

LATC PORTC Data Latch Register (Read and Write to Data Latch) 58

TRISC PORTC Data Direction Register 58

PIC18F2221/2321/4221/4321 FAMILY

11.4 PORTD, TRISD and LATD

Registers

PORTD is an 8-bit wide, bidirectional port. The

corresponding Data Direction register is TRISD. Set-

ting a TRISD bit (= 1) will make the corresponding

PORTD pin an input (i.e., put the corresponding output

driver in a High-Impedance mode). Clearing a TRISD

bit (= 0) will make the corresponding PORTD pin an

output (i.e., put the contents of the output latch on the

selected pin).

The Data Latch register (LATD) is also memory

mapped. Read-modify-write operations on the LATD

PORTD.

All pins on PORTD are implemented with Schmitt Trigger

input buffers. Each pin is individually configurable as an

input or output.

Three of the PORTD pins are multiplexed with outputs

P1B, P1C and P1D of the Enhanced CCP module. The

operation of these additional PWM output pins is

covered in greater detail in Section 17.0 “Enhanced

Capture/Compare/PWM (ECCP) Module”.

PORTD can also be configured as an 8-bit wide micro-

processor port (Parallel Slave Port) by setting control

bit, PSPMODE (TRISE<4>). In this mode, the input

buffers are TTL. See Section 11.6 “Parallel Slave

Port” for additional information on the Parallel Slave

Port (PSP).

EXAMPLE 11-4: INITIALIZING PORTD

Note: PORTD is only available on 40/44-pin

devices.

Note: On a Power-on Reset, these pins are

configured as digital inputs.

Note: When the Enhanced PWM mode is used

with either dual or quad outputs, the PSP

functions of PORTD are automatically

disabled.

CLRF PORTD ; Initialize PORTD by

; clearing output

; data latches

CLRF LATD ; Alternate method

; to clear output

; data latches

MOVLW 0CFh ; Value used to

; initialize data

; direction

MOVWF TRISD ; Set RD<3:0> as inputs

; RD<5:4> as outputs

; RD<7:6> as inputs

PIC18F2221/2321/4221/4321 FAMILY

TABLE 11-7: PORTD I/O SUMMARY

Pin Function TRIS

Setting I/O I/O

Type Description

RD0/PSP0 RD0 0O DIG LATD<0> data output.

1I ST PORTD<0> data input.

PSP0 xO DIG PSP read data output (LATD<0>); takes priority over port data.

xI TTL PSP write data input.

RD1/PSP1 RD1 0O DIG LATD<1> data output.

1I ST PORTD<1> data input.

PSP1 xO DIG PSP read data output (LATD<1>); takes priority over port data.

xI TTL PSP write data input.

RD2/PSP2 RD2 0O DIG LATD<2> data output.

1I ST PORTD<2> data input.

PSP2 xO DIG PSP read data output (LATD<2>); takes priority over port data.

xI TTL PSP write data input.

RD3/PSP3 RD3 0O DIG LATD<3> data output.

1I ST PORTD<3> data input.

PSP3 xO DIG PSP read data output (LATD<3>); takes priority over port data.

xI TTL PSP write data input.

RD4/PSP4 RD4 0O DIG LATD<4> data output.

1I ST PORTD<4> data input.

PSP4 xO DIG PSP read data output (LATD<4>); takes priority over port data.

xI TTL PSP write data input.

RD5/PSP5/P1B RD5 0O DIG LATD<5> data output.

1I ST PORTD<5> data input.

PSP5 xO DIG PSP read data output (LATD<5>); takes priority over port data.

xI TTL PSP write data input.

P1B 0O DIG ECCP1 Enhanced PWM output, Channel B; takes priority over port and

PSP data. May be configured for tri-state during Enhanced PWM

shutdown events.

RD6/PSP6/P1C RD6 0O DIG LATD<6> data output.

1I ST PORTD<6> data input.

PSP6 xO DIG PSP read data output (LATD<6>); takes priority over port data.

xI TTL PSP write data input.

P1C 0O DIG ECCP1 Enhanced PWM output, channel C; takes priority over port and

PSP data. May be configured for tri-state during Enhanced PWM

shutdown events.

RD7/PSP7/P1D RD7 0O DIG LATD<7> data output.

1I ST PORTD<7> data input.

PSP7 xO DIG PSP read data output (LATD<7>); takes priority over port data.

xI TTL PSP write data input.

P1D 0O DIG ECCP1 Enhanced PWM output, Channel D; takes priority over port

and PSP data. May be configured for tri-state during Enhanced PWM

shutdown events.

Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; x = Don’t care

(TRIS bit does not affect port direction or is overridden for this option).

PIC18F2221/2321/4221/4321 FAMILY

TABLE 11-8: SUMMARY OF REGISTERS ASSOCIATED WITH PORTD

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

PORTD RD7 RD6 RD5 RD4 RD3 RD2 RD1 RD0 58

LATD PORTD Data Latch Register (Read and Write to Data Latch) 58

TRISD PORTD Data Direction Register 58

TRISE IBF OBF IBOV PSPMODE —TRISE2 TRISE1 TRISE0 58

CCP1CON P1M1 P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTD.

PIC18F2221/2321/4221/4321 FAMILY

11.5 PORTE, TRISE and LATE

Registers

Depending on the particular PIC18F2221/2321/4221/

4321 family device selected, PORTE is implemented in

two different ways.

For 40/44-pin devices, PORTE is a 4-bit wide port.

Three pins (RE0/RD/AN5, RE1/WR/AN6 and RE2/CS/

AN7) are individually configurable as inputs or outputs.

These pins have Schmitt Trigger input buffers. When

selected as analog inputs, these pins will read as ‘0’.

The corresponding Data Direction register is TRISE.

Setting a TRISE bit (= 1) will make the corresponding

PORTE pin an input (i.e., put the corresponding output

driver in a High-Impedance mode). Clearing a TRISE

bit (= 0) will make the corresponding PORTE pin an

output (i.e., put the contents of the output latch on the

selected pin).

TRISE controls the direction of the RE pins, even when

they are being used as analog inputs. The user must

make sure to keep the pins configured as inputs when

using them as analog inputs.

The upper four bits of the TRISE register also control

the operation of the Parallel Slave Port. Their operation

is explained in Register 11-1.

The Data Latch register (LATE) is also memory

mapped. Read-modify-write operations on the LATE

PORTE.

The fourth pin of PORTE (MCLR/VPP/RE3) is an input

only pin. Its operation is controlled by the MCLRE Con-

figuration bit. When selected as a port pin (MCLRE = 0),

it functions as a digital input only pin; as such, it does not

have TRIS or LAT bits associated with its operation.

Otherwise, it functions as the device’s Master Clear

input. In either configuration, RE3 also functions as the

programming voltage input during programming.

EXAMPLE 11-5: INITIALIZING PORTE

11.5.1 PORTE IN 28-PIN DEVICES

For 28-pin devices, PORTE is only available when

Master Clear functionality is disabled (MCLRE = 0). In

these cases, PORTE is a single bit, input only port

comprised of RE3 only. The pin operates as previously

described.

Note: On a Power-on Reset, RE<2:0> are

configured as analog inputs.

Note: On a Power-on Reset, RE3 is enabled as

a digital input only if Master Clear

functionality is disabled.

CLRF PORTE ; Initialize PORTE by

; clearing output

; data latches

CLRF LATE ; Alternate method

; to clear output

; data latches

MOVLW 0Fh ; Configure A/D

MOVWF ADCON1 ; for digital inputs

MOVLW 03h ; Value used to

; initialize data

; direction

MOVWF TRISE ; Set RE<0> as inputs

; RE<1> as outputs

; RE<2> as inputs

PIC18F2221/2321/4221/4321 FAMILY

R-0 R-0 R/W-0 R/W-0 U-0 R/W-1 R/W-1 R/W-1

IBF OBF IBOV PSPMODE — TRISE2 TRISE1 TRISE0

bit 7 bit 0

bit 7 IBF: Input Buffer Full Status bit

1 = A word has been received and waiting to be read by the CPU

0 = No word has been received

bit 6 OBF: Output Buffer Full Status bit

1 = The output buffer still holds a previously written word

0 = The output buffer has been read

bit 5 IBOV: Input Buffer Overflow Detect bit (in Microprocessor mode)

1 = A write occurred when a previously input word has not been read (must be cleared in software)

0 = No overflow occurred

bit 4 PSPMODE: Parallel Slave Port Mode Select bit

1 = Parallel Slave Port mode

0 = General Purpose I/O mode

bit 3 Unimplemented: Read as ‘0’

bit 2 TRISE2: RE2 Direction Control bit

1 = Input

0 = Output

bit 1 TRISE1: RE1 Direction Control bit

1 = Input

0 = Output

bit 0 TRISE0: RE0 Direction Control bit

1 = Input

0 = Output

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

TABLE 11-9: PORTE I/O SUMMARY

TABLE 11-10: SUMMARY OF REGISTERS ASSOCIATED WITH PORTE

Pin Function TRIS

Setting I/O I/O

Type Description

RE0/RD/AN5 RE0 0O DIG LATE<0> data output; not affected by analog input.

1I ST PORTE<0> data input; disabled when analog input enabled.

RD 1I TTL PSP read enable input (PSP enabled).

AN5 1I ANA A/D Input Channel 5; default input configuration on POR.

RE1/WR/AN6 RE1 0O DIG LATE<1> data output; not affected by analog input.

1I ST PORTE<1> data input; disabled when analog input enabled.

WR 1I TTL PSP write enable input (PSP enabled).

AN6 1I ANA A/D Input Channel 6; default input configuration on POR.

RE2/CS/AN7 RE2 0O DIG LATE<2> data output; not affected by analog input.

1I ST PORTE<2> data input; disabled when analog input enabled.

CS 1I TTL PSP write enable input (PSP enabled).

AN7 1I ANA A/D Input Channel 7; default input configuration on POR.

MCLR/VPP/RE3(1) MCLR — I ST External Master Clear input; enabled when MCLRE Configuration bit

is set.

VPP — I ANA High-voltage detection; used for ICSP™ mode entry detection. Always

available, regardless of pin mode.

RE3 —(2) I ST PORTE<3> data input; enabled when MCLRE Configuration bit is

clear.

Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;

x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).

Note 1: RE3 is available on both 28-pin and 40/44-pin devices. All other PORTE pins are only implemented on 40/44-pin devices.

2: RE3 does not have a corresponding TRIS bit to control data direction.

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

PORTE — — — —RE3

(1,2) RE2 RE1 RE0 58

LATE(2) — — — — — PORTE Data Latch Register

(Read and Write to Data Latch)

TRISE IBF OBF IBOV PSPMODE — TRISE2 TRISE1 TRISE0 58

ADCON1 — — VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTE.

Note 1: Implemented only when Master Clear functionality is disabled (MCLRE Configuration bit = 0).

2: RE3 is the only PORTE bit implemented on both 28-pin and 40/44-pin devices. All other bits are

implemented only when PORTE is implemented (i.e., 40/44-pin devices).

PIC18F2221/2321/4221/4321 FAMILY

11.6 Parallel Slave Port

In addition to its function as a general I/O port, PORTD

can also operate as an 8-bit wide Parallel Slave Port

(PSP) or microprocessor port. PSP operation is

controlled by the 4 upper bits of the TRISE register

(Register 11-1). Setting control bit, PSPMODE

(TRISE<4>), enables PSP operation as long as the

Enhanced CCP module is not operating in Dual Output

or Quad Output PWM mode. In Slave mode, the port is

asynchronously readable and writable by the external

world.

The PSP can directly interface to an 8-bit micro-

processor data bus. The external microprocessor can

read or write the PORTD latch as an 8-bit latch. Setting

the control bit, PSPMODE, enables the PORTE I/O

pins to become control inputs for the microprocessor

port. When set, port pin RE0 is the RD input, RE1 is the

WR input and RE2 is the CS (Chip Select) input. For

this functionality, the corresponding data direction bits

of the TRISE register (TRISE<2:0>) must be config-

ured as inputs (set). The A/D port configuration bits,

PFCG<3:0> (ADCON1<3:0>), must also be set to a

value in the range of ‘1010’ through ‘1111’.

A write to the PSP occurs when both the CS and WR

lines are first detected low and ends when either are

detected high. The PSPIF and IBF flag bits are both set

when the write ends.

A read from the PSP occurs when both the CS and RD

lines are first detected low. The data in PORTD is read

out and the OBF bit is clear. If the user writes new data

to PORTD to set OBF, the data is immediately read out;

however, the OBF bit is not set.

When either the CS or RD lines are detected high, the

PORTD pins return to the input state and the PSPIF bit

is set. User applications should wait for PSPIF to be set

before servicing the PSP. When this happens, the IBF

and OBF bits can be polled and the appropriate action

taken.

The timing for the control signals in Write and Read

modes is shown in Figure 11-3 and Figure 11-4,

respectively.

FIGURE 11-2: PORTD AND PORTE

BLOCK DIAGRAM

(PARALLEL SLAVE PORT)

Note: The Parallel Slave Port is only available on

40/44-pin devices.

Data Bus

WR LATD RDx pin

RD PORTD

One bit of PORTD

Set Interrupt Flag

PSPIF (PIR1<7>)

Read

Chip Select

Write

TTL

WR PORTD

RD LATD

Data Latch

Note: I/O pins have diode protection to VDD and VSS.

PORTE Pins

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 11-3: PARALLEL SLAVE PORT WRITE WAVEFORMS

FIGURE 11-4: PARALLEL SLAVE PORT READ WAVEFORMS

TABLE 11-11: REGISTERS ASSOCIATED WITH PARALLEL SLAVE PORT

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values on

page

PORTD RD7 RD6 RD5 RD4 RD3 RD2 RD1 RD0 58

LATD PORTD Data Latch Register (Read and Write to Data Latch) 58

TRISD PORTD Data Direction Register 58

PORTE — — — — RE3 RE2 RE1 RE0 58

LATE — — — — — PORTE Data Latch Register

(Read and Write to Data Latch)

TRISE IBF OBF IBOV PSPMODE — TRISE2 TRISE1 TRISE0 58

INTCON GIE/GIEH PEIE/GIEL TMR0IF INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

ADCON1 — — VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Parallel Slave Port.

Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.

Q1 Q2 Q3 Q4

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

IBF

OBF

PSPIF

PORTD<7:0>

Q1 Q2 Q3 Q4

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

IBF

PSPIF

OBF

PORTD<7:0>

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

12.0 TIMER0 MODULE

The Timer0 module incorporates the following features:

• Software selectable operation as a timer or coun-

ter in both 8-bit or 16-bit modes

• Readable and writable registers

• Dedicated 8-bit, software programmable

prescaler

• Selectable clock source (internal or external)

• Edge select for external clock

• Interrupt-on-overflow

The T0CON register (Register 12-1) controls all

aspects of the module’s operation, including the

prescale selection. It is both readable and writable.

A simplified block diagram of the Timer0 module in 8-bit

mode is shown in Figure 12-1. Figure 12-2 shows a

simplified block diagram of the Timer0 module in 16-bit

mode.

R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1

TMR0ON T08BIT T0CS T0SE PSA T0PS2 T0PS1 T0PS0

bit 7 bit 0

bit 7 TMR0ON: Timer0 On/Off Control bit

1 = Enables Timer0

0 = Stops Timer0

bit 6 T08BIT: Timer0 8-Bit/16-Bit Control bit

1 = Timer0 is configured as an 8-bit timer/counter

0 = Timer0 is configured as a 16-bit timer/counter

bit 5 T0CS: Timer0 Clock Source Select bit

1 = Transition on T0CKI pin

0 = Internal instruction cycle clock (CLKO)

bit 4 T0SE: Timer0 Source Edge Select bit

1 = Increment on high-to-low transition on T0CKI pin

0 = Increment on low-to-high transition on T0CKI pin

bit 3 PSA: Timer0 Prescaler Assignment bit

1 = TImer0 prescaler is NOT assigned. Timer0 clock input bypasses prescaler.

0 = Timer0 prescaler is assigned. Timer0 clock input comes from prescaler output.

bit 2-0 T0PS<2:0>: Timer0 Prescaler Select bits

111 = 1:256 Prescale value

110 = 1:128 Prescale value

101 = 1:64 Prescale value

100 = 1:32 Prescale value

011 = 1:16 Prescale value

010 = 1:8 Prescale value

001 = 1:4 Prescale value

000 = 1:2 Prescale value

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

12.1 Timer0 Operation

Timer0 can operate as either a timer or a counter; the

mode is selected with the T0CS bit (T0CON<5>). In

Timer mode (T0CS = 0), the module increments on

every clock by default unless a different prescaler value

is selected (see Section 12.3 “Prescaler”). If the

TMR0 register is written to, the increment is inhibited

for the following two instruction cycles. The user can

work around this by writing an adjusted value to the

TMR0 register.

The Counter mode is selected by setting the T0CS bit

(= 1). In this mode, Timer0 increments either on every

rising or falling edge of pin RA4/T0CKI. The increment-

ing edge is determined by the Timer0 Source Edge

Select bit, T0SE (T0CON<4>); clearing this bit selects

the rising edge. Restrictions on the external clock input

are discussed below.

An external clock source can be used to drive Timer0;

however, it must meet certain requirements to ensure

that the external clock can be synchronized with the

internal phase clock (T

OSC). There is a delay between

synchronization and the onset of incrementing the

timer/counter.

12.2 Timer0 Reads and Writes in

16-Bit Mode

TMR0H is not the actual high byte of Timer0 in 16-bit

mode; it is actually a buffered version of the real high

byte of Timer0 which is not directly readable nor

writable (refer to Figure 12-2). TMR0H is updated with

the contents of the high byte of Timer0 during a read of

TMR0L. This provides the ability to read all 16 bits of

Timer0 without having to verify that the read of the high

and low byte were valid, due to a rollover between

successive reads of the high and low byte.

Similarly, a write to the high byte of Timer0 must also

take place through the TMR0H Buffer register. The high

byte is updated with the contents of TMR0H when a

write occurs to TMR0L. This allows all 16 bits of Timer0

to be updated at once.

FIGURE 12-1: TIMER0 BLOCK DIAGRAM (8-BIT MODE)

FIGURE 12-2: TIMER0 BLOCK DIAGRAM (16-BIT MODE)

Note: Upon Reset, Timer0 is enabled in 8-bit mode with clock input from T0CKI max. prescale.

T0CKI pin

T0SE

T0CS

FOSC/4

Programmable

Prescaler

Sync with

Internal

Clocks

TMR0L

(2 TOSC Delay)

Internal Data Bus

PSA

T0PS<2:0>

Set

TMR0IF

on Overflow

Note: Upon Reset, Timer0 is enabled in 8-bit mode with clock input from T0CKI max. prescale.

T0CKI pin

T0SE

T0CS

FOSC/4

Programmable

Prescaler

Sync with

Internal

Clocks TMR0L

(2 TOSC Delay)

Internal Data Bus

PSA

T0PS<2:0>

Set

TMR0IF

on Overflow

TMR0

TMR0H

High Byte

Read TMR0L

Write TMR0L

PIC18F2221/2321/4221/4321 FAMILY

12.3 Prescaler

An 8-bit counter is available as a prescaler for the Timer0

module. The prescaler is not directly readable or writable;

its value is set by the PSA and T0PS<2:0> bits

(T0CON<3:0>) which determine the prescaler

assignment and prescale ratio.

Clearing the PSA bit assigns the prescaler to the

Timer0 module. When it is assigned, prescale values

from 1:2 through 1:256 in power-of-2 increments are

selectable.

When assigned to the Timer0 module, all instructions

writing to the TMR0 register (e.g., CLRF TMR0, MOVWF

TMR0, BSF TMR0, etc.) clear the prescaler count.

12.3.1 SWITCHING PRESCALER

ASSIGNMENT

The prescaler assignment is fully under software

control and can be changed “on-the-fly” during program

execution.

12.4 Timer0 Interrupt

The TMR0 interrupt is generated when the TMR0

from FFFFh to 0000h in 16-bit mode. This overflow sets

the TMR0IF flag bit. The interrupt can be masked by

clearing the TMR0IE bit (INTCON<5>). Before re-

enabling the interrupt, the TMR0IF bit must be cleared

in software by the Interrupt Service Routine.

Since Timer0 is shut down in Sleep mode, the TMR0

interrupt cannot awaken the processor from Sleep.

TABLE 12-1: REGISTERS ASSOCIATED WITH TIMER0

Note: Writing to TMR0 when the prescaler is

assigned to Timer0 will clear the prescaler

count but will not change the prescaler

assignment.

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

TMR0L Timer0 Register Low Byte 56

TMR0H Timer0 Register High Byte 56

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

T0CON TMR0ON T08BIT T0CS T0SE PSA T0PS2 T0PS1 T0PS0 56

TRISA RA7(1) RA6(1) RA5 RA4 RA3 RA2 RA1 RA0 58

Legend: Shaded cells are not used by Timer0.

Note 1: PORTA<7:6> and their direction bits are individually configured as port pins based on various primary

oscillator modes. When disabled, these bits read as ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

13.0 TIMER1 MODULE

The Timer1 timer/counter module incorporates these

features:

• Software selectable operation as a 16-bit timer or

counter

• Readable and writable 8-bit registers (TMR1H

and TMR1L)

• Selectable clock source (internal or external) with

device clock or Timer1 oscillator internal options

• Interrupt-on-overflow

• Reset on CCP Special Event Trigger

• Device clock status flag (T1RUN)

A simplified block diagram of the Timer1 module is

shown in Figure 13-1. A block diagram of the module’s

operation in Read/Write mode is shown in Figure 13-2.

The module incorporates its own low-power oscillator

to provide an additional clocking option. The Timer1

oscillator can also be used as a low-power clock source

for the microcontroller in power-managed operation.

Timer1 can also be used to provide Real-Time Clock

(RTC) functionality to applications with only a minimal

addition of external components and code overhead.

Timer1 is controlled through the T1CON Control

Oscillator Enable bit (T1OSCEN). Timer1 can be

enabled or disabled by setting or clearing control bit,

TMR1ON (T1CON<0>).

R/W-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON

bit 7 bit 0

bit 7 RD16: 16-Bit Read/Write Mode Enable bit

1 = Enables register read/write of TImer1 in one 16-bit operation

0 = Enables register read/write of Timer1 in two 8-bit operations

bit 6 T1RUN: Timer1 System Clock Status bit

1 = Device clock is derived from Timer1 oscillator

0 = Device clock is derived from another source

bit 5-4 T1CKPS<1:0>: Timer1 Input Clock Prescale Select bits

11 = 1:8 Prescale value

10 = 1:4 Prescale value

01 = 1:2 Prescale value

00 = 1:1 Prescale value

bit 3 T1OSCEN: Timer1 Oscillator Enable bit

1 = Timer1 oscillator is enabled

0 = Timer1 oscillator is shut off

The oscillator inverter and feedback resistor are turned off to eliminate power drain.

bit 2 T1SYNC: Timer1 External Clock Input Synchronization Select bit

When TMR1CS = 1:

1 = Do not synchronize external clock input

0 = Synchronize external clock input

When TMR1CS = 0:

This bit is ignored. Timer1 uses the internal clock when TMR1CS = 0.

bit 1 TMR1CS: Timer1 Clock Source Select bit

1 = External clock from pin RC0/T1OSO/T13CKI (on the rising edge)

0 = Internal clock (FOSC/4)

bit 0 TMR1ON: Timer1 On bit

1 = Enables Timer1

0 = Stops Timer1

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

13.1 Timer1 Operation

Timer1 can operate in one of these modes:

•Timer

• Synchronous Counter

• Asynchronous Counter

The operating mode is determined by the clock select

bit, TMR1CS (T1CON<1>). When TMR1CS is cleared

(= 0), Timer1 increments on every internal instruction

cycle (Fosc/4). When the bit is set, Timer1 increments

on every rising edge of the Timer1 external clock input

or the Timer1 oscillator, if enabled.

When Timer1 is enabled, the RC1/T1OSI and RC0/

T1OSO/T13CKI pins become inputs. This means the

values of TRISC<1:0> are ignored and the pins are

read as ‘0’.

FIGURE 13-1: TIMER1 BLOCK DIAGRAM

FIGURE 13-2: TIMER1 BLOCK DIAGRAM (16-BIT READ/WRITE MODE)

T1SYNC

TMR1CS

T1CKPS<1:0>

Peripheral Clock

T1OSCEN(1)

FOSC/4

Internal

Clock

On/Off

Prescaler

1, 2, 4, 8

Synchronize

Detect

T1OSO/T13CKI

T1OSI

TMR1ON

TMR1L Set

TMR1IF

on Overflow

TMR1

High Byte

Clear TMR1

(CCP Special Event Trigger)

Timer1 Oscillator

Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.

On/Off

Timer1

Timer1 Clock Input

T1SYNC

TMR1CS

T1CKPS<1:0>

Peripheral Clock

T1OSCEN(1)

FOSC/4

Internal

Clock

Prescaler

1, 2, 4, 8

Synchronize

Detect

T1OSO/T13CKI

T1OSI

Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.

TMR1L

Internal Data Bus

Set

TMR1IF

on Overflow

TMR1

TMR1H

High Byte

Read TMR1L

Write TMR1L

TMR1ON

Clear TMR1

(CCP Special Event Trigger)

Timer1 Oscillator

On/Off

Timer1

Timer1 Clock Input

PIC18F2221/2321/4221/4321 FAMILY

13.2 Timer1 16-Bit Read/Write Mode

Timer1 can be configured for 16-bit reads and writes

(see Figure 13-2). When the RD16 control bit

(T1CON<7>) is set, the address for TMR1H is mapped

to a buffer register for the high byte of Timer1. A read

from TMR1L will load the contents of the high byte of

Timer1 into the Timer1 high byte buffer. This provides

the user with the ability to accurately read all 16 bits of

Timer1 without having to determine whether a read of

the high byte, followed by a read of the low byte, has

become invalid due to a rollover between reads.

A write to the high byte of Timer1 must also take place

through the TMR1H Buffer register. The Timer1 high

byte is updated with the contents of TMR1H when a

write occurs to TMR1L. This allows a user to write all

16 bits to both the high and low bytes of Timer1 at once.

The high byte of Timer1 is not directly readable or

writable in this mode. All reads and writes must take

place through the Timer1 High Byte Buffer register.

Writes to TMR1H do not clear the Timer1 prescaler.

The prescaler is only cleared on writes to TMR1L.

13.3 Timer1 Oscillator

An on-chip crystal oscillator circuit is incorporated

between pins T1OSI (input) and T1OSO (amplifier

output). It is enabled by setting the Timer1 Oscillator

Enable bit, T1OSCEN (T1CON<3>). The oscillator is a

low-power circuit rated for 32 kHz crystals. It will

continue to run during all power-managed modes. The

circuit for a typical LP oscillator is shown in Figure 13-3.

Table 13-1 shows the capacitor selection for the Timer1

oscillator.

The user must provide a software time delay to ensure

proper start-up of the Timer1 oscillator.

FIGURE 13-3: EXTERNAL COMPONENTS

FOR THE TIMER1

LP OSCILLATOR

TABLE 13-1: CAPACITOR SELECTION FOR

THE TIMER OSCILLATOR

13.3.1 USING TIMER1 AS A

CLOCK SOURCE

The Timer1 oscillator is also available as a clock source

in power-managed modes. By setting the clock select

bits, SCS<1:0> (OSCCON<1:0>), to ‘01’, the device

switches to SEC_RUN mode; both the CPU and

peripherals are clocked from the Timer1 oscillator. If the

IDLEN bit (OSCCON<7>) is cleared and a SLEEP

instruction is executed, the device enters SEC_IDLE

mode. Additional details are available in Section 4.0

“Power-Managed Modes”.

Whenever the Timer1 oscillator is providing the clock

source, the Timer1 system clock status flag, T1RUN

(T1CON<6>), is set. This can be used to determine the

controller’s current clocking mode. It can also indicate

the clock source being currently used by the Fail-Safe

Clock Monitor. If the Clock Monitor is enabled and the

Timer1 oscillator fails while providing the clock, polling

the T1RUN bit will indicate whether the clock is being

provided by the Timer1 oscillator or another source.

13.3.2 LOW-POWER TIMER1 OPTION

The Timer1 oscillator can operate at two distinct levels

of power consumption based on device configuration.

When the LPT1OSC Configuration bit is set, the Timer1

oscillator operates in a low-power mode. When

LPT1OSC is not set, Timer1 operates at a higher power

level. Power consumption for a particular mode is

relatively constant, regardless of the device’s operating

mode. The default Timer1 configuration is the higher

power mode.

As the low-power Timer1 mode tends to be more

sensitive to interference, high noise environments may

cause some oscillator instability. The low-power option is,

therefore, best suited for low noise applications where

power conservation is an important design consideration.

Note: See the Notes with Table 13-1 for additional

information about capacitor selection.

XTAL

PIC18FXXXX

T1OSI

T1OSO

32.768 kHz

27 pF

Osc Type Freq C1 C2

LP 32 kHz 27 pF(1) 27 pF(1)

Note 1: Microchip suggests these values as a

starting point in validating the oscillator

circuit.

2: Higher capacitance increases the stability

of the oscillator but also increases the

start-up time.

3: Since each resonator/crystal has its own

characteristics, the user should consult

the resonator/crystal manufacturer for

appropriate values of external

components.

4: Capacitor values are for design guidance

only.

PIC18F2221/2321/4221/4321 FAMILY

13.3.3 TIMER1 OSCILLATOR LAYOUT

CONSIDERATIONS

The Timer1 oscillator circuit draws very little power

during operation. Due to the low-power nature of the

oscillator, it may also be sensitive to rapidly changing

signals in close proximity.

The oscillator circuit, shown in Figure 13-3, should be

located as close as possible to the microcontroller.

There should be no circuits passing within the oscillator

circuit boundaries other than VSS or VDD.

If a high-speed circuit must be located near the

oscillator (such as the CCP1 pin in Output Compare or

PWM mode, or the primary oscillator using the OSC2

pin), a grounded guard ring around the oscillator circuit,

as shown in Figure 13-4, may be helpful when used on

a single-sided PCB or in addition to a ground plane.

FIGURE 13-4: OSCILLATOR CIRCUIT

WITH GROUNDED

GUARD RING

13.4 Timer1 Interrupt

The TMR1 register pair (TMR1H:TMR1L) increments

from 0000h to FFFFh and rolls over to 0000h. The

Timer1 interrupt, if enabled, is generated on overflow

which is latched in interrupt flag bit, TMR1IF

(PIR1<0>). This interrupt can be enabled or disabled

by setting or clearing the Timer1 Interrupt Enable bit,

TMR1IE (PIE1<0>).

13.5 Resetting Timer1 Using the CCP

Special Event Trigger

If either of the CCP modules is configured to use

Timer1 and generate a Special Event Trigger in Com-

pare mode (CCP1M<3:0> or CCP2M<3:0> = 1011),

this signal will reset Timer1. The trigger from CCP2 will

also start an A/D conversion if the A/D module is

enabled (see Section 16.3.4 “Special Event Trigger”

for more information).

The module must be configured as either a timer or a

synchronous counter to take advantage of this feature.

When used this way, the CCPRH:CCPRL register pair

effectively becomes a period register for Timer1.

If Timer1 is running in Asynchronous Counter mode,

this Reset operation may not work.

In the event that a write to Timer1 coincides with a

Special Event Trigger, the write operation will take

precedence.

13.6 Using Timer1 as a Real-Time Clock

Adding an external LP oscillator to Timer1 (such as the

one described in Section 13.3 “Timer1 Oscillator”)

gives users the option to include RTC functionality to

their applications. This is accomplished with an

inexpensive watch crystal to provide an accurate time

base and several lines of application code to calculate

the time. When operating in Sleep mode and using a

battery or supercapacitor as a power source, it can

completely eliminate the need for a separate RTC

device and battery backup.

The application code routine, RTCisr, shown in

Example 13-1, demonstrates a simple method to

increment a counter at one-second intervals using an

Interrupt Service Routine. Incrementing the TMR1

the routine, which increments the seconds counter by

one. Additional counters for minutes and hours are

incremented as the previous counter overflow.

Since the register pair is 16 bits wide, counting up to

overflow the register directly from a 32.768 kHz clock

would take 2 seconds. To force the overflow at the

required one-second intervals, it is necessary to

preload it. The simplest method is to set the MSb of

TMR1H with a BSF instruction. Note that the TMR1L

introduce cumulative errors over many cycles.

For this method to be accurate, Timer1 must operate in

Asynchronous mode and the Timer1 overflow interrupt

must be enabled (PIE1<0> = 1), as shown in the

routine, RTCinit. The Timer1 oscillator must also be

enabled and running at all times.

VDD

OSC1

VSS

OSC2

RC0

RC1

RC2

Note: Not drawn to scale.

Note: The Special Event Triggers from the

CCP2 module will not set the TMR1IF

interrupt flag bit (PIR1<0>).

PIC18F2221/2321/4221/4321 FAMILY

EXAMPLE 13-1: IMPLEMENTING A REAL-TIME CLOCK USING A TIMER1 INTERRUPT SERVICE

TABLE 13-2: REGISTERS ASSOCIATED WITH TIMER1 AS A TIMER/COUNTER

RTCinit

MOVLW 80h ; Preload TMR1 register pair

MOVWF TMR1H ; for 1 second overflow

CLRF TMR1L

MOVLW b'00001111' ; Configure for external clock,

MOVWF T1CON ; Asynchronous operation, external oscillator

CLRF secs ; Initialize timekeeping registers

CLRF mins ;

MOVLW .12

MOVWF hours

BSF PIE1, TMR1IE ; Enable Timer1 interrupt

RETURN

RTCisr

BSF TMR1H, 7 ; Preload for 1 sec overflow

BCF PIR1, TMR1IF ; Clear interrupt flag

INCF secs, F ; Increment seconds

MOVLW .59 ; 60 seconds elapsed?

CPFSGT secs

RETURN ; No, done

CLRF secs ; Clear seconds

INCF mins, F ; Increment minutes

MOVLW .59 ; 60 minutes elapsed?

CPFSGT mins

RETURN ; No, done

CLRF mins ; clear minutes

INCF hours, F ; Increment hours

MOVLW .23 ; 24 hours elapsed?

CPFSGT hours

RETURN ; No, done

CLRF hours ; Reset hours

RETURN ; Done

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

TMR1L Timer1 Register Low Byte 56

TMR1H Timer1 Register High Byte 56

T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 56

Legend: Shaded cells are not used by the Timer1 module.

Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

14.0 TIMER2 MODULE

The Timer2 timer module incorporates the following

features:

• 8-bit timer and period registers (TMR2 and PR2,

respectively)

• Readable and writable (both registers)

• Software programmable prescaler (1:1, 1:4 and

1:16)

• Software programmable postscaler (1:1 through

1:16)

• Interrupt on TMR2 to PR2 match

• Optional use as the shift clock for the MSSP

module

The module is controlled through the T2CON register

(Register 14-1), which enables or disables the timer

and configures the prescaler and postscaler. Timer2

can be shut off by clearing control bit, TMR2ON

(T2CON<2>), to minimize power consumption.

A simplified block diagram of the module is shown in

Figure 14-1.

14.1 Timer2 Operation

In normal operation, TMR2 is incremented from 00h on

each clock (FOSC/4). A 4-bit counter/prescaler on the

clock input gives direct input, divide-by-4 and divide-by-

16 prescale options. These are selected by the prescaler

control bits, T2CKPS<1:0> (T2CON<1:0>). The value of

TMR2 is compared to that of the Period register, PR2, on

each clock cycle. When the two values match, the com-

parator generates a match signal as the timer output.

This signal also resets the value of TMR2 to 00h on the

next cycle and drives the output counter/postscaler (see

Section 14.2 “Timer2 Interrupt”).

The TMR2 and PR2 registers are both directly readable

and writable. The TMR2 register is cleared on any

device Reset, while the PR2 register initializes at FFh.

Both the prescaler and postscaler counters are cleared

on the following events:

• a write to the TMR2 register

• a write to the T2CON register

• any device Reset (Power-on Reset, MCLR Reset,

Watchdog Timer Reset or Brown-out Reset)

TMR2 is not cleared when T2CON is written.

U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

— T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0

bit 7 bit 0

bit 7 Unimplemented: Read as ‘0’

bit 6-3 T2OUTPS<3:0>: Timer2 Output Postscale Select bits

0000 = 1:1 Postscale

0001 = 1:2 Postscale

•

1111 = 1:16 Postscale

bit 2 TMR2ON: Timer2 On bit

1 = Timer2 is on

0 = Timer2 is off

bit 1-0 T2CKPS<1:0>: Timer2 Clock Prescale Select bits

00 = Prescaler is 1

01 = Prescaler is 4

1x = Prescaler is 16

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

14.2 Timer2 Interrupt

Timer2 can also generate an optional device interrupt.

The Timer2 output signal (TMR2 to PR2 match)

provides the input for the 4-bit output counter/post-

scaler. This counter generates the TMR2 match inter-

rupt flag which is latched in TMR2IF (PIR1<1>). The

interrupt is enabled by setting the TMR2 Match Inter-

rupt Enable bit, TMR2IE (PIE1<1>).

A range of 16 postscale options (from 1:1 through 1:16

inclusive) can be selected with the postscaler control

bits, T2OUTPS<3:0> (T2CON<6:3>).

14.3 Timer2 Output

The unscaled output of TMR2 is available primarily to

the CCP modules, where it is used as a time base for

operations in PWM mode.

Timer2 can be optionally used as the shift clock source

for the MSSP module operating in SPI mode.

Additional information is provided in Section 18.0

“Master Synchronous Serial Port (MSSP) Module”.

FIGURE 14-1: TIMER2 BLOCK DIAGRAM

TABLE 14-1: REGISTERS ASSOCIATED WITH TIMER2 AS A TIMER/COUNTER

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

TMR2 Timer2 Register 56

T2CON — T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 56

PR2 Timer2 Period Register 56

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Timer2 module.

Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.

Comparator

TMR2 Output

TMR2

Postscaler

Prescaler PR2

FOSC/4

1:1 to 1:16

1:1, 1:4, 1:16

T2OUTPS<3:0>

T2CKPS<1:0>

Set TMR2IF

Internal Data Bus

Reset

TMR2/PR2

(to PWM or MSSP)

Match

PIC18F2221/2321/4221/4321 FAMILY

15.0 TIMER3 MODULE

The Timer3 timer/counter module incorporates these

features:

• Software selectable operation as a 16-bit timer or

counter

• Readable and writable 8-bit registers (TMR3H

and TMR3L)

• Selectable clock source (internal or external) with

device clock or Timer1 oscillator internal options

• Interrupt-on-overflow

• Module Reset on CCP Special Event Trigger

A simplified block diagram of the Timer3 module is

shown in Figure 15-1. A block diagram of the module’s

operation in Read/Write mode is shown in Figure 15-2.

The Timer3 module is controlled through the T3CON

options for the CCP modules (see Section 16.1.1

“CCP Modules and Timer Resources” for more

information).

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON

bit 7 bit 0

bit 7 RD16: 16-Bit Read/Write Mode Enable bit

1 = Enables register read/write of Timer3 in one 16-bit operation

0 = Enables register read/write of Timer3 in two 8-bit operations

bit 6,3 T3CCP<2:1>: Timer3 and Timer1 to CCPx Enable bits

1x = Timer3 is the capture/compare clock source for the CCP modules

01 = Timer3 is the capture/compare clock source for CCP2; Timer1 is the capture/compare

clock source for CCP1

00 = Timer1 is the capture/compare clock source for the CCP modules

bit 5-4 T3CKPS<1:0>: Timer3 Input Clock Prescale Select bits

11 = 1:8 Prescale value

10 = 1:4 Prescale value

01 = 1:2 Prescale value

00 = 1:1 Prescale value

bit 2 T3SYNC: Timer3 External Clock Input Synchronization Control bit

(Not usable if the device clock comes from Timer1/Timer3.)

When TMR3CS = 1:

1 = Do not synchronize external clock input

0 = Synchronize external clock input

When TMR3CS = 0:

This bit is ignored. Timer3 uses the internal clock when TMR3CS = 0.

bit 1 TMR3CS: Timer3 Clock Source Select bit

1 = External clock input from Timer1 oscillator or T13CKI (on the rising edge after the first

falling edge)

0 = Internal clock (FOSC/4)

bit 0 TMR3ON: Timer3 On bit

1 = Enables Timer3

0 = Stops Timer3

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

15.1 Timer3 Operation

Timer3 can operate in one of three modes:

•Timer

• Synchronous Counter

• Asynchronous Counter

The operating mode is determined by the clock select

bit, TMR3CS (T3CON<1>). When TMR3CS is cleared

(= 0), Timer3 increments on every internal instruction

cycle (FOSC/4). When the bit is set, Timer3 increments

on every rising edge of the Timer1 external clock input

or the Timer1 oscillator, if enabled.

As with Timer1, the RC1/T1OSI and RC0/T1OSO/

T13CKI pins become inputs when the Timer1 oscillator

is enabled. This means the values of TRISC<1:0> are

ignored and the pins are read as ‘0’.

FIGURE 15-1: TIMER3 BLOCK DIAGRAM (8-BIT READ/WRITE MODE)

FIGURE 15-2: TIMER3 BLOCK DIAGRAM (16-BIT READ/WRITE MODE)

T3SYNC

TMR3CS

T3CKPS<1:0>

Sleep Input

T1OSCEN(1)

FOSC/4

Internal

Clock

Prescaler

1, 2, 4, 8

Synchronize

Detect

T1OSO/T13CKI

T1OSI

TMR3ON

TMR3L Set

TMR3IF

on Overflow

TMR3

High Byte

Timer1 Oscillator

Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.

On/Off

Timer3

CCP1/CCP2 Special Event Trigger

CCP1/CCP2 Select from T3CON<6,3>

Clear TMR3

Timer1 Clock Input

T3SYNC

TMR3CS

T3CKPS<1:0>

Sleep Input

T1OSCEN(1)

FOSC/4

Internal

Clock

Prescaler

1, 2, 4, 8

Synchronize

Detect

T13CKI/T1OSO

T1OSI

Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.

TMR3L

Internal Data Bus

Set

TMR3IF

on Overflow

TMR3

TMR3H

High Byte

Read TMR1L

Write TMR1L

TMR3ON

CCP1/CCP2 Special Event Trigger

Timer1 Oscillator

On/Off

Timer3

Timer1 Clock Input

CCP1/CCP2 Select from T3CON<6,3>

Clear TMR3

PIC18F2221/2321/4221/4321 FAMILY

15.2 Timer3 16-Bit Read/Write Mode

Timer3 can be configured for 16-bit reads and writes

(see Figure 15-2). When the RD16 control bit

(T3CON<7>) is set, the address for TMR3H is mapped

to a buffer register for the high byte of Timer3. A read

from TMR3L will load the contents of the high byte of

Timer3 into the Timer3 High Byte Buffer register. This

provides the user with the ability to accurately read all

16 bits of Timer1 without having to determine whether

a read of the high byte, followed by a read of the low

byte, has become invalid due to a rollover between

reads.

A write to the high byte of Timer3 must also take place

through the TMR3H Buffer register. The Timer3 high

byte is updated with the contents of TMR3H when a

write occurs to TMR3L. This allows a user to write all

16 bits to both the high and low bytes of Timer3 at once.

The high byte of Timer3 is not directly readable or

writable in this mode. All reads and writes must take

place through the Timer3 High Byte Buffer register.

Writes to TMR3H do not clear the Timer3 prescaler.

The prescaler is only cleared on writes to TMR3L.

15.3 Using the Timer1 Oscillator as the

Timer3 Clock Source

The Timer1 internal oscillator may be used as the clock

source for Timer3. The Timer1 oscillator is enabled by

setting the T1OSCEN (T1CON<3>) bit. To use it as the

Timer3 clock source, the TMR3CS bit must also be set.

As previously noted, this also configures Timer3 to

increment on every rising edge of the oscillator source.

The Timer1 oscillator is described in Section 13.0

“Timer1 Module”.

15.4 Timer3 Interrupt

The TMR3 register pair (TMR3H:TMR3L) increments

from 0000h to FFFFh and overflows to 0000h. The

Timer3 interrupt, if enabled, is generated on overflow

and is latched in interrupt flag bit, TMR3IF (PIR2<1>).

This interrupt can be enabled or disabled by setting or

clearing the Timer3 Interrupt Enable bit, TMR3IE

(PIE2<1>).

15.5 Resetting Timer3 Using the CCP

Special Event Trigger

If either of the CCP modules is configured to use Timer3

and to generate a Special Event Trigger in Compare

mode (CCP1M<3:0> or CCP2M<3:0> = 1011), this

signal will reset Timer3. It will also start an A/D conver-

sion if the A/D module is enabled (see Section 16.3.4

“Special Event Trigger” for more information).

The module must be configured as either a timer or

synchronous counter to take advantage of this feature.

When used this way, the CCPR2H:CCPR2L register

pair effectively becomes a period register for Timer3.

If Timer3 is running in Asynchronous Counter mode,

the Reset operation may not work.

In the event that a write to Timer3 coincides with a

Special Event Trigger from a CCP module, the write will

take precedence.

TABLE 15-1: REGISTERS ASSOCIATED WITH TIMER3 AS A TIMER/COUNTER

Note: The Special Event Triggers from the

CCP2 module will not set the TMR3IF

interrupt flag bit (PIR2<1>).

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR2 OSCFIF CMIF —EEIF BCLIF HLVDIF TMR3IF CCP2IF 58

PIE2 OSCFIE CMIE —EEIE BCLIE HLVDIE TMR3IE CCP2IE 58

IPR2 OSCFIP CMIP —EEIP BCLIP HLVDIP TMR3IP CCP2IP 58

TMR3L Timer3 Register Low Byte 57

TMR3H Timer3 Register High Byte 57

T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 56

T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Timer3 module.

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

16.0 CAPTURE/COMPARE/PWM

(CCP) MODULES

PIC18F2221/2321/4221/4321 family devices all have

two CCP (Capture/Compare/PWM) modules. Each

module contains a 16-bit register which can operate as

a 16-bit Capture register, a 16-bit Compare register or

a PWM Master/Slave Duty Cycle register.

In 28-pin devices, the two standard CCP modules

(CCP1 and CCP2) operate as described in this

chapter. In 40/44-pin devices, CCP1 is implemented

as an Enhanced CCP module with standard Capture

and Compare modes and Enhanced PWM modes.

The ECCP implementation is discussed in

Section 17.0 “Enhanced Capture/Compare/PWM

(ECCP) Module”.

The Capture and Compare operations described in this

chapter apply to all standard and Enhanced CCP

modules.

Note: Throughout this section and Section 17.0

“Enhanced Capture/Compare/PWM (ECCP)

Module”, references to the register and bit

names for CCP modules are referred to

generically by the use of ‘x’ or ‘y’ in place

of the specific module number. Thus,

“CCPxCON” might refer to the control regis-

ter for CCP1, CCP2 or ECCP1. “CCPxCON”

is used throughout these sections to refer to

the module control register, regardless of

whether the CCP module is a standard or

Enhanced implementation.

U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

—— DCxB1 DCxB0 CCPxM3 CCPxM2 CCPxM1 CCPxM0

bit 7 bit 0

bit 7-6 Unimplemented: Read as ‘0’

bit 5-4 DCxB<1:0>: PWM Duty Cycle bit 1 and bit 0 for CCP Module x

Capture mode:

Unused.

Compare mode:

Unused.

PWM mode:

These bits are the two LSbs (bit 1 and bit 0) of the 10-bit PWM duty cycle. The eight MSbs

(DCxB<9:2>) of the duty cycle are found in CCPRxL.

bit 3-0 CCPxM<3:0>: CCPx Module Mode Select bits

0000 = Capture/Compare/PWM disabled (resets CCP module)

0001 = Reserved

0010 = Compare mode, toggle output on match (CCPxIF bit is set)

0011 = Reserved

0100 = Capture mode, every falling edge

0101 = Capture mode, every rising edge

0110 = Capture mode, every 4th rising edge

0111 = Capture mode, every 16th rising edge

1000 = Compare mode: initialize CCP pin low; on compare match, force CCP pin high

(CCPxIF bit is set)

1001 = Compare mode: initialize CCP pin high; on compare match, force CCP pin low

(CCPxIF bit is set)

1010 = Compare mode: generate software interrupt on compare match (CCPxIF bit is set,

CCP pin reflects I/O state)

1011 = Compare mode: trigger special event, reset timer, start A/D conversion on

CCPx match (CCPxIF bit is set)

11xx = PWM mode

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

16.1 CCP Module Configuration

Each Capture/Compare/PWM module is associated

with a control register (generically, CCPxCON) and a

data register (CCPRx). The data register, in turn, is

comprised of two 8-bit registers: CCPRxL (low byte)

and CCPRxH (high byte). All registers are both

readable and writable.

16.1.1 CCP MODULES AND TIMER

RESOURCES

The CCP modules utilize Timers 1, 2 or 3, depending

on the mode selected. Timer1 and Timer3 are available

to modules in Capture or Compare modes, while

Timer2 is available for modules in PWM mode.

TABLE 16-1: CCP MODE – TIMER

RESOURCES

The assignment of a particular timer to a module is

determined by the Timer to CCP enable bits in the

T3CON register (Register 15-1). Both modules may be

active at any given time and may share the same timer

resource if they are configured to operate in the same

mode (Capture/Compare or PWM) at the same time. The

interactions between the two modules are summarized in

Figure 16-1 and Figure 16-2. In Timer1 in Asynchronous

Counter mode, the capture operation will not work.

16.1.2 CCP2 PIN ASSIGNMENT

The pin assignment for CCP2 (Capture input, Compare

and PWM output) can change, based on device config-

uration. The CCP2MX Configuration bit determines

which pin CCP2 is multiplexed to. By default, it is

assigned to RC1 (CCP2MX = 1). If the Configuration bit

is cleared, CCP2 is multiplexed with RB3.

Changing the pin assignment of CCP2 does not

automatically change any requirements for configuring

the port pin. Users must always verify that the appropri-

ate TRIS register is configured correctly for CCP2

operation, regardless of where it is located.

TABLE 16-2: INTERACTIONS BETWEEN CCP1 AND CCP2 FOR TIMER RESOURCES

CCP/ECCP Mode Timer Resource

Capture

Compare

PWM

Timer1 or Timer3

Timer2

CCP1 Mode CCP2 Mode Interaction

Capture Capture Each module can use TMR1 or TMR3 as the time base. The time base can be different

for each CCP.

Capture Compare CCP2 can be configured for the Special Event Trigger to reset TMR1 or TMR3

(depending upon which time base is used). Automatic A/D conversions on trigger event

can also be done. Operation of CCP1 could be affected if it is using the same timer as a

time base.

Compare Capture CCP1 can be configured for the Special Event Trigger to reset TMR1 or TMR3

(depending upon which time base is used). Operation of CCP2 could be affected if it is

using the same timer as a time base.

Compare Compare Either module can be configured for the Special Event Trigger to reset the time base.

Automatic A/D conversions on CCP2 trigger event can be done. Conflicts may occur if

both modules are using the same time base.

Capture PWM(1) None

Compare PWM(1) None

PWM(1) Capture None

PWM(1) Compare None

PWM(1) PWM Both PWMs will have the same frequency and update rate (TMR2 interrupt).

Note 1: Includes standard and Enhanced PWM operation.

PIC18F2221/2321/4221/4321 FAMILY

16.2 Capture Mode

In Capture mode, the CCPRxH:CCPRxL register pair

captures the 16-bit value of the TMR1 or TMR3

registers when an event occurs on the corresponding

CCPx pin. An event is defined as one of the following:

• every falling edge

• every rising edge

• every 4th rising edge

• every 16th rising edge

The event is selected by the mode select bits,

CCPxM<3:0> (CCPxCON<3:0>). When a capture is

made, the interrupt request flag bit, CCPxIF, is set; it

must be cleared in software. If another capture occurs

before the value in register CCPRx is read, the old

captured value is overwritten by the new captured value.

16.2.1 CCP PIN CONFIGURATION

In Capture mode, the appropriate CCPx pin should be

configured as an input by setting the corresponding

TRIS direction bit.

16.2.2 TIMER1/TIMER3 MODE SELECTION

The timers that are to be used with the capture feature

(Timer1 and/or Timer3) must be running in Timer mode or

Synchronized Counter mode. In Asynchronous Counter

mode, the capture operation will not work. The timer to be

used with each CCP module is selected in the T3CON

Resources”).

16.2.3 SOFTWARE INTERRUPT

When the Capture mode is changed, a false capture

interrupt may be generated. The user should keep the

CCPxIE interrupt enable bit clear to avoid false

interrupts. The interrupt flag bit, CCPxIF, should also be

cleared following any such change in operating mode.

16.2.4 CCP PRESCALER

There are four prescaler settings in Capture mode.

They are specified as part of the operating mode

selected by the mode select bits (CCPxM<3:0>).

Whenever the CCP module is turned off or Capture

mode is disabled, the prescaler counter is cleared. This

means that any Reset will clear the prescaler counter.

Switching from one capture prescaler to another may

generate an interrupt. Also, the prescaler counter will

not be cleared; therefore, the first capture may be from

a non-zero prescaler. Example 16-1 shows the

recommended method for switching between capture

prescalers. This example also clears the prescaler

counter and will not generate the “false” interrupt.

EXAMPLE 16-1: CHANGING BETWEEN

CAPTURE PRESCALERS

(CCP2 SHOWN)

FIGURE 16-1: CAPTURE MODE OPERATION BLOCK DIAGRAM

Note: If RB3/CCP2 or RC1/CCP2 is configured

as an output, a write to the port can cause

a capture condition.

CLRF CCP2CON ; Turn CCP module off

MOVLW NEW_CAPT_PS ; Load WREG with the

; new prescaler mode

; value and CCP ON

MOVWF CCP2CON ; Load CCP2CON with

; this value

CCPR1H CCPR1L

TMR1H TMR1L

Set CCP1IF

TMR3

Enable

Q1:Q4

CCP1CON<3:0>

CCP1 pin

Prescaler

÷ 1, 4, 16

and

Edge Detect

TMR1

Enable

T3CCP2

CCPR2H CCPR2L

TMR1H TMR1L

Set CCP2IF

TMR3

Enable

CCP2CON<3:0>

CCP2 pin

Prescaler

÷ 1, 4, 16

TMR3H TMR3L

TMR1

Enable

T3CCP2

T3CCP1

T3CCP2

T3CCP1

TMR3H TMR3L

and

Edge Detect

PIC18F2221/2321/4221/4321 FAMILY

16.3 Compare Mode

In Compare mode, the 16-bit CCPRx register value is

constantly compared against either the TMR1 or TMR3

can be:

• driven high

• driven low

• toggled (high-to-low or low-to-high)

• remain unchanged (that is, reflects the state of the

I/O latch)

The action on the pin is based on the value of the mode

select bits (CCPxM<3:0>). At the same time, the

interrupt flag bit, CCPxIF, is set.

16.3.1 CCP PIN CONFIGURATION

The user must configure the CCPx pin as an output by

clearing the appropriate TRIS bit.

16.3.2 TIMER1/TIMER3 MODE SELECTION

Timer1 and/or Timer3 must be running in Timer mode

or Synchronized Counter mode if the CCP module is

using the compare feature. In Asynchronous Counter

mode, the compare operation may not work.

16.3.3 SOFTWARE INTERRUPT MODE

When the Generate Software Interrupt mode is chosen

(CCPxM<3:0> = 1010), the corresponding CCPx pin is

not affected. Only a CCP interrupt is generated, if

enabled and the CCPxIE bit is set.

16.3.4 SPECIAL EVENT TRIGGER

Both CCP modules are equipped with a Special Event

Trigger. This is an internal hardware signal generated

in Compare mode to trigger actions by other modules.

The Special Event Trigger is enabled by selecting

the Compare Special Event Trigger mode

(CCPxM<3:0> = 1011).

For either CCP module, the Special Event Trigger resets

the Timer register pair for whichever timer resource is

currently assigned as the module’s time base. This

allows the CCPRx registers to serve as a programmable

period register for either timer.

The Special Event Trigger for CCP2 can also start an

A/D conversion. In order to do this, the A/D converter

must already be enabled.

FIGURE 16-2: COMPARE MODE OPERATION BLOCK DIAGRAM

Note: Clearing the CCP2CON register will force

the RB3 or RC1 compare output latch

(depending on device configuration) to the

default low level. This is not the PORTB or

PORTC I/O data latch.

CCPR1H CCPR1L

TMR1H TMR1L

Comparator Q

Output

Logic

Special Event Trigger

Set CCP1IF

CCP1 pin

TRIS

CCP1CON<3:0>

Output Enable

TMR3H TMR3L

CCPR2H CCPR2L

Comparator

T3CCP2

T3CCP1

Set CCP2IF

Compare

(Timer1/Timer3 Reset)

Output

Logic

Special Event Trigger

CCP2 pin

TRIS

CCP2CON<3:0>

Output Enable

(Timer1/Timer3 Reset, A/D Trigger)

Match

Compare

Match

PIC18F2221/2321/4221/4321 FAMILY

TABLE 16-3: REGISTERS ASSOCIATED WITH CAPTURE, COMPARE, TIMER1 AND TIMER3

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

RCON IPEN

SBOREN

(1)

—RI TO PD POR BOR 54

PIR1 PSPIF(2) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(2) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(2) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

PIR2 OSCFIF CMIF —EEIF BCLIF HLVDIF TMR3IF CCP2IF 58

PIE2 OSCFIE CMIE —EEIE BCLIE HLVDIE TMR3IE CCP2IE 58

IPR2 OSCFIP CMIP —EEIP BCLIP HLVDIP TMR3IP CCP2IP 58

TRISB PORTB Data Direction Register 58

TRISC PORTC Data Direction Register 58

TMR1L Timer1 Register Low Byte 56

TMR1H Timer1 Register High Byte 56

T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 56

TMR3H Timer3 Register High Byte 57

TMR3L Timer3 Register Low Byte 57

T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 57

CCPR1L Capture/Compare/PWM Register 1 Low Byte 57

CCPR1H Capture/Compare/PWM Register 1 High Byte 57

CCP1CON P1M1(2) P1M0(2) DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 57

CCPR2L Capture/Compare/PWM Register 2 Low Byte 57

CCPR2H Capture/Compare/PWM Register 2 High Byte 57

CCP2CON — — DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by Capture/Compare, Timer1 or Timer3.

Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled

and reads as ‘0’. See Section 5.4 “Brown-out Reset (BOR)”.

2: These bits are unimplemented on 28-pin devices and read as ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

16.4 PWM Mode

In Pulse-Width Modulation (PWM) mode, the CCPx pin

produces up to a 10-bit resolution PWM output. Since

the CCP2 pin is multiplexed with a PORTB or PORTC

data latch, the appropriate TRIS bit must be cleared to

make the CCP2 pin an output.

Figure 16-3 shows a simplified block diagram of the

CCP module in PWM mode.

For a step-by-step procedure on how to set up the CCP

module for PWM operation, see Section 16.4.4

“Setup for PWM Operation”.

FIGURE 16-3: SIMPLIFIED PWM BLOCK

DIAGRAM

A PWM output (Figure 16-4) has a time base (period)

and a time that the output stays high (duty cycle).

The frequency of the PWM is the inverse of the

period (1/period).

FIGURE 16-4: PWM OUTPUT

16.4.1 PWM PERIOD

The PWM period is specified by writing to the PR2

following formula:

EQUATION 16-1:

PWM frequency is defined as 1/[PWM period].

When TMR2 is equal to PR2, the following three events

occur on the next increment cycle:

•TMR2 is cleared

• The CCPx pin is set (exception: if PWM duty

cycle = 0%, the CCPx pin will not be set)

• The PWM duty cycle is latched from CCPRxL into

CCPRxH

16.4.2 PWM DUTY CYCLE

The PWM duty cycle is specified by writing to the

CCPRxL register and to the CCPxCON<5:4> bits. Up

to 10-bit resolution is available. The CCPRxL contains

the eight MSbs and the CCPxCON<5:4> contains the

two LSbs. This 10-bit value is represented by

CCPRxL:CCPxCON<5:4>. The following equation is

used to calculate the PWM duty cycle in time:

EQUATION 16-2:

CCPRxL and CCPxCON<5:4> can be written to at any

time, but the duty cycle value is not latched into

CCPRxH until after a match between PR2 and TMR2

occurs (i.e., the period is complete). In PWM mode,

CCPRxH is a read-only register.

Note: Clearing the CCP2CON register will force

the RB3 or RC1 output latch (depending on

device configuration) to the default low

level. This is not the PORTB or PORTC I/O

data latch.

CCPRxL

CCPRxH (Slave)

Comparator

TMR2

Comparator

PR2

(Note 1)

Duty Cycle Registers CCPxCON<5:4>

Clear Timer,

CCPx pin and

latch D.C.

Note 1: The 8-bit TMR2 value is concatenated with the 2-bit

internal Q clock, or 2 bits of the prescaler, to create the

10-bit time base.

CCPx Output

Corresponding

TRIS bit

Period

Duty Cycle

TMR2 = PR2

TMR2 = Duty Cycle

TMR2 = PR2

Note: The Timer2 postscalers (see Section 14.0

“Timer2 Module”) are not used in the

determination of the PWM frequency. The

postscaler could be used to have a servo

update rate at a different frequency than

the PWM output.

PWM Period = [(PR2) + 1] • 4 • TOSC •

(TMR2 Prescale Value)

PWM Duty Cycle = (CCPRXL:CCPXCON<5:4>) •

TOSC • (TMR2 Prescale Value)

PIC18F2221/2321/4221/4321 FAMILY

The CCPRxH register and a 2-bit internal latch are

used to double-buffer the PWM duty cycle. This

double-buffering is essential for glitchless PWM

operation.

When the CCPRxH and 2-bit latch match TMR2,

concatenated with an internal 2-bit Q clock or 2 bits of

the TMR2 prescaler, the CCPx pin is cleared.

The maximum PWM resolution (bits) for a given PWM

frequency is given by the equation:

EQUATION 16-3:

TABLE 16-4: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz

16.4.3 PWM AUTO-SHUTDOWN

(CCP1 ONLY)

The PWM auto-shutdown features of the Enhanced CCP

module are also available to CCP1 in 28-pin devices. The

operation of this feature is discussed in detail in

Section 17.4.7 “Enhanced PWM Auto-Shutdown”.

Auto-shutdown features are not available for CCP2.

16.4.4 SETUP FOR PWM OPERATION

The following steps should be taken when configuring

the CCP module for PWM operation:

1. Set the PWM period by writing to the PR2

2. Set the PWM duty cycle by writing to the

CCPRxL register and CCPxCON<5:4> bits.

3. Make the CCPx pin an output by clearing the

appropriate TRIS bit.

4. Set the TMR2 prescale value, then enable

Timer2 by writing to T2CON.

5. Configure the CCPx module for PWM operation.

Note: If the PWM duty cycle value is longer than

the PWM period, the CCPx pin will not be

cleared.

FOSC

FPWM

---------------

⎝⎠

⎛⎞

log

2()log

----------------------------- b i t s=

PWM Resolution (max)

PWM Frequency 2.44 kHz 9.77 kHz 39.06 kHz 156.25 kHz 312.50 kHz 416.67 kHz

Timer Prescaler (1, 4, 16)1641111

PR2 Value FFh FFh FFh 3Fh 1Fh 17h

Maximum Resolution (bits) 10 10 10 8 7 6.58

PIC18F2221/2321/4221/4321 FAMILY

TABLE 16-5: REGISTERS ASSOCIATED WITH PWM AND TIMER2

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

RCON IPEN SBOREN(1) —RI TO PD POR BOR 54

PIR1 PSPIF(2) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(2) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(2) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

TRISB PORTB Data Direction Register 58

TRISC PORTC Data Direction Register 58

TMR2 Timer2 Register 56

PR2 Timer2 Period Register 56

T2CON — T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 56

CCPR1L Capture/Compare/PWM Register 1 Low Byte 57

CCPR1H Capture/Compare/PWM Register 1 High Byte 57

CCP1CON P1M1(2) P1M0(2) DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 57

CCPR2L Capture/Compare/PWM Register 2 Low Byte 57

CCPR2H Capture/Compare/PWM Register 2 High Byte 57

CCP2CON —— DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 57

ECCP1AS ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1(2) PSSBD0(2) 57

ECCP1DEL PRSEN PDC6(2) PDC5(2) PDC4(2) PDC3(2) PDC2(2) PDC1(2) PDC0(2) 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PWM or Timer2.

Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled

and reads as ‘0’. See Section 5.4 “Brown-out Reset (BOR)”.

2: These bits are unimplemented on 28-pin devices and read as ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

17.0 ENHANCED CAPTURE/

COMPARE/PWM (ECCP)

MODULE

In PIC18F4221/4321 devices, CCP1 is implemented

as a standard CCP module with Enhanced PWM

capabilities. These include the provision for 2 or

4 output channels, user-selectable polarity, dead-band

control and automatic shutdown and restart. The

Enhanced features are discussed in detail in

Section 17.4 “Enhanced PWM Mode”. Capture,

Compare and single-output PWM functions of the

ECCP module are the same as described for the

standard CCP module.

The control register for the Enhanced CCP module is

shown in Register 17-1. It differs from the CCPxCON

registers in PIC18F2221/2321 devices in that the two

Most Significant bits are implemented to control PWM

functionality.

Note: The ECCP module is implemented only in

40/44-pin devices.

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

P1M1 P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0

bit 7 bit 0

bit 7-6 P1M<1:0>: Enhanced PWM Output Configuration bits

If CCP1M<3:2> = 00, 01, 10:

xx = P1A assigned as Capture/Compare input/output; P1B, P1C, P1D assigned as port pins

If CCP1M<3:2> = 11:

00 = Single output: P1A modulated; P1B, P1C, P1D assigned as port pins

01 = Full-bridge output forward: P1D modulated; P1A active; P1B, P1C inactive

10 = Half-bridge output: P1A, P1B modulated with dead-band control; P1C, P1D assigned

as port pins

11 = Full-bridge output reverse: P1B modulated; P1C active; P1A, P1D inactive

bit 5-4 DC1B<1:0>: PWM Duty Cycle bit 1 and bit 0

Capture mode:

Unused.

Compare mode:

Unused.

PWM mode:

These bits are the two LSbs of the 10-bit PWM duty cycle. The eight MSbs of the duty cycle are

found in CCPR1L.

bit 3-0 CCP1M<3:0>: Enhanced CCP Mode Select bits

0000 = Capture/Compare/PWM off (resets ECCP module)

0001 = Reserved

0010 = Compare mode, toggle output on match

0011 = Capture mode

0100 = Capture mode, every falling edge

0101 = Capture mode, every rising edge

0110 = Capture mode, every 4th rising edge

0111 = Capture mode, every 16th rising edge

1000 = Compare mode, initialize CCP1 pin low, set output on compare match (set CCP1IF)

1001 = Compare mode, initialize CCP1 pin high, clear output on compare match (set CCP1IF)

1010 = Compare mode, generate software interrupt only, CCP1 pin reverts to I/O state

1011 = Compare mode, trigger special event (ECCP resets TMR1 or TMR3, sets CC1IF bit)

1100 = PWM mode; P1A, P1C active-high; P1B, P1D active-high

1101 = PWM mode; P1A, P1C active-high; P1B, P1D active-low

1110 = PWM mode; P1A, P1C active-low; P1B, P1D active-high

1111 = PWM mode; P1A, P1C active-low; P1B, P1D active-low

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

In addition to the expanded range of modes available

through the CCP1CON and ECCP1AS registers, the

ECCP module has an additional register associated

with Enhanced PWM operation and auto-shutdown

features; it is:

• ECCP1DEL (PWM Dead-Band Delay)

17.1 ECCP Outputs and Configuration

The Enhanced CCP module may have up to four PWM

outputs, depending on the selected operating mode.

These outputs, designated P1A through P1D, are

multiplexed with I/O pins on PORTC and PORTD. The

outputs that are active depend on the CCP operating

mode selected. The pin assignments are summarized

in Table 17-1.

To configure the I/O pins as PWM outputs, the proper

PWM mode must be selected by setting the P1M<1:0>

and CCP1M<3:0> bits. The appropriate TRISC and

TRISD direction bits for the port pins must also be set

as outputs.

17.1.1 ECCP MODULES AND TIMER

RESOURCES

Like the standard CCP modules, the ECCP module can

utilize Timers 1, 2 or 3, depending on the mode

selected. Timer1 and Timer3 are available for modules

in Capture or Compare modes, while Timer2 is avail-

able for modules in PWM mode. Interactions between

the standard and Enhanced CCP modules are identical

to those described for standard CCP modules.

Additional details on timer resources are provided in

Section 16.1.1 “CCP Modules and Timer

Resources”.

17.2 Capture and Compare Modes

Except for the operation of the Special Event Trigger

discussed below, the Capture and Compare modes of

the ECCP module are identical in operation to that of

CCP2. These are discussed in detail in Section 16.2

“Capture Mode” and Section 16.3 “Compare

Mode”. No changes are required when moving

between 28-pin and 40/44-pin devices.

17.2.1 SPECIAL EVENT TRIGGER

The Special Event Trigger output of ECCP1 resets the

TMR1 or TMR3 register pair, depending on which timer

resource is currently selected. This allows the CCPR1

17.3 Standard PWM Mode

When configured in Single Output mode, the ECCP

module functions identically to the standard CCP

module in PWM mode, as described in Section 16.4

“PWM Mode”. This is also sometimes referred to as

“Compatible CCP” mode, as in Table 17-1.

TABLE 17-1: PIN ASSIGNMENTS FOR VARIOUS ECCP1 MODES

Note: When setting up single output PWM

operations, users are free to use either

of the processes described in

Section 16.4.4 “Setup for PWM

Operation” or Section 17.4.9 “Setup

for PWM Operation”. The latter is more

generic and will work for either single or

multi-output PWM.

ECCP Mode CCP1CON

Configuration RC2 RD5 RD6 RD7

All 40/44-pin devices:

Compatible CCP 00xx 11xx CCP1 RD5/PSP5 RD6/PSP6 RD7/PSP7

Dual PWM 10xx 11xx P1A P1B RD6/PSP6 RD7/PSP7

Quad PWM x1xx 11xx P1A P1B P1C P1D

Legend: x = Don’t care. Shaded cells indicate pin assignments not used by ECCP1 in a given mode.

PIC18F2221/2321/4221/4321 FAMILY

17.4 Enhanced PWM Mode

The Enhanced PWM mode provides additional PWM

output options for a broader range of control applica-

tions. The module is a backward compatible version of

the standard CCP module and offers up to four outputs,

designated P1A through P1D. Users are also able to

select the polarity of the signal (either active-high or

active-low). The module’s output mode and polarity are

configured by setting the P1M<1:0> and CCP1M<3:0>

bits of the CCP1CON register.

Figure 17-1 shows a simplified block diagram of PWM

operation. All control registers are double-buffered and

are loaded at the beginning of a new PWM cycle (the

period boundary when Timer2 resets) in order to

prevent glitches on any of the outputs. The exception is

the PWM Dead-Band Delay register, ECCP1DEL,

which is loaded at either the duty cycle boundary or the

period boundary (whichever comes first). Because of

the buffering, the module waits until the assigned timer

resets, instead of starting immediately. This means that

Enhanced PWM waveforms do not exactly match the

standard PWM waveforms, but are instead offset by

one full instruction cycle (4 TOSC).

As before, the user must manually configure the

appropriate TRIS bits for output.

17.4.1 PWM PERIOD

The PWM period is specified by writing to the PR2

following equation.

EQUATION 17-1:

PWM frequency is defined as 1/[PWM period]. When

TMR2 is equal to PR2, the following three events occur

on the next increment cycle:

•TMR2 is cleared

• The CCP1 pin is set (if PWM duty cycle = 0%, the

CCP1 pin will not be set)

• The PWM duty cycle is copied from CCPR1L into

CCPR1H

FIGURE 17-1: SIMPLIFIED BLOCK DIAGRAM OF THE ENHANCED PWM MODULE

Note: The Timer2 postscaler (see Section 14.0

“Timer2 Module”) is not used in the

determination of the PWM frequency. The

postscaler could be used to have a servo

update rate at a different frequency than

the PWM output.

PWM Period = [(PR2) + 1] • 4 • TOSC •

(TMR2 Prescale Value)

CCPR1L

CCPR1H (Slave)

Comparator

TMR2

Comparator

PR2

(Note 1)

Duty Cycle Registers

CCP1CON<5:4>

Clear Timer,

set CCP1 pin and

latch D.C.

Note: The 8-bit TMR2 register is concatenated with the 2-bit internal Q clock, or 2 bits of the prescaler, to create the 10-bit

time base.

TRISx<x>

CCP1/P1A

TRISx<x>

P1B

TRISx<x>

P1D

Output

Controller

P1M1<1:0>

CCP1M<3:0>

ECCP1DEL

CCP1/P1A

P1B

P1C

P1D

P1C

PIC18F2221/2321/4221/4321 FAMILY

17.4.2 PWM DUTY CYCLE

The PWM duty cycle is specified by writing to the

CCPR1L register and to the CCP1CON<5:4> bits. Up

to 10-bit resolution is available. The CCPR1L contains

the eight MSbs and the CCP1CON<5:4> contains the

two LSbs. This 10-bit value is represented by

CCPR1L:CCP1CON<5:4>. The PWM duty cycle is

calculated by the following equation.

EQUATION 17-2:

CCPR1L and CCP1CON<5:4> can be written to at any

time, but the duty cycle value is not copied into

CCPR1H until a match between PR2 and TMR2 occurs

(i.e., the period is complete). In PWM mode, CCPR1H

is a read-only register.

The CCPR1H register and a 2-bit internal latch are

used to double-buffer the PWM duty cycle. This

double-buffering is essential for glitchless PWM

operation. When the CCPR1H and 2-bit latch match

TMR2, concatenated with an internal 2-bit Q clock or

two bits of the TMR2 prescaler, the CCP1 pin is

cleared. The maximum PWM resolution (bits) for a

given PWM frequency is given by the following

equation.

EQUATION 17-3:

17.4.3 PWM OUTPUT CONFIGURATIONS

The P1M<1:0> bits in the CCP1CON register allow one

of four configurations:

• Single Output

• Half-Bridge Output

• Full-Bridge Output, Forward mode

• Full-Bridge Output, Reverse mode

The Single Output mode is the standard PWM mode

discussed in Section 17.4 “Enhanced PWM Mode”.

The Half-Bridge and Full-Bridge Output modes are

covered in detail in the sections that follow.

The general relationship of the outputs in all

configurations is summarized in Figure 17-2.

TABLE 17-2: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz

PWM Duty Cycle = (CCPR1L:CCP1CON<5:4>) •

TOSC • (TMR2 Prescale Value)

Note: If the PWM duty cycle value is longer than

the PWM period, the CCP1 pin will not be

cleared.

()

PWM Resolution (max) =

FOSC

FPWM

log

log(2) bits

PWM Frequency 2.44 kHz 9.77 kHz 39.06 kHz 156.25 kHz 312.50 kHz 416.67 kHz

Timer Prescaler (1, 4, 16)1641111

PR2 Value FFh FFh FFh 3Fh 1Fh 17h

Maximum Resolution (bits) 10 10 10 8 7 6.58

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 17-2: PWM OUTPUT RELATIONSHIPS (ACTIVE-HIGH STATE)

FIGURE 17-3: PWM OUTPUT RELATIONSHIPS (ACTIVE-LOW STATE)

Period

SIGNAL PR2 + 1

CCP1CON

<7:6>

P1A Modulated

P1B Modulated

P1A Active

P1B Inactive

P1C Inactive

P1D Modulated

P1A Inactive

P1B Modulated

P1C Active

P1D Inactive

Duty

Cycle

(Single Output)

(Half-Bridge)

(Full-Bridge,

Forward)

(Full-Bridge,

Reverse)

Delay(1) Delay(1)

Period

SIGNAL PR2 + 1

CCP1CON

<7:6>

P1A Modulated

P1B Modulated

P1A Active

P1B Inactive

P1C Inactive

P1D Modulated

P1A Inactive

P1B Modulated

P1C Active

P1D Inactive

Duty

Cycle

(Single Output)

(Half-Bridge)

(Full-Bridge,

Forward)

(Full-Bridge,

Reverse)

Delay(1) Delay(1)

Relationships:

• Period = 4 * T

OSC * (PR2 + 1) * (TMR2 Prescale Value)

• Duty Cycle = TOSC * (CCPR1L<7:0>:CCP1CON<5:4>) * (TMR2 Prescale Value)

• Delay = 4 * TOSC * (ECCP1DEL<6:0>)

Note 1: Dead-band delay is programmed using the ECCP1DEL register (see Section 17.4.6 “Programmable

Dead-Band Delay”).

PIC18F2221/2321/4221/4321 FAMILY

17.4.4 HALF-BRIDGE MODE

In the Half-Bridge Output mode, two pins are used as

outputs to drive push-pull loads. The PWM output signal

is output on the P1A pin, while the complementary PWM

output signal is output on the P1B pin (Figure 17-4). This

mode can be used for half-bridge applications, as shown

in Figure 17-5, or for full-bridge applications where four

power switches are being modulated with two PWM

signals.

In Half-Bridge Output mode, the programmable dead-

band delay can be used to prevent shoot-through

current in half-bridge power devices. The value of bits,

PDC<6:0>, sets the number of instruction cycles before

the output is driven active. If the value is greater than

the duty cycle, the corresponding output remains

inactive during the entire cycle. See Section 17.4.6

“Programmable Dead-Band Delay” for more details

of the dead-band delay operations.

Since the P1A and P1B outputs are multiplexed with

the PORTC<2> and PORTD<5> data latches, the

TRISC<2> and TRISD<5> bits must be cleared to

configure P1A and P1B as outputs.

FIGURE 17-4: HALF-BRIDGE PWM

OUTPUT

FIGURE 17-5: EXAMPLES OF HALF-BRIDGE OUTPUT MODE APPLICATIONS

Period

Duty Cycle

(1)

P1A(2)

P1B(2)

td = Dead-Band Delay

Period

(1) (1)

Note 1: At this time, the TMR2 register is equal to the

PR2 register.

2: Output signals are shown as active-high.

PIC18F4X21

P1A

P1B

FET

Driver

FET

Driver

V+

V-

Load

FET

Driver

FET

Driver

V+

V-

Load

FET

Driver

FET

Driver

PIC18F4X21

P1A

P1B

Standard Half-Bridge Circuit (“Push-Pull”)

Half-Bridge Output Driving a Full-Bridge Circuit

PIC18F2221/2321/4221/4321 FAMILY

17.4.5 FULL-BRIDGE MODE

In Full-Bridge Output mode, four pins are used as

outputs; however, only two outputs are active at a time.

In the Forward mode, pin P1A is continuously active

and pin P1D is modulated. In the Reverse mode, pin

P1C is continuously active and pin P1B is modulated.

These are illustrated in Figure 17-6.

P1A, P1B, P1C and P1D outputs are multiplexed with

the PORTC<2> and PORTD<7:5> data latches. The

TRISC<2> and TRISD<7:5> bits must be cleared to

make the P1A, P1B, P1C and P1D pins outputs.

FIGURE 17-6: FULL-BRIDGE PWM OUTPUT

Period

Duty Cycle

P1A(2)

P1B(2)

P1C(2)

P1D(2)

Forward Mode

(1)

Period

Duty Cycle

P1A(2)

P1C(2)

P1D(2)

P1B(2)

Reverse Mode

(1)

Note 1: At this time, the TMR2 register is equal to the PR2 register.

Note 2: Output signal is shown as active-high.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 17-7: EXAMPLE OF FULL-BRIDGE APPLICATION

17.4.5.1 Direction Change in Full-Bridge Mode

In the Full-Bridge Output mode, the P1M1 bit in the

CCP1CON register allows user to control the forward/

reverse direction. When the application firmware

changes this direction control bit, the module will

assume the new direction on the next PWM cycle.

Just before the end of the current PWM period, the

modulated outputs (P1B and P1D) are placed in their

inactive state, while the unmodulated outputs (P1A and

P1C) are switched to drive in the opposite direction.

This occurs in a time interval of 4 TOSC * (Timer2

Prescale Value) before the next PWM period begins.

The Timer2 prescaler will be either 1, 4 or 16, depend-

ing on the value of the T2CKPS<1:0> bits

(T2CON<1:0>). During the interval from the switch of

the unmodulated outputs to the beginning of the next

period, the modulated outputs (P1B and P1D) remain

inactive. This relationship is shown in Figure 17-8.

Note that in the Full-Bridge Output mode, the ECCP1

module does not provide any dead-band delay. In

general, since only one output is modulated at all times,

dead-band delay is not required. However, there is a

situation where a dead-band delay might be required.

This situation occurs when both of the following

conditions are true:

1. The direction of the PWM output changes when

the duty cycle of the output is at or near 100%.

2. The turn-off time of the power switch, including

the power device and driver circuit, is greater

than the turn-on time.

Figure 17-9 shows an example where the PWM

direction changes from forward to reverse at a near

100% duty cycle. At time t1, the outputs P1A and P1D

become inactive, while output P1C becomes active. In

this example, since the turn-off time of the power

devices is longer than the turn-on time, a shoot-through

current may flow through power devices, QC and QD

(see Figure 17-7), for the duration of ‘t’. The same

phenomenon will occur to power devices, QA and QB,

for PWM direction change from reverse to forward.

If changing PWM direction at high duty cycle is required

for an application, one of the following requirements

must be met:

1. Reduce PWM for a PWM period before

changing directions.

2. Use switch drivers that can drive the switches off

faster than they can drive them on.

Other options to prevent shoot-through current may

exist.

P1A

P1C

FET

Driver

FET

Driver

V+

V-

Load

FET

Driver

FET

Driver

P1B

P1D

QB QD

PIC18F4X21

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 17-8: PWM DIRECTION CHANGE

FIGURE 17-9: PWM DIRECTION CHANGE AT NEAR 100% DUTY CYCLE

Period(1)

SIGNAL

Note 1: The direction bit in the CCP1 Control register (CCP1CON<7>) is written any time during the PWM cycle.

2: When changing directions, the P1A and P1C signals switch before the end of the current PWM cycle at intervals

of 4 TOSC, 16 TOSC or 64 TOSC, depending on the Timer2 prescaler value. The modulated P1B and P1D signals

are inactive at this time.

Period

(Note 2)

P1A (Active-High)

P1B (Active-High)

P1C (Active-High)

P1D (Active-High)

Forward Period Reverse Period

P1A(1)

tON(2)

tOFF(3)

t = tOFF – tON(2,3)

P1B(1)

P1C(1)

P1D(1)

External Switch D(1)

Potential

Shoot-Through

Current(1)

Note 1: All signals are shown as active-high.

2: tON is the turn-on delay of power switch QC and its driver.

3: tOFF is the turn-off delay of power switch QD and its driver.

External Switch C(1)

PIC18F2221/2321/4221/4321 FAMILY

17.4.6 PROGRAMMABLE DEAD-BAND

DELAY

In half-bridge applications, where all power switches

are modulated at the PWM frequency at all times, the

power switches normally require more time to turn off

than to turn on. If both the upper and lower power

switches are switched at the same time (one turned on

and the other turned off), both switches may be on for

a short period of time until one switch completely turns

off. During this brief interval, a very high current (shoot-

through current) may flow through both power

switches, shorting the bridge supply. To avoid this

potentially destructive shoot-through current from

flowing during switching, turning on either of the power

switches is normally delayed to allow the other switch

to completely turn off.

In the Half-Bridge Output mode, a digitally programmable

dead-band delay is available to avoid shoot-through

current from destroying the bridge power switches. The

delay occurs at the signal transition from the nonactive

state to the active state (see Figure 17-4 for illustra-

tion). Bits PDC<6:0> of the ECCP1DEL register

(Register 17-2) set the delay period in terms of micro-

controller instruction cycles (TCY or 4 TOSC). These bits

are not available on 28-pin devices as the standard

CCP module does not support half-bridge operation.

17.4.7 ENHANCED PWM AUTO-SHUTDOWN

When the ECCP1 is programmed for any of the

Enhanced PWM modes, the active output pins may be

configured for auto-shutdown. Auto-shutdown immedi-

ately places the Enhanced PWM output pins into a

defined shutdown state when a shutdown event occurs.

A shutdown event can be caused by either of the

comparator modules, a low level on the Fault input pin

(FLT0) or any combination of these three sources. The

comparators may be used to monitor a voltage input

proportional to a current being monitored in the bridge

circuit. If the voltage exceeds a threshold, the

comparator switches state and triggers a shutdown.

Alternatively, a low digital signal on FLT0 can also trigger

a shutdown. The auto-shutdown feature can be disabled

by not selecting any auto-shutdown sources. The auto-

shutdown sources to be used are selected using the

ECCPAS<2:0> bits (ECCP1AS<6:4>).

When a shutdown occurs, the output pins are asyn-

chronously placed in their shutdown states, specified

by the PSSAC<1:0> and PSSBD<1:0> bits

(ECCP1AS<3:0>). Each pin pair (P1A/P1C and P1B/

P1D) may be set to drive high, drive low or be tri-stated

(not driving). The ECCPASE bit (ECCP1AS<7>) is also

set to hold the Enhanced PWM outputs in their

shutdown states.

The ECCPASE bit is set by hardware when a shutdown

event occurs. If automatic restarts are not enabled, the

ECCPASE bit is cleared by firmware when the cause of

the shutdown clears. If automatic restarts are enabled,

the ECCPASE bit is automatically cleared when the

cause of the auto-shutdown has cleared.

If the ECCPASE bit is set when a PWM period begins,

the PWM outputs remain in their shutdown state for that

entire PWM period. When the ECCPASE bit is cleared,

the PWM outputs will return to normal operation at the

beginning of the next PWM period.

Note: Programmable dead-band delay is not

implemented in 28-pin devices with

standard CCP modules.

Note: Writing to the ECCPASE bit is disabled

while a shutdown condition is active.

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

PRSEN PDC6(1) PDC5(1) PDC4(1) PDC3(1) PDC2(1) PDC1(1) PDC0(1)

bit 7 bit 0

bit 7 PRSEN: PWM Restart Enable bit

1 = Upon auto-shutdown, the ECCPASE bit clears automatically once the shutdown event

goes away; the PWM restarts automatically

0 = Upon auto-shutdown, ECCPASE must be cleared in software to restart the PWM

bit 6-0 PDC<6:0>: PWM Delay Count bits(1)

Delay time, in number of FOSC/4 (4 * TOSC) cycles, between the scheduled and actual time for

a PWM signal to transition to active.

Note 1: Unimplemented on 28-pin devices; bits read ‘0’.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

CONTROL REGISTER

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1(1) PSSBD0(1)

bit 7 bit 0

bit 7 ECCPASE: ECCP Auto-Shutdown Event Status bit

1 = A shutdown event has occurred; ECCP outputs are in shutdown state

0 = ECCP outputs are operating

bit 6-4 ECCPAS<2:0>: ECCP Auto-Shutdown Source Select bits

111 = FLT0 or Comparator 1 or Comparator 2

110 = FLT0 or Comparator 2

101 = FLT0 or Comparator 1

100 =FLT0

011 = Either Comparator 1 or 2

010 = Comparator 2 output

001 = Comparator 1 output

000 = Auto-shutdown is disabled

bit 3-2 PSSAC<1:0>: Pins A and C Shutdown State Control bits

1x = Pins A and C are tri-state (40/44-pin devices);

PWM output is tri-state (28-pin devices)

01 = Drive Pins A and C to ‘1’

00 = Drive Pins A and C to ‘0’

bit 1-0 PSSBD<1:0>: Pins B and D Shutdown State Control bits(1)

1x = Pins B and D tri-state

01 = Drive Pins B and D to ‘1’

00 = Drive Pins B and D to ‘0’

Note 1: Unimplemented on 28-pin devices; bits read as ‘0’.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

17.4.7.1 Auto-Shutdown and

Automatic Restart

The auto-shutdown feature can be configured to allow

automatic restarts of the module following a shutdown

event. This is enabled by setting the PRSEN bit of the

ECCP1DEL register (ECCP1DEL<7>).

In Shutdown mode with PRSEN = 1 (Figure 17-10), the

ECCPASE bit will remain set for as long as the cause

of the shutdown continues. When the shutdown condi-

tion clears, the ECCP1ASE bit is cleared. If PRSEN = 0

(Figure 17-11), once a shutdown condition occurs, the

ECCPASE bit will remain set until it is cleared by

firmware. Once ECCPASE is cleared, the Enhanced

PWM will resume at the beginning of the next PWM

period.

Independent of the PRSEN bit setting, if the auto-

shutdown source is one of the comparators, the

shutdown condition is a level. The ECCPASE bit

cannot be cleared as long as the cause of the shutdown

persists.

The Auto-Shutdown mode can be forced by writing a ‘1’

to the ECCPASE bit.

17.4.8 START-UP CONSIDERATIONS

When the ECCP module is used in the PWM mode, the

application hardware must use the proper external pull-

up and/or pull-down resistors on the PWM output pins.

When the microcontroller is released from Reset, all of

the I/O pins are in the high-impedance state. The

external circuits must keep the power switch devices in

the OFF state until the microcontroller drives the I/O

pins with the proper signal levels, or activates the PWM

output(s).

The CCP1M<1:0> bits (CCP1CON<1:0>) allow the

user to choose whether the PWM output signals are

active-high or active-low for each pair of PWM output

pins (P1A/P1C and P1B/P1D). The PWM output

polarities must be selected before the PWM pins are

configured as outputs. Changing the polarity configura-

tion while the PWM pins are configured as outputs is

not recommended, since it may result in damage to the

application circuits.

The P1A, P1B, P1C and P1D output latches may not be

in the proper states when the PWM module is initialized.

Enabling the PWM pins for output at the same time as

the ECCP module may cause damage to the applica-

tion circuit. The ECCP module must be enabled in the

proper output mode and complete a full PWM cycle

before configuring the PWM pins as outputs. The com-

pletion of a full PWM cycle is indicated by the TMR2IF

bit being set as the second PWM period begins.

FIGURE 17-10: PWM AUTO-SHUTDOWN (PRSEN = 1, AUTO-RESTART ENABLED)

FIGURE 17-11: PWM AUTO-SHUTDOWN (PRSEN = 0, AUTO-RESTART DISABLED)

Note: Writing to the ECCPASE bit is disabled

while a shutdown condition is active.

Shutdown

PWM

ECCPASE bit

Activity

Event

PWM Period PWM Period PWM Period

Duty Cycle

Dead Time

Duty Cycle

Dead TimeDead Time

Duty Cycle

Shutdown

PWM

ECCPASE bit

Activity

Event

PWM Period PWM Period PWM Period

ECCPASE

Cleared by Firmware

Duty Cycle

Dead Time

Duty Cycle Duty Cycle

Dead TimeDead Time

PIC18F2221/2321/4221/4321 FAMILY

17.4.9 SETUP FOR PWM OPERATION

The following steps should be taken when configuring

the ECCP module for PWM operation:

1. Configure the PWM pins, P1A and P1B (and

P1C and P1D, if used), as inputs by setting the

corresponding TRIS bits.

2. Set the PWM period by loading the PR2 register.

3. If auto-shutdown is required, do the following:

• Disable auto-shutdown (ECCPASE = 0)

• Configure source (FLT0, Comparator 1 or

Comparator 2)

• Wait for non-shutdown condition

4. Configure the ECCP module for the desired

PWM mode and configuration by loading the

CCP1CON register with the appropriate values:

• Select one of the available output

configurations and direction with the P1M<1:0

bits.

• Select the polarities of the PWM output

signals with the CCP1M<3:0> bits.

5. Set the PWM duty cycle by loading the CCPR1L

6. For Half-Bridge Output mode, set the dead-

band delay by loading ECCP1DEL<6:0> with

the appropriate value.

7. If auto-shutdown operation is required, load the

ECCP1AS register:

• Select the auto-shutdown sources using the

ECCPAS<2:0> bits.

• Select the shutdown states of the PWM

output pins using the PSSAC<1:0> and

PSSBD<1:0> bits.

• Set the ECCPASE bit (ECCP1AS<7>).

• Configure the comparators using the CMCON

• Configure the comparator inputs as analog

inputs.

8. If auto-restart operation is required, set the

PRSEN bit (ECCP1DEL<7>).

9. Configure and start TMR2:

• Clear the TMR2 interrupt flag bit by clearing

the TMR2IF bit (PIR1<1>).

• Set the TMR2 prescale value by loading the

T2CKPS bits (T2CON<1:0>).

• Enable Timer2 by setting the TMR2ON bit

(T2CON<2>).

10. Enable PWM outputs after a new PWM cycle

has started:

• Wait until TMRx overflows (TMRxIF bit is set).

• Enable the CCP1/P1A, P1B, P1C and/or P1D

pin outputs by clearing the respective TRIS

bits.

• Clear the ECCPASE bit (ECCP1AS<7>).

17.4.10 OPERATION IN POWER-MANAGED

MODES

In Sleep mode, all clock sources are disabled. Timer2

will not increment and the state of the module will not

change. If the ECCP pin is driving a value, it will continue

to drive that value. When the device wakes up, it will

continue from this state. If Two-Speed Start-ups are

enabled, the initial start-up frequency from INTOSC and

the postscaler may not be stable immediately.

In PRI_IDLE mode, the primary clock will continue to

clock the ECCP module without change. In all other

power-managed modes, the selected power-managed

mode clock will clock Timer2. Other power-managed

mode clocks will most likely be different than the

primary clock frequency.

17.4.10.1 Operation with Fail-Safe

Clock Monitor

If the Fail-Safe Clock Monitor is enabled, a clock failure

will force the device into the power-managed RC_RUN

mode and the OSCFIF bit (PIR2<7>) will be set. The

ECCP will then be clocked from the internal oscillator

clock source, which may have a different clock

frequency than the primary clock.

See the previous section for additional details.

17.4.11 EFFECTS OF A RESET

Both Power-on Reset and subsequent Resets will force

all ports to Input mode and the CCP registers to their

Reset states.

This forces the Enhanced CCP module to reset to a

state compatible with the standard CCP module.

PIC18F2221/2321/4221/4321 FAMILY

TABLE 17-3: REGISTERS ASSOCIATED WITH ECCP1 MODULE AND TIMER1 TO TIMER3

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

RCON IPEN SBOREN(1) —RI TO PD POR BOR 54

PIR1 PSPIF(2) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(2) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(2) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

PIR2 OSCFIF CMIF —EEIF BCLIF HLVDIF TMR3IF CCP2IF 58

PIE2 OSCFIE CMIE —EEIE BCLIE HLVDIE TMR3IE CCP2IE 58

IPR2 OSCFIP CMIP —EEIP BCLIP HLVDIP TMR3IP CCP2IP 58

TRISB PORTB Data Direction Register 58

TRISC PORTC Data Direction Register 58

TRISD(2) PORTD Data Direction Register 58

TMR1L Timer1 Register Low Byte 56

TMR1H Timer1 Register High Byte 56

T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 56

TMR2 Timer2 Register 56

T2CON — T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 56

PR2 Timer2 Period Register 56

TMR3L Timer3 Register Low Byte 57

TMR3H Timer3 Register High Byte 57

T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 57

CCPR1L Capture/Compare/PWM Register 1 Low Byte 57

CCPR1H Capture/Compare/PWM Register 1 High Byte 57

CCP1CON P1M1(2) P1M0(2) DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 57

ECCP1AS ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1(2) PSSBD0(2) 57

ECCP1DEL PRSEN PDC6(2) PDC5(2) PDC4(2) PDC3(2) PDC2(2) PDC1(2) PDC0(2) 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used during ECCP operation.

Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled and

reads as ‘0’. See Section 5.4 “Brown-out Reset (BOR)”.

2: These registers and/or bits are unimplemented on 28-pin devices; always maintain these bits clear.

PIC18F2221/2321/4221/4321 FAMILY

18.0 MASTER SYNCHRONOUS

SERIAL PORT (MSSP)

MODULE

18.1 Master SSP (MSSP) Module

Overview

The Master Synchronous Serial Port (MSSP) module is

a serial interface, useful for communicating with other

peripheral or microcontroller devices. These peripheral

devices may be serial EEPROMs, shift registers,

display drivers, A/D converters, etc. The MSSP module

can operate in one of two modes:

• Serial Peripheral Interface (SPI)

• Inter-Integrated Circuit (I2C™)

- Full Master mode

- Slave mode (with address masking for both

10-bit and 7-bit addressing)

The I2C interface supports the following modes in

hardware:

•Master mode

• Multi-Master mode

• Slave mode

18.2 Control Registers

The MSSP module has three associated registers.

These include a status register (SSPSTAT) and two

control registers (SSPCON1 and SSPCON2). The use

of these registers and their individual Configuration bits

differ significantly depending on whether the MSSP

module is operated in SPI or I2C mode.

Additional details are provided under the individual

sections.

18.3 SPI Mode

The SPI mode allows 8 bits of data to be synchronously

transmitted and received simultaneously. All four SPI

modes are supported. To accomplish communication,

typically three pins are used:

• Serial Data Out (SDO) – SDO

• Serial Data In (SDI) – SDI/SDA

• Serial Clock (SCK) – SCK/SCL

Additionally, a fourth pin may be used when in a Slave

mode of operation:

• Slave Select (SS)

Figure 18-1 shows the block diagram of the MSSP

module when operating in SPI mode.

FIGURE 18-1: MSSP BLOCK DIAGRAM

(SPI MODE)

( )

Read Write

Internal

Data Bus

SSPSR reg

SSPM<3:0>

bit 0 Shift

Clock

SS Control

Enable

Edge

Select

Clock Select

TMR2 Output

TOSC

Prescaler

4, 16, 64

Edge

Select

Data to TX/RX in SSPSR

TRIS bit

SMP:CKE

SDO

SSPBUF reg

SDI/SDA

SCK/SCL

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18.3.1 REGISTERS

The MSSP module has four registers for SPI mode

operation. These are:

• MSSP Control Register 1 (SSPCON1)

• MSSP Status Register (SSPSTAT)

• Serial Receive/Transmit Buffer Register

(SSPBUF)

• MSSP Shift Register (SSPSR) – Not directly

accessible

SSPCON1 and SSPSTAT are the control and status

registers in SPI mode operation. The SSPCON1 register

is readable and writable. The lower 6 bits of the

SSPSTAT are read-only. The upper two bits of the

SSPSTAT are read/write.

SSPSR is the shift register used for shifting data in or

out. SSPBUF is the buffer register to which data bytes

are written to or read from.

In receive operations, SSPSR and SSPBUF together

create a double-buffered receiver. When SSPSR

receives a complete byte, it is transferred to SSPBUF

and the SSPIF interrupt is set.

During transmission, the SSPBUF is not double-

buffered. A write to SSPBUF will write to both SSPBUF

and SSPSR.

R/W-0 R/W-0 R-0 R-0 R-0 R-0 R-0 R-0

SMP CKE D/A PSR/WUA BF

bit 7 bit 0

bit 7 SMP: Sample bit

SPI Master mode:

1 = Input data sampled at end of data output time

0 = Input data sampled at middle of data output time

SPI Slave mode:

SMP must be cleared when SPI is used in Slave mode.

bit 6 CKE: SPI Clock Select bit

1 = Transmit occurs on transition from active to Idle clock state

0 = Transmit occurs on transition from Idle to active clock state

Note: Polarity of clock state is set by the CKP bit (SSPCON1<4>).

bit 5 D/A: Data/Address bit

Used in I2C™ mode only.

bit 4 P: Stop bit

Used in I2C mode only. This bit is cleared when the MSSP module is disabled, SSPEN is

cleared.

bit 3 S: Start bit

Used in I2C mode only.

bit 2 R/W: Read/Write Information bit

Used in I2C mode only.

bit 1 UA: Update Address bit

Used in I2C mode only.

bit 0 BF: Buffer Full Status bit (Receive mode only)

1 = Receive complete, SSPBUF is full

0 = Receive not complete, SSPBUF is empty

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

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R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0

bit 7 bit 0

bit 7 WCOL: Write Collision Detect bit (Transmit mode only)

1 = The SSPBUF register is written while it is still transmitting the previous word

(must be cleared in software)

0 = No collision

bit 6 SSPOV: Receive Overflow Indicator bit

SPI Slave mode:

1 = A new byte is received while the SSPBUF register is still holding the previous data. In case

of overflow, the data in SSPSR is lost. Overflow can only occur in Slave mode. The user

must read the SSPBUF, even if only transmitting data, to avoid setting overflow (must be

cleared in software).

0 = No overflow

Note: In Master mode, the overflow bit is not set since each new reception (and

transmission) is initiated by writing to the SSPBUF register.

bit 5 SSPEN: Synchronous Serial Port Enable bit

1 = Enables serial port and configures SCK, SDO, SDI and SS as serial port pins

0 = Disables serial port and configures these pins as I/O port pins

Note: When enabled, these pins must be properly configured as input or output.

bit 4 CKP: Clock Polarity Select bit

1 = Idle state for clock is a high level

0 = Idle state for clock is a low level

bit 3-0 SSPM<3:0>: Synchronous Serial Port Mode Select bits

0101 = SPI Slave mode, clock = SCK pin, SS pin control disabled, SS can be used as I/O pin

0100 = SPI Slave mode, clock = SCK pin, SS pin control enabled

0011 = SPI Master mode, clock = TMR2 output/2

0010 = SPI Master mode, clock = FOSC/64

0001 = SPI Master mode, clock = FOSC/16

0000 = SPI Master mode, clock = FOSC/4

Note: Bit combinations not specifically listed here are either reserved or implemented in

I2C™ mode only.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

18.3.2 OPERATION

When initializing the SPI, several options need to be

specified. This is done by programming the appropriate

control bits (SSPCON1<5:0> and SSPSTAT<7:6>).

These control bits allow the following to be specified:

• Master mode (SCK is the clock output)

• Slave mode (SCK is the clock input)

• Clock Polarity (Idle state of SCK)

• Data Input Sample Phase (middle or end of data

output time)

• Clock Edge (output data on rising/falling edge

of SCK)

• Clock Rate (Master mode only)

• Slave Select mode (Slave mode only)

The MSSP consists of a transmit/receive shift register

(SSPSR) and a buffer register (SSPBUF). The SSPSR

shifts the data in and out of the device, MSb first. The

SSPBUF holds the data that was written to the SSPSR

until the received data is ready. Once the 8 bits of data

have been received, that byte is moved to the SSPBUF

(SSPSTAT<0>), and the interrupt flag bit, SSPIF, are

set. This double-buffering of the received data

(SSPBUF) allows the next byte to start reception before

reading the data that was just received. Any write to the

SSPBUF register during transmission/reception of data

will be ignored and the write collision detect bit, WCOL

(SSPCON1<7>), will be set. User software must clear

the WCOL bit so that it can be determined if the following

write(s) to the SSPBUF register completed successfully.

When the application software is expecting to receive

valid data, the SSPBUF should be read before the next

byte of data to transfer is written to the SSPBUF. The

Buffer Full bit, BF (SSPSTAT<0>), indicates when

SSPBUF has been loaded with the received data

(transmission is complete). When the SSPBUF is read,

the BF bit is cleared. This data may be irrelevant if the

SPI is only a transmitter. Generally, the MSSP interrupt

is used to determine when the transmission/reception

has completed. The SSPBUF must be read and/or

written. If the interrupt method is not going to be used,

then software polling can be done to ensure that a write

collision does not occur. Example 18-1 shows the

loading of the SSPBUF (SSPSR) for data transmission.

The SSPSR is not directly readable or writable and can

only be accessed by addressing the SSPBUF register.

Additionally, the MSSP Status register (SSPSTAT)

indicates the various status conditions.

EXAMPLE 18-1: LOADING THE SSPBUF (SSPSR) REGISTER

Note: To avoid lost data in Master mode, a read of

the SSPBUF must be performed to clear the

Buffer Full (BF) detect bit (SSPSTAT<0>)

between each transmission.

Note: The SSPBUF register cannot be used with

read-modify-write instructions, such as

BCF, BTFSC and COMF, etc.

LOOP BTFSS SSPSTAT, BF ;Has data been received (transmit complete)?

BRA LOOP ;No

MOVF SSPBUF, W ;WREG reg = contents of SSPBUF

MOVWF RXDATA ;Save in user RAM, if data is meaningful

MOVF TXDATA, W ;W reg = contents of TXDATA

MOVWF SSPBUF ;New data to xmit

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18.3.3 ENABLING SPI I/O

To enable the serial port, MSSP Enable bit, SSPEN

(SSPCON1<5>), must be set. To reset or reconfigure

SPI mode, clear the SSPEN bit, reinitialize the

SSPCON registers and then set the SSPEN bit. This

configures the SDI, SDO, SCK and SS pins as serial

port pins. For the pins to behave as the serial port

function, some must have their data direction bits (in

the TRIS register) appropriately programmed as

follows:

• SDI is automatically controlled by the SPI module

• SDO must have TRISC<5> bit cleared

• SCK (Master mode) must have TRISC<3> bit

cleared

• SCK (Slave mode) must have TRISC<3> bit set

•SS

must have TRISA<5> bit set

Any serial port function that is not desired may be

overridden by programming the corresponding data

direction (TRIS) register to the opposite value.

18.3.4 TYPICAL CONNECTION

Figure 18-2 shows a typical connection between two

microcontrollers. The master controller (Processor 1)

initiates the data transfer by sending the SCK signal.

Data is shifted out of both shift registers on their pro-

grammed clock edge and latched on the opposite edge

of the clock. Both processors should be programmed to

the same Clock Polarity (CKP), then both controllers

would send and receive data at the same time.

Whether the data is meaningful (or dummy data)

depends on the application software. This leads to

three scenarios for data transmission:

• Master sends data – Slave sends dummy data

• Master sends data – Slave sends data

• Master sends dummy data – Slave sends data

FIGURE 18-2: SPI MASTER/SLAVE CONNECTION

Serial Input Buffer

(SSPBUF)

Shift Register

(SSPSR)

MSb LSb

SDO

SDI

PROCESSOR 1

SCK

SPI Master SSPM<3:0> = 00xxb

Serial Input Buffer

(SSPBUF)

Shift Register

(SSPSR)

LSb

MSb

SDI

SDO

PROCESSOR 2

SCK

SPI Slave SSPM<3:0> = 010xb

Serial Clock

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18.3.5 MASTER MODE

The master can initiate the data transfer at any time

because it controls the SCK. The master determines

when the slave (Processor 2, Figure 18-2) is to

broadcast data by the software protocol.

In Master mode, the data is transmitted/received as

soon as the SSPBUF register is written to. If the SPI

operation is only going to receive, the SDO output

could be disabled (programmed as an input). The

SSPSR register will continue to shift in the signal pres-

ent on the SDI pin at the programmed clock rate. As

each byte is received, it will be loaded into the SSPBUF

tus bits appropriately set). This could be useful in

receiver applications as a “Line Activity Monitor” mode.

The clock polarity is selected by appropriately

programming the CKP bit (SSPCON1<4>). This then,

would give waveforms for SPI communication as

shown in Figure 18-3, Figure 18-5 and Figure 18-6,

where the MSB is transmitted first. In Master mode, the

SPI clock rate (bit rate) is user-programmable to be one

of the following:

•F

OSC/4 (or TCY)

•FOSC/16 (or 4 • TCY)

•F

OSC/64 (or 16 • TCY)

• Timer2 output/2

This allows a maximum data rate (at 40 MHz) of

10.00 Mbps.

Figure 18-3 shows the waveforms for Master mode.

When the CKE bit is set, the SDO data is valid before

there is a clock edge on SCK. The change of the input

sample is shown based on the state of the SMP bit. The

time when the SSPBUF is loaded with the received

data is shown.

FIGURE 18-3: SPI MODE WAVEFORM (MASTER MODE)

SCK

(CKP = 0

SCK

(CKP = 1

SCK

(CKP = 0

SCK

(CKP = 1

4 Clock

Modes

Input

Sample

Input

Sample

SDI

bit 7 bit 0

SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

bit 7

SDI

SSPIF

(SMP = 1)

(SMP = 0)

(SMP = 1)

CKE = 1)

CKE = 0)

CKE = 1)

CKE = 0)

(SMP = 0)

Write to

SSPBUF

SSPSR to

SSPBUF

SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

(CKE = 0)

(CKE = 1)

Next Q4 Cycle

after Q2↓

bit 0

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18.3.6 SLAVE MODE

In Slave mode, the data is transmitted and received as

the external clock pulses appear on SCK. When the

last bit is latched, the SSPIF interrupt flag bit is set.

Before enabling the module in SPI Slave mode, the

clock line must match the proper Idle state. The clock

line can be observed by reading the SCK pin. The Idle

state is determined by the CKP bit (SSPCON1<4>).

While in Slave mode, the external clock is supplied by

the external clock source on the SCK pin. This external

clock must meet the minimum high and low times as

specified in the electrical specifications.

While in Sleep mode, the slave can transmit/receive

data. When a byte is received, the device will wake-up

from Sleep.

18.3.7 SLAVE SELECT

SYNCHRONIZATION

The SS pin allows a Synchronous Slave mode. The SPI

operation must be in Slave mode with the SS pin control

enabled (SSPCON1<3:0> = 04h). When the SS pin is

low, transmission and reception are enabled and the

SDO pin is driven. When the SS pin goes high, the SDO

pin is no longer driven, even if in the middle of a

transmitted byte and becomes a floating output. External

pull-up/pull-down resistors may be desirable depending

on the application.

When the SPI module resets, the bit counter is forced

to ‘0’. This can be done by either forcing the SS pin to

a high level or clearing the SSPEN bit.

To emulate two-wire communication, the SDO pin can

be connected to the SDI pin. When the SPI needs to

operate as a receiver, the SDO pin can be configured

as an input. This disables transmissions from the SDO.

The SDI can always be left as an input (SDI function)

since it cannot create a bus conflict.

FIGURE 18-4: SLAVE SYNCHRONIZATION WAVEFORM

Note 1: When the SPI interface is in Slave mode

with SS pin control enabled

(SSPCON1<3:0> = 0100), the SPI module

will reset if the SS pin is set to VDD.

2: If the SPI interface is used in Slave mode

with CKE set, then the SS pin control

must be enabled.

SCK

(CKP = 1

SCK

(CKP = 0

Input

Sample

SDI

bit 7

SDO bit 7 bit 6 bit 7

SSPIF

Interrupt

(SMP = 0)

CKE = 0)

(SMP = 0)

Write to

SSPBUF

SSPSR to

SSPBUF

Flag

bit 0

bit 7

bit 0

Next Q4 Cycle

after Q2↓

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FIGURE 18-5: SPI MODE WAVEFORM (SLAVE MODE WITH CKE = 0)

FIGURE 18-6: SPI MODE WAVEFORM (SLAVE MODE WITH CKE = 1)

SCK

(CKP = 1

SCK

(CKP = 0

Input

Sample

SDI

bit 7

SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

SSPIF

Interrupt

(SMP = 0)

CKE = 0)

(SMP = 0)

Write to

SSPBUF

SSPSR to

SSPBUF

Flag

Optional

Next Q4 Cycle

after Q2↓

bit 0

SCK

(CKP = 1

SCK

(CKP = 0

Input

Sample

SDI

bit 7 bit 0

SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

SSPIF

Interrupt

(SMP = 0)

CKE = 1)

(SMP = 0)

Write to

SSPBUF

SSPSR to

SSPBUF

Flag

Not Optional

Next Q4 Cycle

after Q2↓

PIC18F2221/2321/4221/4321 FAMILY

18.3.8 OPERATION IN POWER-MANAGED

MODES

In SPI Master mode, module clocks may be operating

at a different speed than when in full power mode. In

the case of Sleep mode, all clocks are halted.

In Idle modes, a clock is provided to the peripherals.

That clock should be from the primary clock source, the

secondary clock (Timer1 oscillator at 32.768 kHz) or

the INTOSC source. See Section 3.7 “Clock Sources

and Oscillator Switching” for additional information.

In most cases, the speed that the master clocks SPI

data is not important; however, this should be

evaluated for each system.

If MSSP interrupts are enabled, they can wake the

controller from Sleep mode, or one of the Idle modes,

when the master completes sending data. If an exit

from Sleep or Idle mode is not desired, MSSP

interrupts should be disabled.

If the Sleep mode is selected, all module clocks are

halted and the transmission/reception will remain in

that state until the devices wakes. After the device

returns to Run mode, the module will resume

transmitting and receiving data.

In SPI Slave mode, the SPI Transmit/Receive Shift

allows the device to be placed in any power-managed

mode and data to be shifted into the SPI Transmit/

Receive Shift register. When all 8 bits have been

received, the MSSP interrupt flag bit will be set and if

enabled, will wake the device.

18.3.9 EFFECTS OF A RESET

A Reset disables the MSSP module and terminates the

current transfer.

18.3.10 BUS MODE COMPATIBILITY

Table 18-1 shows the compatibility between the

standard SPI modes and the states of the CKP and

CKE control bits.

TABLE 18-1: SPI BUS MODES

There is also an SMP bit which controls when the data

is sampled.

TABLE 18-2: REGISTERS ASSOCIATED WITH SPI OPERATION

Standard SPI Mode

Terminology

Control Bits State

CKP CKE

0, 0 0 1

0, 1 0 0

1, 0 1 1

1, 1 1 0

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

TRISA TRISA7(2) TRISA6(2) PORTA Data Direction Control Register 58

TRISC PORTC Data Direction Control Register 58

SSPBUF MSSP Receive Buffer/Transmit Register 56

SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 56

SSPSTAT SMP CKE D/A P S R/W UA BF 56

Legend: Shaded cells are not used by the MSSP in SPI mode.

Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.

2: PORTA<7:6> and their direction bits are individually configured as port pins based on various primary

oscillator modes. When disabled, these bits read as ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

18.4 I2C Mode

The MSSP module in I2C mode fully implements all

master and slave functions (including general call

support) and provides interrupts on Start and Stop bits

in hardware to determine a free bus (multi-master

function). The MSSP module implements the standard

mode specifications, as well as 7-bit and 10-bit

addressing.

Two pins are used for data transfer:

• Serial clock (SCL) – RC3/SCK/SCL

• Serial data (SDA) – RC4/SDI/SDA

The user must configure these pins as inputs or outputs

through the TRISC<4:3> bits.

FIGURE 18-7: MSSP BLOCK DIAGRAM

(I2C™ MODE)

18.4.1 REGISTERS

The MSSP module has six registers for I2C operation.

These are:

• MSSP Control Register 1 (SSPCON1)

• MSSP Control Register 2 (SSPCON2)

• MSSP Status Register (SSPSTAT)

• Serial Receive/Transmit Buffer Register

(SSPBUF)

• MSSP Shift Register (SSPSR) – Not directly

accessible

• MSSP Address Register (SSPADD)

SSPCON1, SSPCON2 and SSPSTAT are the control

and status registers in I2C mode operation. The

SSPCON1 and SSPCON2 registers are readable and

writable. The lower 6 bits of the SSPSTAT are read-only.

The upper two bits of the SSPSTAT are read/write.

SSPSR is the shift register used for shifting data in or

out. SSPBUF is the buffer register to which data bytes

are written to or read from.

SSPADD register holds the slave device address when

the MSSP is configured in I2C Slave mode. When the

MSSP is configured in Master mode, the lower seven

bits of SSPADD act as the Baud Rate Generator reload

value.

In receive operations, SSPSR and SSPBUF together

create a double-buffered receiver. When SSPSR

receives a complete byte, it is transferred to SSPBUF

and the SSPIF interrupt is set.

During transmission, the SSPBUF is not double-

buffered. A write to SSPBUF will write to both SSPBUF

and SSPSR.

Read Write

SSPSR reg

Match Detect

SSPADD reg

Start and

Stop bit Detect

SSPBUF reg

Internal

Data Bus

Addr Match

Set, Reset

S, P bits

(SSPSTAT reg)

RC3/SCK/SCL

RC4/SDI/

Shift

Clock

MSb

SDA LSb

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R/W-0 R/W-0 R-0 R-0 R-0 R-0 R-0 R-0

SMP CKE D/A PSR/WUA BF

bit 7 bit 0

bit 7 SMP: Slew Rate Control bit

In Master or Slave mode:

1 = Slew rate control disabled for Standard Speed mode (100 kHz and 1 MHz)

0 = Slew rate control enabled for High-Speed mode (400 kHz)

bit 6 CKE: SMBus Select bit

In Master or Slave mode:

1 = Enable SMBus specific inputs

0 = Disable SMBus specific inputs

bit 5 D/A: Data/Address bit

In Master mode:

Reserved.

In Slave mode:

1 = Indicates that the last byte received or transmitted was data

0 = Indicates that the last byte received or transmitted was address

bit 4 P: Stop bit

1 = Indicates that a Stop bit has been detected last

0 = Stop bit was not detected last

Note: This bit is cleared on Reset and when SSPEN is cleared.

bit 3 S: Start bit

1 = Indicates that a Start bit has been detected last

0 = Start bit was not detected last

Note: This bit is cleared on Reset and when SSPEN is cleared.

bit 2 R/W: Read/Write Information bit (I2C™ mode only)

In Slave mode:

1 = Read

0 = Write

Note: This bit holds the R/W bit information following the last address match. This bit is

only valid from the address match to the next Start bit, Stop bit or not ACK bit.

In Master mode:

1 = Transmit is in progress

0 = Transmit is not in progress

Note: ORing this bit with SEN, RSEN, PEN, RCEN or ACKEN will indicate if the MSSP is

in Active mode.

bit 1 UA: Update Address bit (10-bit Slave mode only)

1 = Indicates that the user needs to update the address in the SSPADD register

0 = Address does not need to be updated

bit 0 BF: Buffer Full Status bit

In Transmit mode:

1 = SSPBUF is full

0 = SSPBUF is empty

In Receive mode:

1 = SSPBUF is full (does not include the ACK and Stop bits)

0 = SSPBUF is empty (does not include the ACK and Stop bits)

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0

bit 7 bit 0

bit 7 WCOL: Write Collision Detect bit

In Master Transmit mode:

1 = A write to the SSPBUF register was attempted while the I2C™ conditions were not valid for

a transmission to be started (must be cleared in software)

0 = No collision

In Slave Transmit mode:

1 = The SSPBUF register is written while it is still transmitting the previous word (must be

cleared in software)

0 = No collision

In Receive mode (Master or Slave modes):

This is a “don’t care” bit.

bit 6 SSPOV: Receive Overflow Indicator bit

In Receive mode:

1 = A byte is received while the SSPBUF register is still holding the previous byte (must be

cleared in software)

0 = No overflow

In Transmit mode:

This is a “don’t care” bit in Transmit mode.

bit 5 SSPEN: Master Synchronous Serial Port Enable bit

1 = Enables the serial port and configures the SDA and SCL pins as the serial port pins

0 = Disables serial port and configures these pins as I/O port pins

Note: When enabled, the SDA and SCL pins must be properly configured as inputs.

bit 4 CKP: SCK Release Control bit

In Slave mode:

1 = Release clock

0 = Holds clock low (clock stretch), used to ensure data setup time

In Master mode:

Unused in this mode.

bit 3-0 SSPM<3:0>: Master Synchronous Serial Port Mode Select bits

1111 = I2C Slave mode, 10-bit address with Start and Stop bit interrupts enabled

1110 = I2C Slave mode, 7-bit address with Start and Stop bit interrupts enabled

1011 = I2C Firmware Controlled Master mode (slave Idle)

1000 = I2C Master mode, clock = FOSC/(4 * (SSPADD + 1))

0111 = I2C Slave mode, 10-bit address

0110 = I2C Slave mode, 7-bit address

Bit combinations not specifically listed here are either reserved or implemented in SPI mode only.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

GCEN ACKSTAT ACKDT/

ADMSK5

ACKEN(1)/

ADMSK4

RCEN(1)/

ADMSK3

PEN(1)/

ADMSK2

RSEN(1)/

ADMSK1

SEN(1)

bit 7 bit 0

bit 7 GCEN: General Call Enable bit (Slave mode only)

1 = Enable interrupt when a general call address (0000h) is received in the SSPSR

0 = General call address disabled

bit 6 ACKSTAT: Acknowledge Status bit (Master Transmit mode only)

1 = Acknowledge was not received from slave

0 = Acknowledge was received from slave

bit 5 ACKDT/ADMSK5: Acknowledge Data bit

In Master Receive mode:

1 = Not Acknowledge

0 = Acknowledge

Note: Value that will be transmitted when the user initiates an Acknowledge sequence at

the end of a receive.

In Slave mode:

1 = Address masking of ADD5 enabled

0 = Address masking of ADD5 disabled

bit 4 ACKEN/ADMSK4: Acknowledge Sequence Enable bit

In Master Receive mode:(1)

1 = Initiate Acknowledge sequence on SDA and SCL pins and transmit ACKDT data bit.

Automatically cleared by hardware.

0 = Acknowledge sequence Idle

In Slave mode:

1 = Address masking of ADD4 enabled

0 = Address masking of ADD4 disabled

bit 3 RCEN/ADMSK3: Receive Enable bit

In Master Receive mode:(1)

1 = Enables Receive mode for I2C

0 = Receive Idle

In Slave mode:

1 = Address masking of ADD3 enabled

0 = Address masking of ADD3 disabled

bit 2 PEN/ADMSK2: Stop Condition Enable bit

In Master mode:(1)

1 = Initiate Stop condition on SDA and SCL pins. Automatically cleared by hardware.

0 = Stop condition Idle

In Slave mode:

1 = Address masking of ADD2 enabled

0 = Address masking of ADD2 disabled

bit 1 RSEN/ADMSK1: Repeated Start Condition Enable bit

In Master mode:(1)

1 = Initiate Repeated Start condition on SDA and SCL pins. Automatically cleared by hardware.

0 = Repeated Start condition Idle

In Slave mode (7-Bit Addressing mode):

1 = Address masking of ADD1 enabled

0 = Address masking of ADD1 disabled

In Slave mode (10-Bit Addressing mode):

1 = Address masking of ADD1 and ADD0 enabled

0 = Address masking of ADD1 and ADD0 disabled

PIC18F2221/2321/4221/4321 FAMILY

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

GCEN ACKSTAT ACKDT/

ADMSK5

ACKEN(1)/

ADMSK4

RCEN(1)/

ADMSK3

PEN(1)/

ADMSK2

RSEN(1)/

ADMSK1

SEN(1)

bit 7 bit 0

bit 0 SEN: Start Condition Enable/Stretch Enable bit(1)

In Master mode:

1 = Initiate Start condition on SDA and SCL pins. Automatically cleared by hardware.

0 = Start condition Idle

In Slave mode:

1 = Clock stretching is enabled for both slave transmit and slave receive (stretch enabled)

0 = Clock stretching is disabled

Note 1: For bits ACKEN, RCEN, PEN, RSEN, SEN: If the I2C module is active, these bits

may not be set (no spooling) and the SSPBUF may not be written (or writes to the

SSPBUF are disabled).

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

ADD7 ADD6 ADD5 ADD4 ADD3 ADD2 ADD1 ADD0

bit 7 bit 0

bit 7-0 ADD<7:0>: MSSP Address bits

Note 1: MSSP Address register in I2C Slave mode. MSSP Baud Rate register in I2C Master

mode.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

18.4.2 OPERATION

The MSSP module functions are enabled by setting

MSSP Enable bit, SSPEN (SSPCON1<5>).

The SSPCON1 register allows control of the I2C

operation. Four mode selection bits (SSPCON1<3:0>)

allow one of the following I2C modes to be selected:

•I

2C Master mode clock

•I

2C Slave mode (7-bit address)

•I

2C Slave mode (10-bit address)

•I

2C Slave mode (7-bit address) with Start and

Stop bit interrupts enabled

•I

2C Slave mode (10-bit address) with Start and

Stop bit interrupts enabled

•I

2C Firmware Controlled Master mode, slave is Idle

Selection of any I2C mode with the SSPEN bit set,

forces the SCL and SDA pins to be open-drain,

provided these pins are programmed to inputs by

setting the appropriate TRISC bits. To ensure proper

operation of the module, pull-up resistors must be

provided externally to the SCL and SDA pins.

18.4.3 SLAVE MODE

In Slave mode, the SCL and SDA pins must be config-

ured as inputs (TRISC<4:3> set). The MSSP module

will override the input state with the output data when

required (slave-transmitter).

The I2C Slave mode hardware will always generate an

interrupt on an address match. Address masking will

allow the hardware to generate an interrupt for more

than one address (up to 31 in 7-Bit Addressing mode

and up to 63 in 10-Bit Addressing mode). Through the

mode select bits, the user can also choose to interrupt

on Start and Stop bits

When an address is matched, or the data transfer after

an address match is received, the hardware auto-

matically will generate the Acknowledge (ACK) pulse

and load the SSPBUF register with the received value

currently in the SSPSR register.

Any combination of the following conditions will cause

the MSSP module not to give this ACK pulse:

• The Buffer Full bit, BF (SSPSTAT<0>), was set

before the transfer was received.

• The overflow bit, SSPOV (SSPCON1<6>), was

set before the transfer was received.

In this case, the SSPSR register value is not loaded

into the SSPBUF, but bit SSPIF (PIR1<3>) is set. The

BF bit is cleared by reading the SSPBUF register, while

bit SSPOV is cleared through software.

The SCL clock input must have a minimum high and

low for proper operation. The high and low times of the

I2C specification, as well as the requirement of the

MSSP module, are shown in timing parameter 100 and

parameter 101.

18.4.3.1 Addressing

Once the MSSP module has been enabled, it waits for

a Start condition to occur. Following the Start condition,

the 8 bits are shifted into the SSPSR register. All incom-

ing bits are sampled with the rising edge of the clock

(SCL) line. The value of register SSPSR<7:1> is

compared to the value of the SSPADD register. The

address is compared on the falling edge of the eighth

clock (SCL) pulse. If the addresses match and the BF

and SSPOV bits are clear, the following events occur:

1. The SSPSR register value is loaded into the

SSPBUF register.

2. The Buffer Full bit, BF, is set.

3. An ACK pulse is generated.

4. MSSP Interrupt Flag bit, SSPIF (PIR1<3>), is

set (interrupt is generated, if enabled) on the

falling edge of the ninth SCL pulse.

In 10-Bit Addressing mode, two address bytes need to

be received by the slave. The five Most Significant bits

(MSbs) of the first address byte specify if this is a 10-bit

address. Bit R/W (SSPSTAT<2>) must specify a write so

the slave device will receive the second address byte.

For a 10-bit address, the first byte would equal ‘11110

A9 A8 0’, where ‘A9’ and ‘A8’ are the two MSbs of the

address. The sequence of events for 10-bit address is as

follows, with steps 7 through 9 for the slave-transmitter:

1. Receive first (high) byte of address (bits SSPIF,

BF and UA (SSPSTAT<1>) are set).

2. Update the SSPADD register with second (low)

byte of address (clears bit UA and releases the

SCL line).

3. Read the SSPBUF register (clears bit BF) and

clear flag bit, SSPIF.

4. Receive second (low) byte of address (bits

SSPIF, BF and UA are set).

5. Update the SSPADD register with the first (high)

byte of address. If match releases SCL line, this

will clear bit UA.

6. Read the SSPBUF register (clears bit BF) and

clear flag bit, SSPIF.

7. Receive Repeated Start condition.

8. Receive first (high) byte of address (bits SSPIF

and BF are set).

9. Read the SSPBUF register (clears bit BF) and

clear flag bit, SSPIF.

PIC18F2221/2321/4221/4321 FAMILY

18.4.3.2 Address Masking

Masking an address bit causes that bit to become a

“don’t care”. When one address bit is masked, two

addresses will be Acknowledged and cause an inter-

rupt. It is possible to mask more than one address bit at

a time, which makes it possible to Acknowledge up to

31 addresses in 7-Bit Addressing mode and up to

63 addresses in 10-Bit Addressing mode (see

Example 18-2).

The I2C slave behaves the same way whether address

masking is used or not. However, when address mask-

ing is used, the I2C slave can Acknowledge multiple

addresses and cause interrupts. When this occurs, it is

necessary to determine which address caused the

interrupt by checking the SSPBUF register.

• 7-Bit Addressing mode

Address mask bits, ADMSK<5:1>, mask the corre-

sponding address bits in the SSPADD register. For any

ADMSK bits that are active (ADMSK<n> = 1), the

corresponding address bit is ignored (ADD<n> = x). For

the module to issue an address Acknowledge, it is

sufficient to match only on addresses that do not have an

active address mask.

• 10-Bit Addressing mode

Address mask bits, ADMSK<5:2>, mask the

corresponding address bits in the SSPADD register. In

addition, ADMSK<1> simultaneously masks the two

LSBs of the address, ADD<1:0>. For any ADMSK bits

that are active (ADMSK<n> = 1), the corresponding

address bit is ignored (ADD<n> = x). Also note that

although in 10-Bit Addressing mode, the upper address

bits reuse part of the SSPADD register bits, the address

mask bits do not interact with those bits. They only

affect the lower address bits.

EXAMPLE 18-2: ADDRESS MASKING

Note 1: ADMSK<1> masks the two Least

Significant bits of the address.

2: The two Most Significant bits of the

address are not affected by address

masking.

7-Bit Addressing mode:

SSPADD<7:1> = 1010 0000

ADMSK<5:1> = 00 111

Addresses Acknowledged = 0xA0, 0xA2, 0xA4, 0xA6, 0xA8, 0xAA, 0xAC, 0xAE

10-Bit Addressing mode:

SSPADD<7:0> = 1010 0000 (The two MSbs are ignored in this example since they are not affected)

ADMSK<5:1> = 00 111

Addresses Acknowledged = 0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8, 0xA9, 0xAA, 0xAB,

0xAC, 0xAD, 0xAE, 0xAF

The upper two bits are not affected by the address masking.

PIC18F2221/2321/4221/4321 FAMILY

18.4.3.3 Reception

When the R/W bit of the address byte is clear and an

address match occurs, the R/W bit of the SSPSTAT

the SSPBUF register and the SDA line is held low

(ACK).

When the address byte overflow condition exists, then

the no Acknowledge (ACK) pulse is given. An overflow

condition is defined as either bit BF (SSPSTAT<0>) is

set, or bit SSPOV (SSPCON1<6>) is set.

An MSSP interrupt is generated for each data transfer

byte. Flag bit, SSPIF (PIR1<3>), must be cleared in

software. The SSPSTAT register is used to determine

the status of the byte.

If SEN is enabled (SSPCON2<0> = 1), RC3/SCK/SCL

will be held low (clock stretch) following each data

transfer. The clock must be released by setting bit,

CKP (SSPCON1<4>). See Section 18.4.4 “Clock

Stretching” for more detail.

18.4.3.4 Transmission

When the R/W bit of the incoming address byte is set

and an address match occurs, the R/W bit of the

SSPSTAT register is set. The received address is

loaded into the SSPBUF register. The ACK pulse will

be sent on the ninth bit and pin RC3/SCK/SCL is held

low regardless of SEN (see Section 18.4.4 “Clock

Stretching” for more detail). By stretching the clock,

the master will be unable to assert another clock pulse

until the slave is done preparing the transmit data. The

transmit data must be loaded into the SSPBUF register

which also loads the SSPSR register. Then pin RC3/

SCK/SCL should be enabled by setting bit, CKP

(SSPCON1<4>). The eight data bits are shifted out on

the falling edge of the SCL input. This ensures that the

SDA signal is valid during the SCL high time

(Figure 18-10).

The ACK pulse from the master-receiver is latched on

the rising edge of the ninth SCL input pulse. If the SDA

line is high (not ACK), then the data transfer is

complete. In this case, when the ACK is latched by the

slave, the slave logic is reset and the slave monitors for

another occurrence of the Start bit. If the SDA line was

low (ACK), the next transmit data must be loaded into

the SSPBUF register. Again, pin RC3/SCK/SCL must

be enabled by setting bit CKP.

An MSSP interrupt is generated for each data transfer

byte. The SSPIF bit must be cleared in software and

the SSPSTAT register is used to determine the status

of the byte. The SSPIF bit is set on the falling edge of

the ninth clock pulse.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 18-8: I2C™ SLAVE MODE TIMING WITH SEN = 0 (RECEPTION, 7-BIT ADDRESSING)

SDA

SCL

SSPIF (PIR1<3>)

BF (SSPSTAT<0>)

SSPOV (SSPCON1<6>)

S1 234 56 7 89 1 2 34 5 67 89 1 2345 7 89 P

A7 A6 A5 A4 A3 A2 A1 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D1 D0

ACK

Receiving Data

ACK

Receiving Data

R/W = 0

ACK

Receiving Address

Cleared in software

SSPBUF is read

Bus master

terminates

transfer

SSPOV is set

because SSPBUF is

still full. ACK is not sent.

CKP (CKP does not reset to ‘0’ when SEN = 0)

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 18-9: I2C™ SLAVE MODE TIMING WITH SEN = 0 AND ADMSK<5:1> = 01011

(RECEPTION, 7-BIT ADDRESSING)

SDA

SCL

SSPIF (PIR1<3>)

BF (SSPSTAT<0>)

SSPOV (SSPCON1<6>)

S12345678912345678912345 789 P

A7 A6 A5 X A3 X X D7D6D5D4D3D2D1 D0 D7D6D5D4D3 D1D0

ACK

Receiving Data

ACK

Receiving Data

R/W = 0

ACK

Receiving Address

Cleared in software

SSPBUF is read

Bus master

terminates

transfer

SSPOV is set

because SSPBUF is

still full. ACK is not sent.

CKP

(CKP does not reset to ‘0’ when SEN = 0)

Note 1: x = Don’t care (i.e., address bit can be either a ‘1’ or a ‘0’).

2: In this example, an address equal to A7.A6.A5.X.A3.X.X will be Acknowledged and cause an interrupt.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 18-10: I2C™ SLAVE MODE TIMING (TRANSMISSION, 7-BIT ADDRESSING)

SDA

SCL

SSPIF (PIR1<3>)

BF (SSPSTAT<0>)

A6 A5 A4 A3 A2 A1 D6 D5 D4 D3 D2 D1 D0

1 2 3 4 5 6 7 8 2 3 4 5 6 7 8 9

SSPBUF is written in software

Cleared in software

Data in

sampled

ACK

Transmitting Data

R/W =

ACK

Receiving Address

A7 D7

9 1

D6 D5 D4 D3 D2 D1 D0

2 3 4 5 6 7 8 9

SSPBUF is written in software

Cleared in software

From SSPIF ISR

Transmitting Data

CKP

ACK

CKP is set in software CKP is set in software

SCL held low

while CPU

responds to SSPIF

Clear by reading

From SSPIF ISR

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 18-11: I2C™ SLAVE MODE TIMING WITH SEN = 0 AND ADMSK = 01001

(RECEPTION, 10-BIT ADDRESSING)

SDA

SCL

SSPIF (PIR1<3>)

BF (SSPSTAT<0>)

S123456789 123456789 12345 789 P

1 1 1 1 0 A9 A8 A7 A6 A5 X A3 A2 X X D7 D6 D5 D4 D3 D1 D0

Receive Data Byte

ACK

R/W = 0

ACK

Receive First Byte of Address

Cleared in software

Receive Second Byte of Address

Cleared by hardware

when SSPADD is updated

with low byte of address

UA (SSPSTAT<1>)

Clock is held low until

update of SSPADD has

taken place

UA is set indicating that

the SSPADD needs to be

updated

UA is set indicating that

SSPADD needs to be

updated

Cleared by hardware when

SSPADD is updated with high

byte of address

SSPBUF is written with

contents of SSPSR

Dummy read of SSPBUF

to clear BF flag

ACK

CKP

12345 789

D7 D6 D5 D4 D3 D1 D0

Receive Data Byte

Bus master

terminates

transfer

ACK

Cleared in software Cleared in software

SSPOV (SSPCON1<6>)

SSPOV is set

because SSPBUF is

still full. ACK is not sent.

(CKP does not reset to ‘0’ when SEN = 0)

Clock is held low until

update of SSPADD has

taken place

Note 1: x = Don’t care (i.e., address bit can be either a ‘1’ or a ‘0’).

2: In this example, an address equal to A9.A8.A7.A6.A5.X.A3.A2.X.X will be Acknowledged and cause an interrupt.

3: Note that the Most Significant bits of the address are not affected by the bit masking.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 18-12: I2C™ SLAVE MODE TIMING WITH SEN = 0 (RECEPTION, 10-BIT ADDRESSING)

SDA

SCL

SSPIF (PIR1<3>)

BF (SSPSTAT<0>)

S123456789 123456789 12345 789 P

1 1 1 1 0 A9 A8 A7 A6A5 A4A3A2A1 A0 D7 D6D5D4D3 D1D0

Receive Data Byte

ACK

R/W = 0

ACK

Receive First Byte of Address

Cleared in software

Receive Second Byte of Address

Cleared by hardware

when SSPADD is updated

with low byte of address

UA (SSPSTAT<1>)

Clock is held low until

update of SSPADD has

taken place

UA is set indicating that

the SSPADD needs to be

updated

UA is set indicating that

SSPADD needs to be

updated

Cleared by hardware when

SSPADD is updated with high

byte of address

SSPBUF is written with

contents of SSPSR

Dummy read of SSPBUF

to clear BF flag

ACK

CKP

12345 789

D7 D6 D5 D4 D3 D1 D0

Receive Data Byte

Bus master

terminates

transfer

ACK

Cleared in software Cleared in software

SSPOV (SSPCON1<6>)

SSPOV is set

because SSPBUF is

still full. ACK is not sent.

(CKP does not reset to ‘0’ when SEN = 0)

Clock is held low until

update of SSPADD has

taken place

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 18-13: I2C™ SLAVE MODE TIMING (TRANSMISSION, 10-BIT ADDRESSING)

SDA

SCL

SSPIF (PIR1<3>)

BF (SSPSTAT<0>)

S1234 5 6789 1 2345 678 9 12345 7 89 P

1 1 1 1 0 A9A8 A7 A6A5A4A3A2A1 A0 1 1 1 1 0 A8

R/W=1

ACK

R/W = 0

ACK

Receive First Byte of Address

Cleared in software

Bus master

terminates

transfer

Receive Second Byte of Address

Cleared by hardware when

SSPADD is updated with low

byte of address

UA (SSPSTAT<1>)

Clock is held low until

update of SSPADD has

taken place

UA is set indicating that

the SSPADD needs to be

updated

UA is set indicating that

SSPADD needs to be

updated

Cleared by hardware when

SSPADD is updated with high

byte of address.

SSPBUF is written with

contents of SSPSR

Dummy read of SSPBUF

to clear BF flag

Receive First Byte of Address

12345 789

D7 D6 D5 D4 D3 D1

ACK

Transmitting Data Byte

Dummy read of SSPBUF

to clear BF flag

Cleared in software

Write of SSPBUF

initiates transmit

Cleared in software

Completion of

clears BF flag

CKP (SSPCON1<4>)

CKP is set in software

CKP is automatically cleared in hardware, holding SCL low

Clock is held low until

update of SSPADD has

taken place

data transmission

Clock is held low until

CKP is set to ‘1’

third address sequence

BF flag is clear

at the end of the

PIC18F2221/2321/4221/4321 FAMILY

18.4.4 CLOCK STRETCHING

Both 7-Bit and 10-Bit Slave modes implement

automatic clock stretching during a transmit sequence.

The SEN bit (SSPCON2<0>) allows clock stretching to

be enabled during receives. Setting SEN will cause

the SCL pin to be held low at the end of each data

receive sequence.

18.4.4.1 Clock Stretching for 7-Bit Slave

Receive Mode (SEN = 1)

In 7-Bit Slave Receive mode, on the falling edge of the

ninth clock at the end of the ACK sequence if the BF

bit is set, the CKP bit in the SSPCON1 register is

automatically cleared, forcing the SCL output to be

held low. The CKP bit being cleared to ‘0’ will assert

the SCL line low. The CKP bit must be set in the user’s

ISR before reception is allowed to continue. By holding

the SCL line low, the user has time to service the ISR

and read the contents of the SSPBUF before the

master device can initiate another receive sequence.

This will prevent buffer overruns from occurring (see

Figure 18-15).

18.4.4.2 Clock Stretching for 10-Bit Slave

Receive Mode (SEN = 1)

In 10-Bit Slave Receive mode during the address

sequence, clock stretching automatically takes place

but CKP is not cleared. During this time, if the UA bit is

set after the ninth clock, clock stretching is initiated.

The UA bit is set after receiving the upper byte of the

10-bit address and following the receive of the second

byte of the 10-bit address with the R/W bit cleared to

‘0’. The release of the clock line occurs upon updating

SSPADD. Clock stretching will occur on each data

receive sequence as described in 7-bit mode.

18.4.4.3 Clock Stretching for 7-Bit Slave

Transmit Mode

7-Bit Slave Transmit mode implements clock stretch-

ing by clearing the CKP bit after the falling edge of the

ninth clock if the BF bit is clear. This occurs regardless

of the state of the SEN bit.

The user’s ISR must set the CKP bit before transmis-

sion is allowed to continue. By holding the SCL line

low, the user has time to service the ISR and load the

contents of the SSPBUF before the master device can

initiate another transmit sequence (see Figure 18-10).

18.4.4.4 Clock Stretching for 10-Bit Slave

Transmit Mode

In 10-Bit Slave Transmit mode, clock stretching is

controlled during the first two address sequences by

the state of the UA bit, just as it is in 10-Bit Slave

Receive mode. The first two addresses are followed

by a third address sequence which contains the high-

order bits of the 10-bit address and the R/W bit set to

‘1’. After the third address sequence is performed, the

UA bit is not set, the module is now configured in

Transmit mode and clock stretching is controlled by

the BF flag as in 7-Bit Slave Transmit mode (see

Figure 18-13).

Note 1: If the user reads the contents of the

SSPBUF before the falling edge of the

ninth clock, thus clearing the BF bit, the

CKP bit will not be cleared and clock

stretching will not occur.

2: The CKP bit can be set in software

regardless of the state of the BF bit. The

user should be careful to clear the BF bit

in the ISR before the next receive

sequence in order to prevent an overflow

condition.

Note: If the user polls the UA bit and clears it by

updating the SSPADD register before the

falling edge of the ninth clock occurs and if

the user hasn’t cleared the BF bit by read-

ing the SSPBUF register before that time,

then the CKP bit will still NOT be asserted

low. Clock stretching on the basis of the

state of the BF bit only occurs during a

data sequence, not an address sequence.

Note 1: If the user loads the contents of SSPBUF,

setting the BF bit before the falling edge of

the ninth clock, the CKP bit will not be

cleared and clock stretching will not occur.

2: The CKP bit can be set in software

regardless of the state of the BF bit.

PIC18F2221/2321/4221/4321 FAMILY

18.4.4.5 Clock Synchronization and

the CKP bit

When the CKP bit is cleared, the SCL output is forced

to ‘0’. However, clearing the CKP bit will not assert the

SCL output low until the SCL output is already

sampled low. Therefore, the CKP bit will not assert the

SCL line until an external I2C master device has

already asserted the SCL line. The SCL output will

remain low until the CKP bit is set and all other

devices on the I2C bus have deasserted SCL. This

ensures that a write to the CKP bit will not violate the

minimum high time requirement for SCL (see

Figure 18-14).

FIGURE 18-14: CLOCK SYNCHRONIZATION TIMING

SDA

SCL

DX – 1DX

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

SSPCON

CKP

Master device

deasserts clock

Master device

asserts clock

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 18-15: I2C™ SLAVE MODE TIMING WITH SEN = 1 (RECEPTION, 7-BIT ADDRESSING)

SDA

SCL

SSPIF (PIR1<3>)

BF (SSPSTAT<0>)

SSPOV (SSPCON1<6>)

S1 234 56 7 89 1 2345 67 89 1 23 45 7 89 P

A7 A6 A5 A4 A3 A2 A1 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D1 D0

ACK

Receiving Data

ACK

Receiving Data

R/W = 0

ACK

Receiving Address

Cleared in software

SSPBUF is read

Bus master

terminates

transfer

SSPOV is set

because SSPBUF is

still full. ACK is not sent.

CKP

written

to ‘1’ in

If BF is cleared

prior to the falling

edge of the 9th clock,

CKP will not be reset

to ‘0’ and no clock

stretching will occur

software

Clock is held low until

CKP is set to ‘1’

Clock is not held low

because buffer full bit is

clear prior to falling edge

of 9th clock

Clock is not held low

because ACK =

BF is set after falling

edge of the 9th clock,

CKP is reset to ‘0’ and

clock stretching occurs

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 18-16: I2C™ SLAVE MODE TIMING WITH SEN = 1 (RECEPTION, 10-BIT ADDRESSING)

SDA

SCL

SSPIF (PIR1<3>)

BF (SSPSTAT<0>)

S123456789 123456789 12345 789 P

1 1 1 1 0 A9A8 A7 A6 A5A4A3A2A1 A0 D7D6D5D4D3 D1D0

Receive Data Byte

ACK

R/W = 0

ACK

Receive First Byte of Address

Cleared in software

Receive Second Byte of Address

Cleared by hardware when

SSPADD is updated with low

byte of address after falling edge

UA (SSPSTAT<1>)

Clock is held low until

update of SSPADD has

taken place

UA is set indicating that

the SSPADD needs to be

updated

UA is set indicating that

SSPADD needs to be

updated

Cleared by hardware when

SSPADD is updated with high

byte of address after falling edge

SSPBUF is written with

contents of SSPSR

Dummy read of SSPBUF

to clear BF flag

ACK

CKP

12345 789

D7 D6 D5 D4 D3 D1 D0

Receive Data Byte

Bus master

terminates

transfer

ACK

Cleared in software Cleared in software

SSPOV (SSPCON1<6>)

CKP written to

‘

’

Note: An update of the SSPADD register before

the falling edge of the ninth clock will have

no effect on UA and UA will remain set.

Note: An update of the SSPADD

edge of the ninth clock will

have no effect on UA and

UA will remain set.

in software

Clock is held low until

update of SSPADD has

taken place

of ninth clock

SSPOV is set

because SSPBUF is

still full. ACK is not sent.

Dummy read of SSPBUF

to clear BF flag

Clock is held low until

CKP is set to

‘

’

Clock is not held low

because ACK =

PIC18F2221/2321/4221/4321 FAMILY

18.4.5 GENERAL CALL ADDRESS

SUPPORT

The addressing procedure for the I2C bus is such that

the first byte after the Start condition usually

determines which device will be the slave addressed by

the master. The exception is the general call address

which can address all devices. When this address is

used, all devices should, in theory, respond with an

Acknowledge.

The general call address is one of eight addresses

reserved for specific purposes by the I2C protocol. It

consists of all ‘0’s with R/W = 0.

The general call address is recognized when the

General Call Enable bit, GCEN, is enabled

(SSPCON2<7> is set). Following a Start bit detect,

8 bits are shifted into the SSPSR and the address is

compared against the SSPADD. It is also compared to

the general call address and fixed in hardware.

If the general call address matches, the SSPSR is

transferred to the SSPBUF, the BF flag bit is set (eighth

bit) and on the falling edge of the ninth bit (ACK bit), the

SSPIF interrupt flag bit is set.

When the interrupt is serviced, the source for the

interrupt can be checked by reading the contents of the

SSPBUF. The value can be used to determine if the

address was device specific or a general call address.

In 10-bit mode, the SSPADD is required to be updated

for the second half of the address to match and the UA

bit (SSPSTAT<1>) is set. If the general call address is

sampled when the GCEN bit is set, while the slave is

configured in 10-Bit Addressing mode, then the second

half of the address is not necessary, the UA bit will not

be set and the slave will begin receiving data after the

Acknowledge (Figure 18-17).

FIGURE 18-17: SLAVE MODE GENERAL CALL ADDRESS SEQUENCE

(7 OR 10-BIT ADDRESSING MODE)

SDA

SCL

SSPIF

BF (SSPSTAT<0>)

SSPOV (SSPCON1<6>)

Cleared in software

SSPBUF is read

R/W = 0

ACK

General Call Address

Address is compared to General Call Address

GCEN (SSPCON2<7>)

Receiving Data ACK

123456789123456789

D7 D6 D5 D4 D3 D2 D1 D0

after ACK, set interrupt

‘0’

‘1’

PIC18F2221/2321/4221/4321 FAMILY

18.4.6 MASTER MODE

Master mode is enabled by setting and clearing the

appropriate SSPM bits in SSPCON1 and by setting the

SSPEN bit. In Master mode, the SCL and SDA lines

are manipulated by the MSSP hardware.

Master mode of operation is supported by interrupt

generation on the detection of the Start and Stop

conditions. The Stop (P) and Start (S) bits are cleared

from a Reset or when the MSSP module is disabled.

Control of the I2C bus may be taken when the P bit is

set, or the bus is Idle, with both the S and P bits clear.

In Firmware Controlled Master mode, user code

conducts all I2C bus operations based on Start and

Stop bit conditions.

Once Master mode is enabled, the user has six

options.

1. Assert a Start condition on SDA and SCL.

2. Assert a Repeated Start condition on SDA and

SCL.

3. Write to the SSPBUF register initiating

transmission of data/address.

4. Configure the I2C port to receive data.

5. Generate an Acknowledge condition at the end

of a received byte of data.

6. Generate a Stop condition on SDA and SCL.

The following events will cause the MSSP Interrupt

Flag bit, SSPIF, to be set (MSSP interrupt, if enabled):

• Start condition

• Stop condition

• Data transfer byte transmitted/received

• Acknowledge transmit

• Repeated Start

FIGURE 18-18: MSSP BLOCK DIAGRAM (I2C™ MASTER MODE)

Note: The MSSP module, when configured in

I2C Master mode, does not allow queueing

of events. For instance, the user is not

allowed to initiate a Start condition and

immediately write the SSPBUF register to

initiate transmission before the Start

condition is complete. In this case, the

SSPBUF will not be written to and the

WCOL bit will be set, indicating that a write

to the SSPBUF did not occur.

Read Write

SSPSR

Start bit, Stop bit,

SSPBUF

Internal

Data Bus

Set/Reset, S, P, WCOL (SSPSTAT);

Shift

Clock

MSb LSb

SDA

Acknowledge

Generate

Stop bit Detect

Write Collision Detect

Clock Arbitration

State Counter for

end of XMIT/RCV

SCL

SCL In

Bus Collision

SDA In

Receive Enable

Clock Cntl

Clock Arbitrate/WCOL Detect

(hold off clock source)

SSPADD<6:0>

Baud

Set SSPIF, BCLIF;

Reset ACKSTAT, PEN (SSPCON2)

Rate

Generator

SSPM<3:0>

Start bit Detect

PIC18F2221/2321/4221/4321 FAMILY

18.4.6.1 I2C Master Mode Operation

The master device generates all of the serial clock

pulses and the Start and Stop conditions. A transfer is

ended with a Stop condition or with a Repeated Start

condition. Since the Repeated Start condition is also

the beginning of the next serial transfer, the I2C bus will

not be released.

In Master Transmitter mode, serial data is output

through SDA, while SCL outputs the serial clock. The

first byte transmitted contains the slave address of the

receiving device (7 bits) and the Read/Write (R/W) bit.

In this case, the R/W bit will be logic ‘0’. Serial data is

transmitted 8 bits at a time. After each byte is transmit-

ted, an Acknowledge bit is received. Start and Stop

conditions are output to indicate the beginning and the

end of a serial transfer.

In Master Receive mode, the first byte transmitted

contains the slave address of the transmitting device

(7 bits) and the R/W bit. In this case, the R/W bit will be

logic ‘1’. Thus, the first byte transmitted is a 7-bit slave

address followed by a ‘1’ to indicate the receive bit.

Serial data is received via SDA, while SCL outputs the

serial clock. Serial data is received 8 bits at a time. After

each byte is received, an Acknowledge bit is transmit-

ted. Start and Stop conditions indicate the beginning

and end of transmission.

The Baud Rate Generator used for the SPI mode

operation is used to set the SCL clock frequency for

either 100 kHz, 400 kHz or 1 MHz I2C operation. See

Section 18.4.7 “Baud Rate” for more detail.

A typical transmit sequence would go as follows:

1. The user generates a Start condition by setting

the Start Enable bit, SEN (SSPCON2<0>).

2. SSPIF is set. The MSSP module will wait the

required start time before any other operation

takes place.

3. The user loads the SSPBUF with the slave

address to transmit.

4. Address is shifted out the SDA pin until all 8 bits

are transmitted.

5. The MSSP module shifts in the ACK bit from the

slave device and writes its value into the

SSPCON2 register.

6. The MSSP module generates an interrupt at the

end of the ninth clock cycle by setting the SSPIF

bit.

7. The user loads the SSPBUF with eight bits of

data.

8. Data is shifted out the SDA pin until all 8 bits are

transmitted.

9. The MSSP module shifts in the ACK bit from the

slave device and writes its value into the

SSPCON2 register.

10. The MSSP module generates an interrupt at the

end of the ninth clock cycle by setting the SSPIF

bit.

11. The user generates a Stop condition by setting

the Stop Enable bit, PEN (SSPCON2<2>).

12. Interrupt is generated once the Stop condition is

complete.

PIC18F2221/2321/4221/4321 FAMILY

18.4.7 BAUD RATE

In I2C Master mode, the Baud Rate Generator (BRG)

reload value is placed in the lower 7 bits of the

SSPADD register (Figure 18-19). When a write occurs

to SSPBUF, the Baud Rate Generator will automatically

begin counting. The BRG counts down to 0 and stops

until another reload has taken place. The BRG count is

decremented twice per instruction cycle (T

CY) on the

Q2 and Q4 clocks. In I2C Master mode, the BRG is

reloaded automatically.

Once the given operation is complete (i.e., transmis-

sion of the last data bit is followed by ACK), the internal

clock will automatically stop counting and the SCL pin

will remain in its last state.

Table 18-3 demonstrates clock rates based on

instruction cycles and the BRG value loaded into

SSPADD.

FIGURE 18-19: BAUD RATE GENERATOR BLOCK DIAGRAM

TABLE 18-3: I2C™ CLOCK RATE W/BRG

Fosc FCY FCY * 2 BRG Value FSCL

(2 Rollovers of BRG)

40 MHz 10 MHz 20 MHz 18h 400 kHz

40 MHz 10 MHz 20 MHz 1Fh 312.5 kHz

40 MHz 10 MHz 20 MHz 63h 100 kHz

16 MHz 4 MHz 8 MHz 09h 400 kHz

16 MHz 4 MHz 8 MHz 0Ch 308 kHz

16 MHz 4 MHz 8 MHz 27h 100 kHz

4 MHz 1 MHz 2 MHz 02h 333 kHz

4 MHz 1 MHz 2 MHz 09h 100 kHz

4 MHz 1 MHz 2 MHz 00h 1 MHz

SSPM<3:0>

BRG Down Counter

CLKO FOSC/4

SSPADD<6:0>

SSPM<3:0>

SCL

Reload

Control

Reload

PIC18F2221/2321/4221/4321 FAMILY

18.4.7.1 Clock Arbitration

Clock arbitration occurs when the master, during any

receive, transmit or Repeated Start/Stop condition,

deasserts the SCL pin (SCL allowed to float high).

When the SCL pin is allowed to float high, the Baud

Rate Generator (BRG) is suspended from counting

until the SCL pin is actually sampled high. When the

SCL pin is sampled high, the Baud Rate Generator is

reloaded with the contents of SSPADD<6:0> and

begins counting. This ensures that the SCL high time

will always be at least one BRG rollover count in the

event that the clock is held low by an external device

(Figure 18-20).

FIGURE 18-20: BAUD RATE GENERATOR TIMING WITH CLOCK ARBITRATION

SDA

SCL

SCL deasserted but slave holds

DX – 1DX

BRG

SCL is sampled high, reload takes

place and BRG starts its count

03h 02h 01h 00h (hold off) 03h 02h

Reload

BRG

Value

SCL low (clock arbitration)

SCL allowed to transition high

BRG decrements on

Q2 and Q4 cycles

PIC18F2221/2321/4221/4321 FAMILY

18.4.8 I2C MASTER MODE START

CONDITION TIMING

To initiate a Start condition, the user sets the Start

Enable bit, SEN (SSPCON2<0>). If the SDA and SCL

pins are sampled high, the Baud Rate Generator is

reloaded with the contents of SSPADD<6:0> and starts

its count. If SCL and SDA are both sampled high when

the Baud Rate Generator times out (TBRG), the SDA

pin is driven low. The action of the SDA being driven

low while SCL is high is the Start condition and causes

the S bit (SSPSTAT<3>) to be set. Following this, the

Baud Rate Generator is reloaded with the contents of

SSPADD<6:0> and resumes its count. When the Baud

Rate Generator times out (TBRG), the SEN bit

(SSPCON2<0>) will be automatically cleared by

hardware; the Baud Rate Generator is suspended,

leaving the SDA line held low and the Start condition is

complete.

18.4.8.1 WCOL Status Flag

If the user writes the SSPBUF when a Start sequence

is in progress, the WCOL is set and the contents of the

buffer are unchanged (the write doesn’t occur).

FIGURE 18-21: FIRST START BIT TIMING

Note: If at the beginning of the Start condition,

the SDA and SCL pins are already sam-

pled low, or if during the Start condition, the

SCL line is sampled low before the SDA

line is driven low, a bus collision occurs,

the Bus Collision Interrupt Flag, BCLIF, is

set, the Start condition is aborted and the

I2C module is reset into its Idle state.

Note: Because queueing of events is not

allowed, writing to the lower 5 bits of

SSPCON2 is disabled until the Start

condition is complete.

SDA

SCL

TBRG

1st bit 2nd bit

TBRG

SDA = 1, At completion of Start bit,

SCL = 1

Write to SSPBUF occurs here

TBRG

hardware clears SEN bit

TBRG

Write to SEN bit occurs here Set S bit (SSPSTAT<3>)

and sets SSPIF bit

PIC18F2221/2321/4221/4321 FAMILY

18.4.9 I2C MASTER MODE REPEATED

START CONDITION TIMING

A Repeated Start condition occurs when the RSEN bit

(SSPCON2<1>) is programmed high and the I2C logic

module is in the Idle state. When the RSEN bit is set,

the SCL pin is asserted low. When the SCL pin is

sampled low, the Baud Rate Generator is loaded with

the contents of SSPADD<5:0> and begins counting.

The SDA pin is released (brought high) for one Baud

Rate Generator count (TBRG). When the Baud Rate

Generator times out, if SDA is sampled high, the SCL

pin will be deasserted (brought high). When SCL is

sampled high, the Baud Rate Generator is reloaded

with the contents of SSPADD<6:0> and begins count-

ing. SDA and SCL must be sampled high for one TBRG.

This action is then followed by assertion of the SDA pin

(SDA = 0) for one TBRG while SCL is high. Following

this, the RSEN bit (SSPCON2<1>) will be automatically

cleared and the Baud Rate Generator will not be

reloaded, leaving the SDA pin held low. As soon as a

Start condition is detected on the SDA and SCL pins,

the S bit (SSPSTAT<3>) will be set. The SSPIF bit will

not be set until the Baud Rate Generator has timed out.

Immediately following the SSPIF bit getting set, the user

may write the SSPBUF with the 7-bit address in 7-bit

mode, or the default first address in 10-bit mode. After

the first eight bits are transmitted and an ACK is

received, the user may then transmit an additional eight

bits of address (10-bit mode) or eight bits of data (7-bit

mode).

18.4.9.1 WCOL Status Flag

If the user writes the SSPBUF when a Repeated Start

sequence is in progress, the WCOL is set and the

contents of the buffer are unchanged (the write doesn’t

occur).

FIGURE 18-22: REPEATED START CONDITION WAVEFORM

Note 1: If RSEN is programmed while any other

event is in progress, it will not take effect.

2: A bus collision during the Repeated Start

condition occurs if:

• SDA is sampled low when SCL goes

from low-to-high.

• SCL goes low before SDA is

asserted low. This may indicate that

another master is attempting to

transmit a data ‘1’.

Note: Because queueing of events is not

allowed, writing of the lower 5 bits of

SSPCON2 is disabled until the Repeated

Start condition is complete.

SDA

SCL

Sr = Repeated Start

Write to SSPCON2

Write to SSPBUF occurs here

on falling edge of ninth clock,

end of Xmit

At completion of Start bit,

hardware clears RSEN bit

1st bit

S bit set by hardware

TBRG

SDA = 1,

SCL (no change).

SCL = 1

occurs here.

and sets SSPIF

RSEN bit set by hardware

TBRG TBRG TBRG

PIC18F2221/2321/4221/4321 FAMILY

18.4.10 I2C MASTER MODE TRANSMISSION

Transmission of a data byte, a 7-bit address or the

other half of a 10-bit address is accomplished by simply

writing a value to the SSPBUF register. This action will

set the Buffer Full flag bit, BF and allow the Baud Rate

Generator to begin counting and start the next

transmission. Each bit of address/data will be shifted

out onto the SDA pin after the falling edge of SCL is

asserted (see data hold time specification

parameter 106). SCL is held low for one Baud Rate

Generator rollover count (TBRG). Data should be valid

before SCL is released high (see data setup time

specification parameter 107). When the SCL pin is

released high, it is held that way for TBRG. The data on

the SDA pin must remain stable for that duration and

some hold time after the next falling edge of SCL. After

the eighth bit is shifted out (the falling edge of the eighth

clock), the BF flag is cleared and the master releases

SDA. This allows the slave device being addressed to

respond with an ACK bit during the ninth bit time if an

address match occurred, or if data was received

properly. The status of ACK is written into the ACKDT

bit on the falling edge of the ninth clock. If the master

receives an Acknowledge, the Acknowledge Status bit,

ACKSTAT, is cleared. If not, the bit is set. After the ninth

clock, the SSPIF bit is set and the master clock (Baud

Rate Generator) is suspended until the next data byte

is loaded into the SSPBUF, leaving SCL low and SDA

unchanged (Figure 18-23).

After the write to the SSPBUF, each bit of the address

will be shifted out on the falling edge of SCL until all

seven address bits and the R/W bit are completed. On

the falling edge of the eighth clock, the master will

deassert the SDA pin, allowing the slave to respond

with an Acknowledge. On the falling edge of the ninth

clock, the master will sample the SDA pin to see if the

address was recognized by a slave. The status of the

ACK bit is loaded into the ACKSTAT status bit

(SSPCON2<6>). Following the falling edge of the ninth

clock transmission of the address, the SSPIF is set, the

BF flag is cleared and the Baud Rate Generator is

turned off until another write to the SSPBUF takes

place, holding SCL low and allowing SDA to float.

18.4.10.1 BF Status Flag

In Transmit mode, the BF bit (SSPSTAT<0>) is set

when the CPU writes to SSPBUF and is cleared when

all 8 bits are shifted out.

18.4.10.2 WCOL Status Flag

If the user writes the SSPBUF when a transmit is

already in progress (i.e., SSPSR is still shifting out a

data byte), the WCOL flag is set and the contents of the

buffer are unchanged (the write doesn’t occur) after

2TCY after the SSPBUF write. If SSPBUF is rewritten

within 2 TCY, the WCOL bit is set and SSPBUF is

updated. This may result in a corrupted transfer. The

user should verify that the WCOL flag is clear after

each write to SSPBUF to ensure the transfer is correct.

18.4.10.3 ACKSTAT Status Flag

In Transmit mode, the ACKSTAT bit (SSPCON2<6>) is

cleared when the slave has sent an Acknowledge

(ACK =0) and is set when the slave does not Acknowl-

edge (ACK = 1). A slave sends an Acknowledge when

it has recognized its address (including a general call),

or when the slave has properly received its data.

18.4.11 I2C MASTER MODE RECEPTION

Master mode reception is enabled by programming the

Receive Enable bit, RCEN (SSPCON2<3>).

The Baud Rate Generator begins counting and on each

rollover, the state of the SCL pin changes (high-to-low/

low-to-high) and data is shifted into the SSPSR. After

the falling edge of the eighth clock, the receive enable

flag is automatically cleared, the contents of the

SSPSR are loaded into the SSPBUF, the BF flag bit is

set, the SSPIF flag bit is set and the Baud Rate Gener-

ator is suspended from counting, holding SCL low. The

MSSP is now in Idle state awaiting the next command.

When the buffer is read by the CPU, the BF flag bit is

automatically cleared. The user can then send an

Acknowledge bit at the end of reception by setting the

Acknowledge Sequence Enable bit, ACKEN

(SSPCON2<4>).

18.4.11.1 BF Status Flag

In receive operation, the BF bit is set when an address

or data byte is loaded into SSPBUF from SSPSR. It is

cleared when the SSPBUF register is read.

18.4.11.2 SSPOV Status Flag

In receive operation, the SSPOV bit is set when 8 bits

are received into the SSPSR and the BF flag bit is

already set from a previous reception.

18.4.11.3 WCOL Status Flag

If the user writes the SSPBUF when a receive is

already in progress (i.e., SSPSR is still shifting in a data

byte), the WCOL bit is set and the contents of the buffer

are unchanged (the write doesn’t occur).

Note: The MSSP module must be in an Idle state

before the RCEN bit is set or the RCEN bit

will be disregarded.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 18-23: I2C™ MASTER MODE WAVEFORM (TRANSMISSION, 7 OR 10-BIT ADDRESSING)

SDA

SCL

SSPIF

BF (SSPSTAT<0>)

SEN

A7 A6 A5 A4 A3 A2 A1 ACK = ‘0’ D7D6D5D4D3D2D1D0

ACK

Transmitting Data or Second Half

R/W = 0Transmit Address to Slave

123456789 123456789 P

Cleared in software service routine

SSPBUF is written in software

from MSSP interrupt

After Start condition, SEN cleared by hardware

SSPBUF written with 7-bit address and R/W,

start transmit

SCL held low

while CPU

responds to SSPIF

SEN = 0

of 10-bit Address

Write SSPCON2<0> SEN = 1

Start condition begins From slave, clear ACKSTAT bit SSPCON2<6>

ACKSTAT in

SSPCON2 = 1

Cleared in software

SSPBUF written

PEN

R/W

Cleared in software

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 18-24: I2C™ MASTER MODE WAVEFORM (RECEPTION, 7-BIT ADDRESSING)

D3D4

D6D7

A7 A6 A5 A4 A3 A2 A1

SDA

SCL 12

345678912345678 9 1234

Bus master

terminates

transfer

ACK

Receiving Data from Slave

D3D4

D6D7

ACK

R/W = 1

Transmit Address to Slave

SSPIF

ACK is not sent

Write to SSPCON2<0> (SEN = 1),

Write to SSPBUF occurs here, ACK from Slave

Master configured as a receiver

by programming SSPCON2<3> (RCEN = 1)

PEN bit = 1

written here

Data shifted in on falling edge of CLK

Cleared in software

start XMIT

SEN = 0

SSPOV

SDA = 0, SCL = 1

while CPU

(SSPSTAT<0>)

ACK

Cleared in software

Set SSPIF interrupt

at end of receive

Set P bit

(SSPSTAT<4>)

and SSPIF

Cleared in

software

ACK from Master

Set SSPIF at end

Set SSPIF interrupt

at end of Acknowledge

sequence

Set SSPIF interrupt

at end of Acknow-

ledge sequence

of receive

Set ACKEN, start Acknowledge sequence

SSPOV is set because

SSPBUF is still full

SDA = ACKDT = 1

RCEN cleared

automatically

RCEN = 1, start

next receive

Write to SSPCON2<4>

to start Acknowledge sequence

SDA = ACKDT (SSPCON2<5>) = 0

RCEN cleared

automatically

responds to SSPIF

ACKEN

begin Start condition

Cleared in software

SDA = ACKDT = 0

Last bit is shifted into SSPSR and

contents are unloaded into SSPBUF

PIC18F2221/2321/4221/4321 FAMILY

18.4.12 ACKNOWLEDGE SEQUENCE

TIMING

An Acknowledge sequence is enabled by setting the

Acknowledge Sequence Enable bit, ACKEN

(SSPCON2<4>). When this bit is set, the SCL pin is

pulled low and the contents of the Acknowledge data bit

are presented on the SDA pin. If the user wishes to gen-

erate an Acknowledge, then the ACKDT bit should be

cleared. If not, the user should set the ACKDT bit before

starting an Acknowledge sequence. The Baud Rate

Generator then counts for one rollover period (TBRG)

and the SCL pin is deasserted (pulled high). When the

SCL pin is sampled high (clock arbitration), the Baud

Rate Generator counts for TBRG. The SCL pin is then

pulled low. Following this, the ACKEN bit is automatically

cleared, the Baud Rate Generator is turned off and the

MSSP module then goes into Idle mode (Figure 18-25).

18.4.12.1 WCOL Status Flag

If the user writes the SSPBUF when an Acknowledge

sequence is in progress, then WCOL is set and the

contents of the buffer are unchanged (the write doesn’t

occur).

18.4.13 STOP CONDITION TIMING

A Stop bit is asserted on the SDA pin at the end of a

receive/transmit by setting the Stop Sequence Enable

bit, PEN (SSPCON2<2>). At the end of a receive/

transmit, the SCL line is held low after the falling edge

of the ninth clock. When the PEN bit is set, the master

will assert the SDA line low. When the SDA line is

sampled low, the Baud Rate Generator is reloaded and

counts down to 0. When the Baud Rate Generator

times out, the SCL pin will be brought high and one

TBRG (Baud Rate Generator rollover count) later, the

SDA pin will be deasserted. When the SDA pin is

sampled high while SCL is high, the P bit

(SSPSTAT<4>) is set. A TBRG later, the PEN bit is

cleared and the SSPIF bit is set (Figure 18-26).

18.4.13.1 WCOL Status Flag

If the user writes the SSPBUF when a Stop sequence

is in progress, then the WCOL bit is set and the

contents of the buffer are unchanged (the write doesn’t

occur).

FIGURE 18-25: ACKNOWLEDGE SEQUENCE WAVEFORM

FIGURE 18-26: STOP CONDITION RECEIVE OR TRANSMIT MODE

Note: TBRG = one Baud Rate Generator period.

SDA

SCL

SSPIF set at

Acknowledge sequence starts here,

write to SSPCON2 ACKEN automatically cleared

Cleared in

TBRG TBRG

the end of receive

ACKEN = 1, ACKDT = 0

SSPIF

software SSPIF set at the end

of Acknowledge sequence

Cleared in

software

ACK

SCL

SDA

SDA asserted low before rising edge of clock

Write to SSPCON2,

set PEN

Falling edge of

SCL = 1 for TBRG, followed by SDA = 1 for TBRG

9th clock

SCL brought high after TBRG

Note: TBRG = one Baud Rate Generator period.

TBRG TBRG

after SDA sampled high. P bit (SSPSTAT<4>) is set.

TBRG

to setup Stop condition

ACK

TBRG

PEN bit (SSPCON2<2>) is cleared by

hardware and the SSPIF bit is set

PIC18F2221/2321/4221/4321 FAMILY

18.4.14 SLEEP OPERATION

While in Sleep mode, the I2C module can receive

addresses or data and when an address match or

complete byte transfer occurs, wake the processor

from Sleep (if the MSSP interrupt is enabled).

18.4.15 EFFECTS OF A RESET

A Reset disables the MSSP module and terminates the

current transfer.

18.4.16 MULTI-MASTER MODE

In Multi-Master mode, the interrupt generation on the

detection of the Start and Stop conditions allows the

determination of when the bus is free. The Stop (P) and

Start (S) bits are cleared from a Reset or when the

MSSP module is disabled. Control of the I2C bus may

be taken when the P bit (SSPSTAT<4>) is set, or the

bus is Idle, with both the S and P bits clear. When the

bus is busy, enabling the MSSP interrupt will generate

the interrupt when the Stop condition occurs.

In multi-master operation, the SDA line must be

monitored for arbitration to see if the signal level is the

expected output level. This check is performed in

hardware with the result placed in the BCLIF bit.

The states where arbitration can be lost are:

• Address Transfer

• Data Transfer

• A Start Condition

• A Repeated Start Condition

• An Acknowledge Condition

18.4.17 MULTI -MASTER COMMUNICATION,

BUS COLLISION AND BUS

ARBITRATION

Multi-Master mode support is achieved by bus arbitra-

tion. When the master outputs address/data bits onto

the SDA pin, arbitration takes place when the master

outputs a ‘1’ on SDA, by letting SDA float high and

another master asserts a ‘0’. When the SCL pin floats

high, data should be stable. If the expected data on

SDA is a ‘1’ and the data sampled on the SDA pin = 0,

then a bus collision has taken place. The master will set

the Bus Collision Interrupt Flag, BCLIF and reset the

I2C port to its Idle state (Figure 18-27).

If a transmit was in progress when the bus collision

occurred, the transmission is halted, the BF flag is

cleared, the SDA and SCL lines are deasserted and the

SSPBUF can be written to. When the user services the

bus collision Interrupt Service Routine and if the I2C

bus is free, the user can resume communication by

asserting a Start condition.

If a Start, Repeated Start, Stop or Acknowledge

condition was in progress when the bus collision

occurred, the condition is aborted, the SDA and SCL

lines are deasserted and the respective control bits in

the SSPCON2 register are cleared. When the user ser-

vices the bus collision Interrupt Service Routine and if

the I2C bus is free, the user can resume communication

by asserting a Start condition.

The master will continue to monitor the SDA and SCL

pins. If a Stop condition occurs, the SSPIF bit will be set.

A write to the SSPBUF will start the transmission of

data at the first data bit, regardless of where the

transmitter left off when the bus collision occurred.

In Multi-Master mode, the interrupt generation on the

detection of Start and Stop conditions allows the

determination of when the bus is free. Control of the I2C

bus can be taken when the P bit is set in the SSPSTAT

cleared.

FIGURE 18-27: BUS COLLISION TIMING FOR TRANSMIT AND ACKNOWLEDGE

SDA

SCL

BCLIF

SDA released

SDA line pulled low

by another source

Sample SDA. While SCL is high,

data doesn’t match what is driven

Bus collision has occurred.

Set bus collision

interrupt (BCLIF)

by the master.

by master

Data changes

while SCL = 0

PIC18F2221/2321/4221/4321 FAMILY

18.4.17.1 Bus Collision During a

Start Condition

During a Start condition, a bus collision occurs if:

a) SDA or SCL are sampled low at the beginning of

the Start condition (Figure 18-28).

b) SCL is sampled low before SDA is asserted low

(Figure 18-29).

During a Start condition, both the SDA and the SCL

pins are monitored.

If the SDA pin is already low, or the SCL pin is already

low, then all of the following occur:

• the Start condition is aborted,

• the BCLIF flag is set and

• the MSSP module is reset to its Idle state

(Figure 18-28).

The Start condition begins with the SDA and SCL pins

deasserted. When the SDA pin is sampled high, the

Baud Rate Generator is loaded from SSPADD<6:0>

and counts down to 0. If the SCL pin is sampled low

while SDA is high, a bus collision occurs because it is

assumed that another master is attempting to drive a

data ‘1’ during the Start condition.

If the SDA pin is sampled low during this count, the

BRG is reset and the SDA line is asserted early

(Figure 18-30). If, however, a ‘1’ is sampled on the SDA

pin, the SDA pin is asserted low at the end of the BRG

count. The Baud Rate Generator is then reloaded and

counts down to 0; if the SCL pin is sampled as ‘0’

during this time, a bus collision does not occur. At the

end of the BRG count, the SCL pin is asserted low.

FIGURE 18-28: BUS COLLISION DURING START CONDITION (SDA ONLY)

Note: The reason that bus collision is not a factor

during a Start condition is that no two bus

masters can assert a Start condition at the

exact same time. Therefore, one master

will always assert SDA before the other.

This condition does not cause a bus

collision because the two masters must be

allowed to arbitrate the first address

following the Start condition. If the address

is the same, arbitration must be allowed to

continue into the data portion, Repeated

Start or Stop conditions.

SDA

SCL

SEN

SDA sampled low before

SDA goes low before the SEN bit is set.

S bit and SSPIF set because

MSSP module reset into Idle state.

SEN cleared automatically because of bus collision.

S bit and SSPIF set because

Set SEN, enable Start

condition if SDA = 1, SCL = 1

SDA = 0, SCL = 1.

BCLIF

SSPIF

SDA = 0, SCL = 1.

SSPIF and BCLIF are

cleared in software

SSPIF and BCLIF are

cleared in software

Set BCLIF,

Start condition. Set BCLIF.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 18-29: BUS COLLISION DURING START CONDITION (SCL = 0)

FIGURE 18-30: BRG RESET DUE TO SDA ARBITRATION DURING START CONDITION

SDA

SCL

SEN bus collision occurs. Set BCLIF.

SCL = 0 before SDA = 0,

Set SEN, enable Start

sequence if SDA = 1, SCL = 1

TBRG TBRG

SDA = 0, SCL = 1

BCLIF

SSPIF

Interrupt cleared

in software

bus collision occurs. Set BCLIF.

SCL = 0 before BRG time-out,

‘0’‘0’

SDA

SCL

SEN

Set S

Less than TBRG TBRG

SDA = 0, SCL = 1

BCLIF

SSPIF

Interrupts cleared

in software

set SSPIF

SDA = 0, SCL = 1,

SCL pulled low after BRG

time-out

Set SSPIF

‘0’

SDA pulled low by other master.

Reset BRG and assert SDA.

Set SEN, enable Start

sequence if SDA = 1, SCL = 1

PIC18F2221/2321/4221/4321 FAMILY

18.4.17.2 Bus Collision During a Repeated

Start Condition

During a Repeated Start condition, a bus collision

occurs if:

a) A low level is sampled on SDA when SCL goes

from low level to high level.

b) SCL goes low before SDA is asserted low,

indicating that another master is attempting to

transmit a data ‘1’.

When the user deasserts SDA and the pin is allowed to

float high, the BRG is loaded with SSPADD<6:0> and

counts down to 0. The SCL pin is then deasserted and

when sampled high, the SDA pin is sampled.

If SDA is low, a bus collision has occurred (i.e., another

master is attempting to transmit a data ‘0’, Figure 18-31).

If SDA is sampled high, the BRG is reloaded and begins

counting. If SDA goes from high-to-low before the BRG

times out, no bus collision occurs because no two

masters can assert SDA at exactly the same time.

If SCL goes from high-to-low before the BRG times out

and SDA has not already been asserted, a bus collision

occurs. In this case, another master is attempting to

transmit a data ‘1’ during the Repeated Start condition,

see Figure 18-32.

If, at the end of the BRG time-out, both SCL and SDA

are still high, the SDA pin is driven low and the BRG is

reloaded and begins counting. At the end of the count,

regardless of the status of the SCL pin, the SCL pin is

driven low and the Repeated Start condition is

complete.

FIGURE 18-31: BUS COLLISION DURING A REPEATED START CONDITION (CASE 1)

FIGURE 18-32: BUS COLLISION DURING REPEATED START CONDITION (CASE 2)

SDA

SCL

RSEN

BCLIF

SSPIF

Sample SDA when SCL goes high.

If SDA = 0, set BCLIF and release SDA and SCL.

Cleared in software

‘0’

SDA

SCL

BCLIF

RSEN

SSPIF

Interrupt cleared

in software

SCL goes low before SDA,

set BCLIF. Release SDA and SCL.

TBRG TBRG

‘0’

PIC18F2221/2321/4221/4321 FAMILY

18.4.17.3 Bus Collision During a Stop

Condition

Bus collision occurs during a Stop condition if:

a) After the SDA pin has been deasserted and

allowed to float high, SDA is sampled low after

the BRG has timed out.

b) After the SCL pin is deasserted, SCL is sampled

low before SDA goes high.

The Stop condition begins with SDA asserted low.

When SDA is sampled low, the SCL pin is allowed to

float. When the pin is sampled high (clock arbitration),

the Baud Rate Generator is loaded with SSPADD<6:0>

and counts down to 0. After the BRG times out, SDA is

sampled. If SDA is sampled low, a bus collision has

occurred. This is due to another master attempting to

drive a data ‘0’ (Figure 18-33). If the SCL pin is

sampled low before SDA is allowed to float high, a bus

collision occurs. This is another case of another master

attempting to drive a data ‘0’ (Figure 18-34).

FIGURE 18-33: BUS COLLISION DURING A STOP CONDITION (CASE 1)

FIGURE 18-34: BUS COLLISION DURING A STOP CONDITION (CASE 2)

SDA

SCL

BCLIF

PEN

SSPIF

TBRG TBRG TBRG

SDA asserted low

SDA sampled

low after TBRG,

set BCLIF

‘0’

SDA

SCL

BCLIF

PEN

SSPIF

TBRG TBRG TBRG

Assert SDA SCL goes low before SDA goes high,

set BCLIF

‘0’

PIC18F2221/2321/4221/4321 FAMILY

TABLE 18-4: REGISTERS ASSOCIATED WITH I2C™ OPERATION

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR1 PSPIF ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

PIR2 OSCFIF CMIF —EEIF BCLIF HLVDIF TMR3IF CCP2IF 58

PIE2 OSCFIE CMIE —EEIE BCLIE HLVDIE TMR3IE CCP2IE 58

IPR2 OSCFIP CMIP —EEIP BCLIP HLVDIP TMR3IP CCP2IP 58

TRISC TRISC7 TRISC6 TRISC5 TRISC4 TRISC3 TRISC2 TRISC1 TRISC0 58

TRISD TRISD7 TRISD6 TRISD5 TRISD4 TRISD3 TRISD2 TRISD1 TRISD0 58

SSPBUF MSSP Receive Buffer/Transmit Register 56

SSPADD ADD7 ADD6 ADD5 ADD4 ADD3 ADD2 ADD1 ADD0 56

TMR2 Timer2 Register 56

PR2 Timer2 Period Register 56

SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 56

SSPCON2 GCEN ACKSTAT ACKDT/

ADMSK5

ACKEN/

ADMSK5

RCEN/

ADMSK5

PEN/

ADMSK5

RSEN/

ADMSK5

SEN 56

SSPSTAT SMP CKE D/A PSR/WUA BF 56

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the MSSP module in I2C mode.

PIC18F2221/2321/4221/4321 FAMILY

19.0 ENHANCED UNIVERSAL

SYNCHRONOUS

ASYNCHRONOUS RECEIVER

TRANSMITTER (EUSART)

The Enhanced Universal Synchronous Asynchronous

Receiver Transmitter (EUSART) module is one of the

two serial I/O modules. (Generically, the USART is also

known as a Serial Communications Interface or SCI.)

The EUSART can be configured as a full-duplex

asynchronous system that can communicate with

peripheral devices, such as CRT terminals and

personal computers. It can also be configured as a half-

duplex synchronous system that can communicate

with peripheral devices, such as A/D or D/A integrated

circuits, serial EEPROMs, etc.

The Enhanced USART module implements additional

features, including automatic baud rate detection and

calibration, automatic wake-up on Sync Break recep-

tion and 12-bit Break character transmit. These make it

ideally suited for use in Local Interconnect Network bus

(LIN/J2602 bus) systems.

The EUSART can be configured in the following

modes:

• Asynchronous (full duplex) with:

- Auto-wake-up on Break signal

- Auto-baud calibration

- 12-bit Break character transmission

• Synchronous – Master (half duplex) with

selectable clock polarity

• Synchronous – Slave (half duplex) with selectable

clock polarity

The pins of the Enhanced USART are multiplexed

with PORTC. In order to configure RC6/TX/CK and

RC7/RX/DT as an EUSART:

• bit SPEN (RCSTA<7>) must be set (= 1)

• bit TRISC<7> must be set (= 1)

• bit TRISC<6> must be set (= 1)

The operation of the Enhanced USART module is

controlled through three registers:

• Transmit Status and Control (TXSTA)

• Receive Status and Control (RCSTA)

• Baud Rate Control (BAUDCON)

These are detailed on the following pages in

respectively.

Note: The EUSART control will automatically

reconfigure the pin from input to output as

needed.

PIC18F2221/2321/4221/4321 FAMILY

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R-1 R/W-0

CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D

bit 7 bit 0

bit 7 CSRC: Clock Source Select bit

Asynchronous mode:

Don’t care.

Synchronous mode:

1 = Master mode (clock generated internally from BRG)

0 = Slave mode (clock from external source)

bit 6 TX9: 9-bit Transmit Enable bit

1 = Selects 9-bit transmission

0 = Selects 8-bit transmission

bit 5 TXEN: Transmit Enable bit

1 = Transmit enabled

0 = Transmit disabled

Note: SREN/CREN overrides TXEN in Sync mode.

bit 4 SYNC: EUSART Mode Select bit

1 = Synchronous mode

0 = Asynchronous mode

bit 3 SENDB: Send Break Character bit

Asynchronous mode:

1 = Send Sync Break on next transmission (cleared by hardware upon completion)

0 = Sync Break transmission completed

Synchronous mode:

Don’t care.

bit 2 BRGH: High Baud Rate Select bit

Asynchronous mode:

1 = High speed

0 = Low speed

Synchronous mode:

Unused in this mode.

bit 1 TRMT: Transmit Shift Register Status bit

1 = TSR empty

0 = TSR full

bit 0 TX9D: 9th bit of Transmit Data

Can be address/data bit or a parity bit.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R-0 R-0 R-x

SPEN RX9 SREN CREN ADDEN FERR OERR RX9D

bit 7 bit 0

bit 7 SPEN: Serial Port Enable bit

1 = Serial port enabled (configures RX/DT and TX/CK pins as serial port pins)

0 = Serial port disabled (held in Reset)

bit 6 RX9: 9-bit Receive Enable bit

1 = Selects 9-bit reception

0 = Selects 8-bit reception

bit 5 SREN: Single Receive Enable bit

Asynchronous mode:

Don’t care.

Synchronous mode – Master:

1 = Enables single receive

0 = Disables single receive

This bit is cleared after reception is complete.

Synchronous mode – Slave:

Don’t care.

bit 4 CREN: Continuous Receive Enable bit

Asynchronous mode:

1 = Enables receiver

0 = Disables receiver

Synchronous mode:

1 = Enables continuous receive until enable bit CREN is cleared (CREN overrides SREN)

0 = Disables continuous receive

bit 3 ADDEN: Address Detect Enable bit

Asynchronous mode 9-bit (RX9 = 1):

1 = Enables address detection, enables interrupt and loads the receive buffer when RSR<8>

is set

0 = Disables address detection, all bytes are received and ninth bit can be used as parity bit

Asynchronous mode 9-bit (RX9 = 0):

Don’t care.

bit 2 FERR: Framing Error bit

1 = Framing error (can be updated by reading RCREG register and receiving next valid byte)

0 = No framing error

bit 1 OERR: Overrun Error bit

1 = Overrun error (can be cleared by clearing bit CREN)

0 = No overrun error

bit 0 RX9D: 9th bit of Received Data

This can be address/data bit or a parity bit and must be calculated by user firmware.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

R/W-0 R-1 R/W-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0

ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN

bit 7 bit 0

bit 7 ABDOVF: Auto-Baud Acquisition Rollover Status bit

1 = A BRG rollover has occurred during Auto-Baud Rate Detect mode

(must be cleared in software)

0 = No BRG rollover has occurred

bit 6 RCIDL: Receive Operation Idle Status bit

1 = Receive operation is Idle

0 = Receive operation is active

bit 5 RXDTP: Received Data Polarity Select bit

Asynchronous mode:

1 = Receive data (RX) is inverted (active-low)

0 = Receive data (RX) is not inverted (active-high)

Synchronous mode:

No affect.

bit 4 TXCKP: Clock and Data Polarity Select bit

Asynchronous mode:

1 = Idle state for transmit (TX) is a low level

0 = Idle state for transmit (TX) is a high level

Synchronous mode:

1 = Idle state for clock (CK) is a high level

0 = Idle state for clock (CK) is a low level

bit 3 BRG16: 16-bit Baud Rate Register Enable bit

1 = 16-bit Baud Rate Generator – SPBRGH and SPBRG

0 = 8-bit Baud Rate Generator – SPBRG only (Compatible mode), SPBRGH value ignored

bit 2 Unimplemented: Read as ‘0’

bit 1 WUE: Wake-up Enable bit

Asynchronous mode:

1 = EUSART will continue to sample the RX pin – interrupt generated on falling edge; bit

cleared in hardware on following rising edge

0 = RX pin not monitored or rising edge detected

Synchronous mode:

Unused in this mode.

bit 0 ABDEN: Auto-Baud Detect Enable bit

Asynchronous mode:

1 = Enable baud rate measurement on the next character. Requires reception of a Sync field

(55h); cleared in hardware upon completion

0 = Baud rate measurement disabled or completed

Synchronous mode:

Unused in this mode.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

19.1 Baud Rate Generator (BRG)

The BRG is a dedicated 8-bit or 16-bit generator that

supports both the Asynchronous and Synchronous

modes of the EUSART. By default, the BRG operates

in 8-bit mode; setting the BRG16 bit (BAUDCON<3>)

selects 16-bit mode.

The SPBRGH:SPBRG register pair controls the period

of a free running timer. In Asynchronous mode, bits

BRGH (TXSTA<2>) and BRG16 (BAUDCON<3>) also

control the baud rate. In Synchronous mode, BRGH is

ignored. Table 19-1 shows the formula for computation

of the baud rate for different EUSART modes which

only apply in Master mode (internally generated clock).

Given the desired baud rate and FOSC, the nearest

integer value for the SPBRGH:SPBRG registers can be

calculated using the formulas in Table 19-1. From this,

the error in baud rate can be determined. An example

calculation is shown in Example 19-1. Typical baud

rates and error values for the various Asynchronous

modes are shown in Table 19-2. It may be advantageous

to use the high baud rate (BRGH = 1) or the 16-bit BRG

to reduce the baud rate error, or achieve a slow baud

rate for a fast oscillator frequency.

Writing a new value to the SPBRGH:SPBRG registers

causes the BRG timer to be reset (or cleared). This

ensures the BRG does not wait for a timer overflow

before outputting the new baud rate.

19.1.1 OPERATION IN POWER-MANAGED

MODES

The device clock is used to generate the desired baud

rate. When one of the power-managed modes is

entered, the new clock source may be operating at a

different frequency. This may require an adjustment to

the value in the SPBRG register pair.

19.1.2 SAMPLING

The data on the RX pin is sampled three times by a

majority detect circuit to determine if a high or a low

level is present at the RX pin when SYNC is clear or

when BRG16 and BRGH are both not set. The data on

the RX pin is sampled once when SYNC is set or when

BRGH16 and BRGH are both set.

TABLE 19-1: BAUD RATE FORMULAS

Note: A BRG value of 0 is not supported.

Configuration Bits BRG/EUSART Mode Baud Rate Formula

SYNC BRG16 BRGH

000 8-bit/Asynchronous FOSC/[64 (n + 1)]

001 8-bit/Asynchronous FOSC/[16 (n + 1)]

010 16-bit/Asynchronous

011 16-bit/Asynchronous

FOSC/[4 (n + 1)]10x 8-bit/Synchronous

11x 16-bit/Synchronous

Legend: x = Don’t care, n = value of SPBRGH:SPBRG register pair

PIC18F2221/2321/4221/4321 FAMILY

EXAMPLE 19-1: CALCULATING BAUD RATE ERROR

TABLE 19-2: REGISTERS ASSOCIATED WITH BAUD RATE GENERATOR

For a device with FOSC of 16 MHz, desired baud rate of 9600, Asynchronous mode, 8-bit BRG:

Desired Baud Rate = FOSC/(64 ([SPBRGH:SPBRG] + 1))

Solving for SPBRGH:SPBRG:

X=((FOSC/Desired Baud Rate)/64) – 1

= ((16000000/9600)/64) – 1

= [25.042] = 25

Calculated Baud Rate = 16000000/(64 (25 + 1))

= 9615

Error = (Calculated Baud Rate – Desired Baud Rate)/Desired Baud Rate

= (9615 – 9600)/9600 = 0.16%

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values

on page

TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57

RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57

BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 —WUE ABDEN 57

SPBRGH EUSART Baud Rate Generator Register High Byte 57

SPBRG EUSART Baud Rate Generator Register Low Byte 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the BRG.

PIC18F2221/2321/4221/4321 FAMILY

TABLE 19-3: BAUD RATES FOR ASYNCHRONOUS MODES

BAUD

RATE

(K)

SYNC = 0, BRGH = 0, BRG16 = 0

FOSC = 40.000 MHz FOSC = 20.000 MHz FOSC = 10.000 MHz FOSC = 8.000 MHz

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

0.3————————————

1.2 — — — 1.221 1.73 255 1.202 0.16 129 1.201 -0.16 103

2.4 2.441 1.73 255 2.404 0.16 129 2.404 0.16 64 2.403 -0.16 51

9.6 9.615 0.16 64 9.766 1.73 31 9.766 1.73 15 9.615 -0.16 12

19.2 19.531 1.73 31 19.531 1.73 15 19.531 1.73 7 — — —

57.6 56.818 -1.36 10 62.500 8.51 4 52.083 -9.58 2 — — —

115.2 125.000 8.51 4 104.167 -9.58 2 78.125 -32.18 1 — — —

BAUD

RATE

(K)

SYNC = 0, BRGH = 0, BRG16 = 0

FOSC = 4.000 MHz FOSC = 2.000 MHz FOSC = 1.000 MHz

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

0.3 0.300 0.16 207 0.300 -0.16 103 0.300 -0.16 51

1.2 1.202 0.16 51 1.201 -0.16 25 1.201 -0.16 12

2.4 2.404 0.16 25 2.403 -0.16 12 — — —

9.6 8.929 -6.99 6 — — — — — —

19.2 20.833 8.51 2 — — — — — —

57.6 62.500 8.51 0 — — — — — —

115.2 62.500 -45.75 0 — — — — — —

BAUD

RATE

(K)

SYNC = 0, BRGH = 1, BRG16 = 0

FOSC = 40.000 MHz FOSC = 20.000 MHz FOSC = 10.000 MHz FOSC = 8.000 MHz

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

0.3————————————

1.2————————————

2.4 — — — — — — 2.441 1.73 255 2.403 -0.16 207

9.6 9.766 1.73 255 9.615 0.16 129 9.615 0.16 64 9.615 -0.16 51

19.2 19.231 0.16 129 19.231 0.16 64 19.531 1.73 31 19.230 -0.16 25

57.6 58.140 0.94 42 56.818 -1.36 21 56.818 -1.36 10 55.555 3.55 8

115.2 113.636 -1.36 21 113.636 -1.36 10 125.000 8.51 4 — — —

BAUD

RATE

(K)

SYNC = 0, BRGH = 1, BRG16 = 0

FOSC = 4.000 MHz FOSC = 2.000 MHz FOSC = 1.000 MHz

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

0.3 — — — — — — 0.300 -0.16 207

1.2 1.202 0.16 207 1.201 -0.16 103 1.201 -0.16 51

2.4 2.404 0.16 103 2.403 -0.16 51 2.403 -0.16 25

9.6 9.615 0.16 25 9.615 -0.16 12 — — —

19.2 19.231 0.16 12 — — — — — —

57.6 62.500 8.51 3 — — — — — —

115.2 125.000 8.51 1 — — — — — —

PIC18F2221/2321/4221/4321 FAMILY

BAUD

RATE

(K)

SYNC = 0, BRGH = 0, BRG16 = 1

FOSC = 40.000 MHz FOSC = 20.000 MHz FOSC = 10.000 MHz FOSC = 8.000 MHz

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

0.3 0.300 0.00 8332 0.300 0.02 4165 0.300 0.02 2082 0.300 -0.04 1665

1.2 1.200 0.02 2082 1.200 -0.03 1041 1.200 -0.03 520 1.201 -0.16 415

2.4 2.402 0.06 1040 2.399 -0.03 520 2.404 0.16 259 2.403 -0.16 207

9.6 9.615 0.16 259 9.615 0.16 129 9.615 0.16 64 9.615 -0.16 51

19.2 19.231 0.16 129 19.231 0.16 64 19.531 1.73 31 19.230 -0.16 25

57.6 58.140 0.94 42 56.818 -1.36 21 56.818 -1.36 10 55.555 3.55 8

115.2 113.636 -1.36 21 113.636 -1.36 10 125.000 8.51 4 — — —

BAUD

RATE

(K)

SYNC = 0, BRGH = 0, BRG16 = 1

FOSC = 4.000 MHz FOSC = 2.000 MHz FOSC = 1.000 MHz

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

0.3 0.300 0.04 832 0.300 -0.16 415 0.300 -0.16 207

1.2 1.202 0.16 207 1.201 -0.16 103 1.201 -0.16 51

2.4 2.404 0.16 103 2.403 -0.16 51 2.403 -0.16 25

9.6 9.615 0.16 25 9.615 -0.16 12 — — —

19.2 19.231 0.16 12 — — — — — —

57.6 62.500 8.51 3 — — — — — —

115.2 125.000 8.51 1 — — — — — —

BAUD

RATE

(K)

SYNC = 0, BRGH = 1, BRG16 = 1 or SYNC = 1, BRG16 = 1

FOSC = 40.000 MHz FOSC = 20.000 MHz FOSC = 10.000 MHz FOSC = 8.000 MHz

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

0.3 0.300 0.00 33332 0.300 0.00 16665 0.300 0.00 8332 0.300 -0.01 6665

1.2 1.200 0.00 8332 1.200 0.02 4165 1.200 0.02 2082 1.200 -0.04 1665

2.4 2.400 0.02 4165 2.400 0.02 2082 2.402 0.06 1040 2.400 -0.04 832

9.6 9.606 0.06 1040 9.596 -0.03 520 9.615 0.16 259 9.615 -0.16 207

19.2 19.193 -0.03 520 19.231 0.16 259 19.231 0.16 129 19.230 -0.16 103

57.6 57.803 0.35 172 57.471 -0.22 86 58.140 0.94 42 57.142 0.79 34

115.2 114.943 -0.22 86 116.279 0.94 42 113.636 -1.36 21 117.647 -2.12 16

BAUD

RATE

(K)

SYNC = 0, BRGH = 1, BRG16 = 1 or SYNC = 1, BRG16 = 1

FOSC = 4.000 MHz FOSC = 2.000 MHz FOSC = 1.000 MHz

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

Actual

Rate

(K)

Error

SPBRG

value

(decimal)

0.3 0.300 0.01 3332 0.300 -0.04 1665 0.300 -0.04 832

1.2 1.200 0.04 832 1.201 -0.16 415 1.201 -0.16 207

2.4 2.404 0.16 415 2.403 -0.16 207 2.403 -0.16 103

9.6 9.615 0.16 103 9.615 -0.16 51 9.615 -0.16 25

19.2 19.231 0.16 51 19.230 -0.16 25 19.230 -0.16 12

57.6 58.824 2.12 16 55.555 3.55 8 — — —

115.2 111.111 -3.55 8 — — — — — —

TABLE 19-3: BAUD RATES FOR ASYNCHRONOUS MODES (CONTINUED)

PIC18F2221/2321/4221/4321 FAMILY

19.1.3 AUTO-BAUD RATE DETECT

The Enhanced USART module supports the automatic

detection and calibration of baud rate. This feature is

active only in Asynchronous mode and while the WUE

bit is clear.

The automatic baud rate measurement sequence

(Figure 19-1) begins whenever a Start bit is received

and the ABDEN bit is set. The calculation is

self-averaging.

In the Auto-Baud Rate Detect (ABD) mode, the clock to

the BRG is reversed. Rather than the BRG clocking the

incoming RX signal, the RX signal is timing the BRG. In

ABD mode, the internal Baud Rate Generator is used

as a counter to time the bit period of the incoming serial

byte stream.

Once the ABDEN bit is set, the state machine will clear

the BRG and look for a Start bit. The Auto-Baud Rate

Detect must receive a byte with the value 55h (ASCII

“U”, which is also the LIN/J2602 bus Sync character) in

order to calculate the proper bit rate. The measurement

is taken over both a low and a high bit time in order to

minimize any effects caused by asymmetry of the incom-

ing signal. After a Start bit, the SPBRG begins counting

up, using the preselected clock source on the first rising

edge of RX. After eight bits on the RX pin, or the fifth ris-

ing edge, an accumulated value totalling the proper BRG

period is left in the SPBRGH:SPBRG register pair. Once

the 5th edge is seen (this should correspond to the Stop

bit), the ABDEN bit is automatically cleared.

If a rollover of the BRG occurs (an overflow from FFFFh

to 0000h), the event is trapped by the ABDOVF status

bit (BAUDCON<7>). It is set in hardware by BRG

rollovers and can be set or cleared by the user in

software. ABD mode remains active after rollover

events and the ABDEN bit remains set (Figure 19-2).

While calibrating the baud rate period, the BRG

registers are clocked at 1/8th the preconfigured clock

rate. Note that the BRG clock can be configured by the

BRG16 and BRGH bits. The BRG16 bit must be set to

use both SPBRG1 and SPBRGH1 as a 16-bit counter

This allows the user to verify that no carry occurred for

8-bit modes by checking for 00h in the SPBRGH

the BRG.

While the ABD sequence takes place, the EUSART

state machine is held in Idle. The RCIF interrupt is set

once the fifth rising edge on RX is detected. The value

in the RCREG needs to be read to clear the RCIF

interrupt. The contents of RCREG should be discarded.

TABLE 19-4: BRG COUNTER

CLOCK RATES

19.1.3.1 ABD and EUSART Transmission

Since the BRG clock is reversed during ABD acquisi-

tion, the EUSART transmitter cannot be used during

ABD. This means that whenever the ABDEN bit is set,

TXREG cannot be written to. Users should also ensure

that ABDEN does not become set during a transmit

sequence. Failing to do this may result in unpredictable

EUSART operation.

Note 1: If the WUE bit is set with the ABDEN bit,

Auto-Baud Rate Detection will occur on

the byte following the Break character.

2: It is up to the user to determine that the

incoming character baud rate is within the

range of the selected BRG clock source.

Some combinations of oscillator frequency

and EUSART baud rates are not possible

due to bit error rates. Overall system

timing and communication baud rates

must be taken into consideration when

using the Auto-Baud Rate Detection

feature.

3: To maximize the baud rate range, it is

recommended to set the BRG16 bit if the

auto-baud feature is used.

BRG16 BRGH BRG Counter Clock

00 FOSC/512

01 FOSC/128

10 FOSC/128

11 FOSC/32

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 19-1: AUTOMATIC BAUD RATE CALCULATION

FIGURE 19-2: BRG OVERFLOW SEQUENCE

BRG Value

RX pin

ABDEN bit

RCIF bit

Bit 0 Bit 1

(Interrupt)

Read

RCREG

BRG Clock

Start

Auto-Cleared

Set by User

XXXXh 0000h

Edge #1

Bit 2 Bit 3

Edge #2

Bit 4 Bit 5

Edge #3

Bit 6 Bit 7

Edge #4

Stop Bit

Edge #5

001Ch

Note: The ABD sequence requires the EUSART module to be configured in Asynchronous mode and WUE = 0.

SPBRG XXXXh 1Ch

SPBRGH XXXXh 00h

Start Bit 0

XXXXh 0000h 0000h

FFFFh

BRG Clock

ABDEN bit

RX pin

ABDOVF bit

BRG Value

PIC18F2221/2321/4221/4321 FAMILY

19.2 EUSART Asynchronous Mode

The Asynchronous mode of operation is selected by

clearing the SYNC bit (TXSTA<4>). In this mode, the

EUSART uses standard Non-Return-to-Zero (NRZ)

format (one Start bit, eight or nine data bits and one

Stop bit). The most common data format is 8 bits. An

on-chip dedicated 8-bit/16-bit Baud Rate Generator

can be used to derive standard baud rate frequencies

from the oscillator.

The EUSART transmits and receives the LSb first. The

EUSART’s transmitter and receiver are functionally

independent but use the same data format and baud

rate. The Baud Rate Generator produces a clock, either

x16 or x64 of the bit shift rate depending on the BRGH

and BRG16 bits (TXSTA<2> and BAUDCON<3>). Parity

is not supported by the hardware but can be

implemented in software and stored as the 9th data bit.

The TXCKP (BAUDCON<4>) and RXDTP

(BAUDCON<5>) bits allow the TX and RX signals to be

inverted (polarity reversed). Devices that buffer signals

between TTL and RS-232 levels also invert the signal.

Setting the TXCKP and RXDTP bits allows for the use of

circuits that provide buffering without inverting the signal.

In Asynchronous mode, clock polarity is selected with

the TXCKP bit (BAUDCON<4>). Setting TXCKP sets

the Idle state on CK as high, while clearing the bit sets

the Idle state as low. Data polarity is selected with the

RXDTP bit (BAUDCON<5>). Setting RXDTP inverts

data on RX, while clearing the bit has no affect on

received data.

When operating in Asynchronous mode, the EUSART

module consists of the following important elements:

• Baud Rate Generator

• Sampling Circuit

• Asynchronous Transmitter

• Asynchronous Receiver

• Auto-Wake-up on Break signal

• 12-bit Break Character Transmit

• Auto-Baud Rate Detection

• Pin State Polarity

19.2.1 EUSART ASYNCHRONOUS

TRANSMITTER

The EUSART transmitter block diagram is shown in

Figure 19-3. The heart of the transmitter is the Transmit

(Serial) Shift Register (TSR). The Shift register obtains

its data from the Read/Write Transmit Buffer register,

TXREG. The TXREG register is loaded with data in

software. The TSR register is not loaded until the Stop

bit has been transmitted from the previous load. As

soon as the Stop bit is transmitted, the TSR is loaded

with new data from the TXREG register (if available).

Once the TXREG register transfers the data to the TSR

CY), the TXREG register is empty

and the TXIF flag bit (PIR1<4>) is set. This interrupt can

be enabled or disabled by setting or clearing the interrupt

enable bit, TXIE (PIE1<4>). TXIF will be set regardless of

the state of TXIE; it cannot be cleared in software. TXIF

is also not cleared immediately upon loading TXREG, but

becomes valid in the second instruction cycle following

the load instruction. Polling TXIF immediately following a

load of TXREG will return invalid results.

While TXIF indicates the status of the TXREG register,

another bit, TRMT (TXSTA<1>), shows the status of

the TSR register. TRMT is a read-only bit which is set

when the TSR register is empty. No interrupt logic is

tied to this bit so the user has to poll this bit in order to

determine if the TSR register is empty.

The TXCKP bit (BAUDCON<4>) allows the TX signal to

be inverted (polarity reversed). Devices that buffer

signals from TTL to RS-232 levels also invert the signal

(when TTL = 1, RS-232 = negative). Inverting the

polarity of the TX pin data by setting the TXCKP bit

allows for use of circuits that provide buffering without

inverting the signal.

To set up an Asynchronous Transmission:

1. Initialize the SPBRGH:SPBRG registers for the

appropriate baud rate. Set or clear the BRGH

and BRG16 bits, as required, to achieve the

desired baud rate.

2. Enable the asynchronous serial port by clearing

bit, SYNC, and setting bit, SPEN.

3. If the signal from the TX pin is to be inverted, set

the TXCKP bit.

4. If interrupts are desired, set enable bit, TXIE.

5. If 9-bit transmission is desired, set transmit bit,

TX9; can be used as address/data bit.

6. Enable the transmission by setting bit, TXEN,

which will also set bit, TXIF.

7. If 9-bit transmission is selected, the ninth bit

should be loaded in bit, TX9D.

8. Load data to the TXREG register (starts

transmission).

9. If using interrupts, ensure that the GIE and PEIE

bits in the INTCON register (INTCON<7:6>) are

set.

Note 1: The TSR register is not mapped in data

memory so it is not available to the user.

2: Flag bit TXIF is set when enable bit TXEN

is set.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 19-3: EUSART TRANSMIT BLOCK DIAGRAM

FIGURE 19-4: ASYNCHRONOUS TRANSMISSION, TXCKP = 0 (TX NOT INVERTED)

FIGURE 19-5: ASYNCHRONOUS TRANSMISSION (BACK TO BACK),

TXCKP = 0 (TX NOT INVERTED)

TXIF

TXIE

Interrupt

TXEN Baud Rate CLK

SPBRG

Baud Rate Generator TX9D

MSb LSb

Data Bus

TXREG Register

TSR Register

(8) 0

TX9

TRMT SPEN

TX pin

Pin Buffer

and Control

• • •

SPBRGH

BRG16

TXCKP

Word 1

Transmit Shift Reg

Start bit bit 0 bit 1 bit 7/8

Write to TXREG

BRG Output

(Shift Clock)

TX (pin)

TXIF bit

(Transmit Buffer

Reg. Empty Flag)

TRMT bit

(Transmit Shift

Reg. Empty Flag)

1 TCY

Stop bit

Word 1

Transmit Shift Reg.

Write to TXREG

BRG Output

(Shift Clock)

TX (pin)

TXIF bit

(Interrupt Reg. Flag)

TRMT bit

(Transmit Shift

Reg. Empty Flag)

Word 1 Word 2

Stop bit Start bit

Transmit Shift Reg.

Word 1 Word 2

bit 0 bit 1 bit 7/8 bit 0

Note: This timing diagram shows two consecutive transmissions.

1 TCY

Start bit

PIC18F2221/2321/4221/4321 FAMILY

TABLE 19-5: REGISTERS ASSOCIATED WITH ASYNCHRONOUS TRANSMISSION

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57

TXREG EUSART Transmit Register 57

TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57

BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 —WUE ABDEN 57

SPBRGH EUSART Baud Rate Generator Register High Byte 57

SPBRG EUSART Baud Rate Generator Register Low Byte 57

Legend: — = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous transmission.

Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

19.2.2 EUSART ASYNCHRONOUS

RECEIVER

The receiver block diagram is shown in Figure 19-6.

The data is received on the RX pin and drives the data

recovery block. The data recovery block is actually a

high-speed shifter operating at x16 times the baud rate,

whereas the main receive serial shifter operates at the

bit rate or at FOSC. This mode would typically be used

in RS-232 systems.

The RXDTP bit (BAUDCON<5>) allows the RX signal to

be inverted (polarity reversed). Devices that buffer

signals from RS-232 to TTL levels also perform an inver-

sion of the signal (when RS-232 = positive, TTL = 0).

Inverting the polarity of the RX pin data by setting the

RXDTP bit allows for the use of circuits that provide

buffering without inverting the signal.

To set up an Asynchronous Reception:

1. Initialize the SPBRGH:SPBRG registers for the

appropriate baud rate. Set or clear the BRGH

and BRG16 bits, as required, to achieve the

desired baud rate.

2. Enable the asynchronous serial port by clearing

bit, SYNC, and setting bit, SPEN.

3. If the signal at the RX pin is to be inverted, set

the RXDTP bit.

4. If interrupts are desired, set enable bit, RCIE.

5. If 9-bit reception is desired, set bit, RX9.

6. Enable the reception by setting bit, CREN.

7. Flag bit, RCIF, will be set when reception is

complete and an interrupt will be generated if

enable bit, RCIE, was set.

8. Read the RCSTA register to get the 9th bit (if

enabled) and determine if any error occurred

during reception.

9. Read the 8-bit received data by reading the

RCREG register.

10. If any error occurred, clear the error by clearing

enable bit, CREN.

11. If using interrupts, ensure that the GIE and PEIE

bits in the INTCON register (INTCON<7:6>) are

set.

19.2.3 SETTING UP 9-BIT MODE WITH

ADDRESS DETECT

This mode would typically be used in RS-485 systems.

To set up an Asynchronous Reception with Address

Detect Enable:

1. Initialize the SPBRGH:SPBRG registers for the

appropriate baud rate. Set or clear the BRGH

and BRG16 bits, as required, to achieve the

desired baud rate.

2. Enable the asynchronous serial port by clearing

the SYNC bit and setting the SPEN bit.

3. If the signal at the RX pin is to be inverted, set

the RXDTP bit. If the signal from the TX pin is to

be inverted, set the TXCKP bit.

4. If interrupts are required, set the RCEN bit and

select the desired priority level with the RCIP bit.

5. Set the RX9 bit to enable 9-bit reception.

6. Set the ADDEN bit to enable address detect.

7. Enable reception by setting the CREN bit.

8. The RCIF bit will be set when reception is

complete. The interrupt will be Acknowledged if

the RCIE and GIE bits are set.

9. Read the RCSTA register to determine if any

error occurred during reception, as well as read

bit 9 of data (if applicable).

10. Read RCREG to determine if the device is being

addressed.

11. If any error occurred, clear the CREN bit.

12. If the device has been addressed, clear the

ADDEN bit to allow all received data into the

receive buffer and interrupt the CPU.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 19-6: EUSART RECEIVE BLOCK DIAGRAM

FIGURE 19-7: ASYNCHRONOUS RECEPTION, TXCKP = 0 (TX NOT INVERTED)

TABLE 19-6: REGISTERS ASSOCIATED WITH ASYNCHRONOUS RECEPTION

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57

RCREG EUSART Receive Register 57

TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57

BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN 57

SPBRGH EUSART Baud Rate Generator Register High Byte 57

SPBRG EUSART Baud Rate Generator Register Low Byte 57

Legend: — = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous reception.

Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.

x64 Baud Rate CLK

Baud Rate Generator

Pin Buffer

and Control

SPEN

Data

Recovery

CREN OERR FERR

RSR Register

MSb LSb

RX9D RCREG Register

FIFO

Interrupt RCIF

RCIE

Data Bus

÷ 64

÷ 16

Stop Start

(8) 7 1 0

RX9

• • •

SPBRGSPBRGH

BRG16

÷ 4

RXDTP

Start

bit bit 7/8

bit 1bit 0 bit 7/8 bit 0

Stop

bit

Start

bit

Start

bitbit 7/8 Stop

bit

RX (pin)

Rcv Buffer Reg

Rcv Shift Reg

Read Rcv

Buffer Reg

RCREG

RCIF

(Interrupt Flag)

OERR bit

CREN

Word 1

RCREG

Word 2

RCREG

Stop

bit

Note: This timing diagram shows three words appearing on the RX input. The RCREG (receive buffer) is read after the third word causing

the OERR (overrun) bit to be set.

PIC18F2221/2321/4221/4321 FAMILY

19.2.4 AUTO-WAKE-UP ON SYNC

BREAK CHARACTER

During Sleep mode, all clocks to the EUSART are

suspended. Because of this, the Baud Rate Generator

is inactive and a proper byte reception cannot be per-

formed. The auto-wake-up feature allows the controller

to wake-up due to activity on the RX/DT line while the

EUSART is operating in Asynchronous mode.

The auto-wake-up feature is enabled by setting the

WUE bit (BAUDCON<1>). Once set, the typical receive

sequence on RX/DT is disabled and the EUSART

remains in an Idle state, monitoring for a wake-up event

independent of the CPU mode. A wake-up event

consists of a high-to-low transition on the RX/DT line.

(This coincides with the start of a Sync Break or a

Wake-up Signal character for the LIN/J2602 protocol.)

Following a wake-up event, the module generates an

RCIF interrupt. The interrupt is generated synchro-

nously to the Q clocks in normal operating modes

(Figure 19-8) and asynchronously, if the device is in

Sleep mode (Figure 19-9). The interrupt condition is

cleared by reading the RCREG register.

The WUE bit is automatically cleared once a low-to-

high transition is observed on the RX line following the

wake-up event. At this point, the EUSART module is in

Idle mode and returns to normal operation. This signals

to the user that the Sync Break event is over.

19.2.4.1 Special Considerations Using

Auto-Wake-up

Since auto-wake-up functions by sensing rising edge

transitions on RX/DT, information with any state changes

before the Stop bit may signal a false end-of-character

and cause data or framing errors. To work properly,

therefore, the initial character in the transmission must

be all ‘0’s. This can be 00h (8 bytes) for standard RS-232

devices or 000h (12 bits) for the LIN/J2602 bus.

Oscillator start-up time must also be considered,

especially in applications using oscillators with longer

start-up intervals (i.e., XT or HS mode). The Sync

Break (or Wake-up Signal) character must be of

sufficient length and be followed by a sufficient interval

to allow enough time for the selected oscillator to start

and provide proper initialization of the EUSART.

19.2.4.2 Special Considerations Using

the WUE Bit

The timing of WUE and RCIF events may cause some

confusion when it comes to determining the validity of

received data. As noted, setting the WUE bit places the

EUSART in an Idle mode. The wake-up event causes a

receive interrupt by setting the RCIF bit. The WUE bit is

cleared after this when a rising edge is seen on RX/DT.

The interrupt condition is then cleared by reading the

RCREG register. Ordinarily, the data in RCREG will be

dummy data and should be discarded.

The fact that the WUE bit has been cleared (or is still

set) and the RCIF flag is set should not be used as an

indicator of the integrity of the data in RCREG. Users

should consider implementing a parallel method in

firmware to verify received data integrity.

To assure that no actual data is lost, check the RCIDL

bit to verify that a receive operation is not in process. If

a receive operation is not occurring, the WUE bit may

then be set just prior to entering the Sleep mode.

FIGURE 19-8: AUTO-WAKE-UP BIT (WUE) TIMINGS DURING NORMAL OPERATION

FIGURE 19-9: AUTO-WAKE-UP BIT (WUE) TIMINGS DURING SLEEP

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

OSC1

WUE bit(1)

RX/DT Line

RCIF

Note 1: The EUSART remains in Idle while the WUE bit is set.

Bit set by user

Cleared due to user read of RCREG

Auto-Cleared

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

OSC1

WUE bit(2)

RX/DT Line

RCIF

Bit set by user

Cleared due to user read of RCREG

Sleep Command Executed

Note 1: If the wake-up event requires long oscillator warm-up time, the auto-clear of the WUE bit can occur before the oscillator is ready. This

sequence should not depend on the presence of Q clocks.

2: The EUSART remains in Idle while the WUE bit is set.

Sleep Ends

Note 1

Auto-Cleared

PIC18F2221/2321/4221/4321 FAMILY

19.2.5 BREAK CHARACTER SEQUENCE

The EUSART module has the capability of sending the

special Break character sequences that are required by

the LIN/J2602 bus standard. The Break character

transmit consists of a Start bit, followed by twelve ‘0’

bits and a Stop bit. The Frame Break character is sent

whenever the SENDB and TXEN bits (TXSTA<3> and

TXSTA<5>) are set while the Transmit Shift register is

loaded with data. Note that the value of data written to

TXREG will be ignored and all ‘0’s will be transmitted.

The SENDB bit is automatically reset by hardware after

the corresponding Stop bit is sent. This allows the user

to preload the transmit FIFO with the next transmit byte

following the Break character (typically, the Sync

character in the LIN/J2602 specification).

Note that the data value written to the TXREG for the

Break character is ignored. The write simply serves the

purpose of initiating the proper sequence.

The TRMT bit indicates when the transmit operation is

active or Idle, just as it does during normal transmis-

sion. See Figure 19-10 for the timing of the Break

character sequence.

19.2.5.1 Break and Sync Transmit Sequence

The following sequence will send a message frame

header made up of a Break, followed by an Auto-Baud

Sync byte. This sequence is typical of a LIN/J2602 bus

master.

1. Configure the EUSART for the desired mode.

2. Set the TXEN and SENDB bits to set up the

Break character.

3. Load the TXREG with a dummy character to

initiate transmission (the value is ignored).

4. Write ‘55h’ to TXREG to load the Sync character

into the transmit FIFO buffer.

5. After the Break has been sent, the SENDB bit is

reset by hardware. The Sync character now

transmits in the preconfigured mode.

When the TXREG becomes empty, as indicated by the

TXIF, the next data byte can be written to TXREG.

19.2.6 RECEIVING A BREAK CHARACTER

The Enhanced USART module can receive a Break

character in two ways.

The first method forces configuration of the baud rate

at a frequency of 9/13 the typical speed. This allows for

the Stop bit transition to be at the correct sampling loca-

tion (13 bits for Break versus Start bit and 8 data bits for

typical data).

The second method uses the auto-wake-up feature

described in Section 19.2.4 “Auto-Wake-up on Sync

Break Character”. By enabling this feature, the

EUSART will sample the next two transitions on RX/DT,

cause an RCIF interrupt and receive the next data byte

followed by another interrupt.

Note that following a Break character, the user will

typically want to enable the Auto-Baud Rate Detect

feature. For both methods, the user can set the ABD bit

once the TXIF interrupt is observed.

FIGURE 19-10: SEND BREAK CHARACTER SEQUENCE

Write to TXREG

BRG Output

(Shift Clock)

Start Bit Bit 0 Bit 1 Bit 11 Stop Bit

Break

TXIF bit

(Transmit Buffer

Reg. Empty Flag)

TX (pin)

TRMT bit

(Transmit Shift

Reg. Empty Flag)

SENDB

(Transmit Shift

Reg. Empty Flag)

SENDB sampled here Auto-Cleared

Dummy Write

PIC18F2221/2321/4221/4321 FAMILY

19.3 EUSART Synchronous

Master Mode

The Master mode indicates that the processor trans-

mits the master clock on the CK line. The Synchronous

Master mode is entered by setting the CSRC bit

(TXSTA<7>). In this mode, the data is transmitted in a

half-duplex manner (i.e., transmission and reception do

not occur at the same time). When transmitting data,

the reception is inhibited and vice versa. Synchronous

mode is entered by setting bit SYNC (TXSTA<4>). In

addition, enable bit SPEN (RCSTA<7>) is set in order

to configure the TX and RX pins to CK (clock) and DT

(data) lines, respectively.

The Master mode indicates that the processor

transmits the master clock on the CK line.

Clock polarity (CK) is selected with the TXCKP bit

(BAUDCON<4>). Setting TXCKP sets the Idle state on

CK as high, while clearing the bit sets the Idle state as

low.

19.3.1 EUSART SYNCHRONOUS MASTER

TRANSMISSION

The EUSART transmitter block diagram is shown in

Figure 19-3. The heart of the transmitter is the Transmit

(Serial) Shift Register (TSR). The Shift register obtains

its data from the Read/Write Transmit Buffer register,

TXREG. The TXREG register is loaded with data in

software. The TSR register is not loaded until the last

bit has been transmitted from the previous load. As

soon as the last bit is transmitted, the TSR is loaded

with new data from the TXREG (if available).

Once the TXREG register transfers the data to the TSR

the TXIF flag bit (PIR1<4>) is set. The interrupt can be

enabled or disabled by setting or clearing the interrupt

enable bit, TXIE (PIE1<4>). TXIF is set regardless of

the state of enable bit TXIE; it cannot be cleared in

software. It will reset only when new data is loaded into

the TXREG register.

While flag bit TXIF indicates the status of the TXREG

status of the TSR register. TRMT is a read-only bit which

is set when the TSR is empty. No interrupt logic is tied to

this bit so the user has to poll this bit in order to deter-

mine if the TSR register is empty. The TSR is not

mapped in data memory so it is not available to the user.

To set up a Synchronous Master Transmission:

1. Initialize the SPBRGH:SPBRG registers for the

appropriate baud rate. Set or clear the BRG16

bit, as required, to achieve the desired baud rate.

2. Enable the synchronous master serial port by

setting bits, SYNC, SPEN and CSRC.

3. If the signal from the CK pin is to be inverted, set

the TXCKP bit.

4. If interrupts are desired, set enable bit, TXIE.

5. If 9-bit transmission is desired, set bit, TX9.

6. Enable the transmission by setting bit, TXEN.

7. If 9-bit transmission is selected, the ninth bit

should be loaded in bit, TX9D.

8. Start transmission by loading data to the TXREG

9. If using interrupts, ensure that the GIE and PEIE

bits in the INTCON register (INTCON<7:6>) are

set.

FIGURE 19-11: SYNCHRONOUS TRANSMISSION

bit 0 bit 1 bit 7

Word 1

Q1 Q2 Q3Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

bit 2 bit 0 bit 1 bit 7RC7/RX/DT

RC6/TX/CK pin

Write to

TXREG Reg

TXIF bit

(Interrupt Flag)

TXEN bit ‘1’ ‘1’

Word 2

TRMT bit

Write Word 1 Write Word 2

Note: Sync Master mode, SPBRG = 0, continuous transmission of two 8-bit words.

RC6/TX/CK pin

(TXCKP = 0)

(TXCKP = 1)

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 19-12: SYNCHRONOUS TRANSMISSION (THROUGH TXEN)

TABLE 19-7: REGISTERS ASSOCIATED WITH SYNCHRONOUS MASTER TRANSMISSION

RC7/RX/DT pin

RC6/TX/CK pin

Write to

TXREG reg

TXIF bit

TRMT bit

bit 0 bit 1 bit 2 bit 6 bit 7

TXEN bit

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57

TXREG EUSART Transmit Register 57

TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57

BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 —WUE ABDEN 57

SPBRGH EUSART Baud Rate Generator Register High Byte 57

SPBRG EUSART Baud Rate Generator Register Low Byte 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master transmission.

Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

19.3.2 EUSART SYNCHRONOUS

MASTER RECEPTION

Once Synchronous mode is selected, reception is

enabled by setting either the Single Receive Enable bit,

SREN (RCSTA<5>), or the Continuous Receive

Enable bit, CREN (RCSTA<4>). Data is sampled on the

RX pin on the falling edge of the clock.

If enable bit SREN is set, only a single word is received.

If enable bit CREN is set, the reception is continuous

until CREN is cleared. If both bits are set, then CREN

takes precedence.

To set up a Synchronous Master Reception:

1. Initialize the SPBRGH:SPBRG registers for the

appropriate baud rate. Set or clear the BRG16

bit, as required, to achieve the desired baud rate.

2. Enable the synchronous master serial port by

setting bits, SYNC, SPEN and CSRC.

3. Ensure bits, CREN and SREN, are clear.

4. If the signal from the CK pin is to be inverted, set

the TXCKP bit.

5. If interrupts are desired, set enable bit, RCIE.

6. If 9-bit reception is desired, set bit, RX9.

7. If a single reception is required, set bit, SREN.

For continuous reception, set bit, CREN.

8. Interrupt flag bit, RCIF, will be set when reception

is complete and an interrupt will be generated if

the enable bit, RCIE, was set.

9. Read the RCSTA register to get the 9th bit (if

enabled) and determine if any error occurred

during reception.

10. Read the 8-bit received data by reading the

RCREG register.

11. If any error occurred, clear the error by clearing

bit, CREN.

12. If using interrupts, ensure that the GIE and PEIE bits

in the INTCON register (INTCON<7:6>) are set.

FIGURE 19-13: SYNCHRONOUS RECEPTION (MASTER MODE, SREN)

TABLE 19-8: REGISTERS ASSOCIATED WITH SYNCHRONOUS MASTER RECEPTION

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57

RCREG EUSART Receive Register 57

TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57

BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 —WUE ABDEN 57

SPBRGH EUSART Baud Rate Generator Register High Byte 57

SPBRG EUSART Baud Rate Generator Register Low Byte 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master reception.

Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.

CREN bit

RC7/RX/DT

RC6/TX/CK pin

Write to

bit SREN

SREN bit

RCIF bit

(Interrupt)

Read

RXREG

Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4Q2 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

‘

’

bit 0 bit 1 bit 2 bit 3 bit 4 bit 5 bit 6 bit 7

‘

’

Q1 Q2 Q3 Q4

Note: Timing diagram demonstrates Sync Master mode with bit SREN = 1 and bit BRGH = 0.

RC6/TX/CK pin

(TXCKP = 0)

(TXCKP = 1)

PIC18F2221/2321/4221/4321 FAMILY

19.4 EUSART Synchronous

Slave Mode

Synchronous Slave mode is entered by clearing bit,

CSRC (TXSTA<7>). This mode differs from the

Synchronous Master mode in that the shift clock is sup-

plied externally at the CK pin (instead of being supplied

internally in Master mode). This allows the device to

transfer or receive data while in any power-managed

mode.

19.4.1 EUSART SYNCHRONOUS

SLAVE TRANSMISSION

The operation of the Synchronous Master and Slave

modes are identical, except in the case of the Sleep

mode.

If two words are written to the TXREG and then the

SLEEP instruction is executed, the following will occur:

a) The first word will immediately transfer to the

TSR register and transmit.

b) The second word will remain in the TXREG

c) Flag bit, TXIF, will not be set.

d) When the first word has been shifted out of TSR,

the TXREG register will transfer the second word

to the TSR and flag bit, TXIF, will now be set.

e) If enable bit, TXIE, is set, the interrupt will wake

the chip from Sleep. If the global interrupt is

enabled, the program will branch to the interrupt

vector.

To set up a Synchronous Slave Transmission:

1. Enable the synchronous slave serial port by

setting bits, SYNC and SPEN, and clearing bit,

CSRC.

2. Clear bits, CREN and SREN.

3. If interrupts are desired, set enable bit, TXIE.

4. If the signal from the CK pin is to be inverted, set

the TXCKP bit.

5. If 9-bit transmission is desired, set bit, TX9.

6. Enable the transmission by setting enable bit,

TXEN.

7. If 9-bit transmission is selected, the ninth bit

should be loaded in bit TX9D.

8. Start transmission by loading data to the

TXREGx register.

9. If using interrupts, ensure that the GIE and PEIE

bits in the INTCON register (INTCON<7:6>) are

set.

TABLE 19-9: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE TRANSMISSION

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57

TXREG EUSART Transmit Register 57

TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57

BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 —WUE ABDEN 57

SPBRGH EUSART Baud Rate Generator Register High Byte 57

SPBRG EUSART Baud Rate Generator Register Low Byte 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous slave transmission.

Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

19.4.2 EUSART SYNCHRONOUS SLAVE

RECEPTION

The operation of the Synchronous Master and Slave

modes is identical, except in the case of Sleep, or any

Idle mode and bit SREN, which is a “don’t care” in

Slave mode.

If receive is enabled by setting the CREN bit prior to

entering Sleep or any Idle mode, then a word may be

received while in this low-power mode. Once the word

is received, the RSR register will transfer the data to the

RCREG register; if the RCIE enable bit is set, the

interrupt generated will wake the chip from the low-

power mode. If the global interrupt is enabled, the

program will branch to the interrupt vector.

To set up a Synchronous Slave Reception:

1. Enable the synchronous master serial port by

setting bits, SYNC and SPEN, and clearing bit,

CSRC.

2. If interrupts are desired, set enable bit RCIE.

3. If the signal from the CK pin is to be inverted, set

the TXCKP bit.

4. If 9-bit reception is desired, set bit, RX9.

5. To enable reception, set enable bit, CREN.

6. Flag bit, RCIF, will be set when reception is

complete. An interrupt will be generated if

enable bit, RCIE, was set.

7. Read the RCSTA register to get the 9th bit (if

enabled) and determine if any error occurred

during reception.

8. Read the 8-bit received data by reading the

RCREG register.

9. If any error occurred, clear the error by clearing

bit, CREN.

10. If using interrupts, ensure that the GIE and PEIE

bits in the INTCON register (INTCON<7:6>) are

set.

TABLE 19-10: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE RECEPTION

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 57

RCREG EUSART Receive Register 57

TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 57

BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 —WUE ABDEN 57

SPBRGH EUSART Baud Rate Generator Register High Byte 57

SPBRG EUSART Baud Rate Generator Register Low Byte 57

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous slave reception.

Note 1: These bits are unimplemented on 28-pin devices and read as ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

20.0 10-BIT ANALOG-TO-DIGITAL

CONVERTER (A/D) MODULE

The Analog-to-Digital (A/D) converter module has

10 inputs for the 28-pin devices and 13 for the 40/44-pin

devices. This module allows conversion of an analog

input signal to a corresponding 10-bit digital number.

The module has five registers:

• A/D Result High Register (ADRESH)

• A/D Result Low Register (ADRESL)

• A/D Control Register 0 (ADCON0)

• A/D Control Register 1 (ADCON1)

• A/D Control Register 2 (ADCON2)

The ADCON0 register, shown in Register 20-1,

controls the operation of the A/D module. The

ADCON1 register, shown in Register 20-2, configures

the functions of the port pins. The ADCON2 register,

shown in Register 20-3, configures the A/D clock

source, programmed acquisition time and justification.

U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

—— CHS3 CHS2 CHS1 CHS0 GO/DONE ADON

bit 7 bit 0

bit 7-6 Unimplemented: Read as ‘0’

bit 5-2 CHS<3:0>: Analog Channel Select bits

0000 = Channel 0 (AN0)

0001 = Channel 1 (AN1)

0010 = Channel 2 (AN2)

0011 = Channel 3 (AN3)

0100 = Channel 4 (AN4)

0101 = Channel 5 (AN5)(1,2)

0110 = Channel 6 (AN6)(1,2)

0111 = Channel 7 (AN7)(1,2)

1000 = Channel 8 (AN8)

1001 = Channel 9 (AN9)

1010 = Channel 10 (AN10)

1011 = Channel 11 (AN11)

1100 = Channel 12 (AN12

1101 = Unimplemented(2)

1110 = Unimplemented(2)

1111 = Unimplemented(2)

Note 1: These channels are not implemented on 28-pin devices.

2: Performing a conversion on unimplemented channels will return a floating input

measurement.

bit 1 GO/DONE: A/D Conversion Status bit

When ADON = 1:

1 = A/D conversion in progress

0 = A/D Idle

bit 0 ADON: A/D On bit

1 = A/D converter module is enabled

0 = A/D converter module is disabled

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

U-0 U-0 R/W-0 R/W-0 R/W-0(1) R/W(1) R/W(1) R/W(1)

—— VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0

bit 7 bit 0

bit 7-6 Unimplemented: Read as ‘0’

bit 5 VCFG1: Voltage Reference Configuration bit (VREF- source)

1 = VREF- (AN2)

0 = VSS

bit 4 VCFG0: Voltage Reference Configuration bit (VREF+ source)

1 = VREF+ (AN3)

0 = VDD

bit 3-0 PCFG<3:0>: A/D Port Configuration Control bits

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

A = Analog input D = Digital I/O

Note 1: The POR value of the PCFG bits depends on the value of the PBADEN Con-

figuration bit. When PBADEN = 1, PCFG<3:0> = 0000; when PBADEN = 0,

PCFG<3:0> = 0111.

2: AN5 through AN7 are available only on 40/44-pin devices.

PCFG<3:0>

AN12

AN11

AN10

AN9

AN8

AN7(2)

AN6(2)

AN5(2)

AN4

AN3

AN2

AN1

AN0

0000(1) AAAAAAAAAAAAA

0001 AAAAAAAAAAAAA

0010 AAAAAAAAAAAAA

0011 DAAAAAAAAAAAA

0100 DDAAAAAAAAAAA

0101 DDDAAAAAAAAAA

0110 DDDDAAAAAAAAA

0111(1) DDDDDAAAAAAAA

1000 DDDDDDAAAAAAA

1001 DDDDDDDAAAAAA

1010 DDDDDDDDAAAAA

1011 DDDDDDDDDAAAA

1100 DDDDDDDDDDAAA

1101 DDDDDDDDDDDAA

1110 DDDDDDDDDDDDA

1111 DDDDDDDDDDDDD

PIC18F2221/2321/4221/4321 FAMILY

R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

ADFM — ACQT2 ACQT1 ACQT0 ADCS2 ADCS1 ADCS0

bit 7 bit 0

bit 7 ADFM: A/D Result Format Select bit

1 = Right justified

0 = Left justified

bit 6 Unimplemented: Read as ‘0’

bit 5-3 ACQT<2:0>: A/D Acquisition Time Select bits

111 = 20 T

110 = 16 TAD

101 = 12 TAD

100 = 8 TAD

011 = 6 TAD

010 = 4 TAD

001 = 2 TAD

000 = 0 TAD(1)

bit 2-0 ADCS<2:0>: A/D Conversion Clock Select bits

111 = FRC (clock derived from A/D RC oscillator)(1)

110 = FOSC/64

101 = FOSC/16

100 = FOSC/4

011 = FRC (clock derived from A/D RC oscillator)(1)

010 = FOSC/32

001 = FOSC/8

000 = FOSC/2

Note 1: If the A/D FRC clock source is selected, a delay of one TCY (instruction cycle) is

added before the A/D clock starts. This allows the SLEEP instruction to be executed

before starting a conversion.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

The analog reference voltage is software selectable to

either the device’s positive and negative supply voltage

(VDD and VSS), or the voltage level on the RA3/AN3/

VREF+ and RA2/AN2/VREF-/CVREF pins.

The A/D converter has a unique feature of being able

to operate while the device is in Sleep mode. To

operate in Sleep, the A/D conversion clock must be

derived from the A/D’s internal RC oscillator.

The output of the sample and hold is the input into the

converter, which generates the result via successive

approximation.

A device Reset forces all registers to their Reset state.

This forces the A/D module to be turned off and any

conversion in progress is aborted.

Each port pin associated with the A/D converter can be

configured as an analog input, or as a digital I/O. The

ADRESH and ADRESL registers contain the result of

the A/D conversion. When the A/D conversion is

complete, the result is loaded into the

ADRESH:ADRESL register pair, the GO/DONE bit

(ADCON0 register) is cleared and A/D Interrupt Flag bit,

ADIF, is set. The block diagram of the A/D module is

shown in Figure 20-1.

FIGURE 20-1: A/D BLOCK DIAGRAM

(Input Voltage)

VAIN

VREF+

Reference

Voltage

VDD

VCFG<1:0>

CHS<3:0>

AN7(1)

AN6(1)

AN5(1)

AN4

AN3

AN2

AN1

AN0

0111

0110

0101

0100

0011

0010

0001

0000

10-Bit

A/D

VREF-

VSS

Converter

AN12

AN11

AN10

AN9

AN8

1100

1011

1010

1001

1000

Note 1: Channels AN5 through AN7 are not available on 28-pin devices.

2: I/O pins have diode protection to VDD and VSS.

PIC18F2221/2321/4221/4321 FAMILY

The value in the ADRESH:ADRESL registers is not

modified for a Power-on Reset. The ADRESH:ADRESL

registers will contain unknown data after a Power-on

Reset.

After the A/D module has been configured as desired,

the selected channel must be acquired before the

conversion is started. The analog input channels must

have their corresponding TRIS bits selected as an

input. To determine acquisition time, see Section 20.1

“A/D Acquisition Requirements”. After this acquisi-

tion time has elapsed, the A/D conversion can be

started. An acquisition time can be programmed to

occur between setting the GO/DONE bit and the actual

start of the conversion.

The following steps should be followed to perform an A/D

conversion:

1. Configure the A/D module:

• Configure analog pins, voltage reference and

digital I/O (ADCON1)

• Select A/D input channel (ADCON0)

• Select A/D acquisition time (ADCON2)

• Select A/D conversion clock (ADCON2)

• Turn on A/D module (ADCON0)

2. Configure A/D interrupt (if desired):

• Clear ADIF bit

• Set ADIE bit

• Set GIE bit

3. Wait the required acquisition time (if required).

4. Start conversion:

• Set GO/DONE bit (ADCON0 register)

5. Wait for A/D conversion to complete, by either:

• Polling for the GO/DONE bit to be cleared

• Waiting for the A/D interrupt

6. Read A/D Result registers (ADRESH:ADRESL);

clear bit ADIF, if required.

7. For next conversion, go to step 1 or step 2, as

required. The A/D conversion time per bit is

defined as T

AD. A minimum wait of 2 TAD is

required before the next acquisition starts.

FIGURE 20-2: A/D TRANSFER FUNCTION

FIGURE 20-3: ANALOG INPUT MODEL

Digital Code Output

3FEh

003h

002h

001h

000h

0.5 LSB

1 LSB

1.5 LSB

2 LSB

2.5 LSB

1022 LSB

1022.5 LSB

3 LSB

Analog Input Voltage

3FFh

1023 LSB

1023.5 LSB

VAIN CPIN

Rs ANx

5 pF

VT = 0.6V

VT = 0.6V ILEAKAGE

RIC ≤ 1k

Sampling

Switch

SS RSS

CHOLD = 25 pF

VSS

VDD

±100 nA

Legend: CPIN

ILEAKAGE

RIC

CHOLD

= Input Capacitance

= Threshold Voltage

= Leakage Current at the pin due to

= Interconnect Resistance

= Sampling Switch

= Sample/Hold Capacitance (from DAC)

various junctions

= Sampling Switch ResistanceRSS

VDD

Sampling Switch

1234

(kΩ)

PIC18F2221/2321/4221/4321 FAMILY

20.1 A/D Acquisition Requirements

For the A/D converter to meet its specified accuracy,

the charge holding capacitor (CHOLD) must be allowed

to fully charge to the input channel voltage level. The

analog input model is shown in Figure 20-3. The

source impedance (RS) and the internal sampling

switch (RSS) impedance directly affect the time

required to charge the capacitor CHOLD. The sampling

switch (RSS) impedance varies over the device voltage

(VDD). The source impedance affects the offset voltage

at the analog input (due to pin leakage current). The

maximum recommended impedance for analog

sources is 2.5 kΩ. After the analog input channel is

selected (changed), the channel must be sampled for

at least the minimum acquisition time before starting a

conversion.

To calculate the minimum acquisition time,

Equation 20-1 may be used. This equation assumes

that 1/2 LSb error is used (1024 steps for the A/D). The

1/2 LSb error is the maximum error allowed for the A/D

to meet its specified resolution.

Example 20-3 shows the calculation of the minimum

required acquisition time TACQ. This calculation is

based on the following application system

assumptions:

CHOLD = 25 pF

Rs = 2.5 kΩ

Conversion Error ≤1/2 LSb

VDD =5V → Rss = 2 kΩ

Temperature = 85°C (system max.)

EQUATION 20-1: ACQUISITION TIME

EQUATION 20-2: A/D MINIMUM CHARGING TIME

EQUATION 20-3: CALCULATING THE MINIMUM REQUIRED ACQUISITION TIME

Note: When the conversion is started, the

holding capacitor is disconnected from the

input pin.

TACQ = Amplifier Settling Time + Holding Capacitor Charging Time + Temperature Coefficient

AMP + TC + TCOFF

VHOLD = (VREF – (VREF/2048)) • (1 – e(-TC/CHOLD(RIC + RSS + RS)))

TC = -(CHOLD)(RIC + RSS + RS) ln(1/2048)

TACQ =TAMP + TC + TCOFF

TAMP =0.2 μs

TCOFF = (Temp – 25°C)(0.02 μs/°C)

(85°C – 25°C)(0.02 μs/°C)

1.2 μs

Temperature coefficient is only required for temperatures > 25°C. Below 25°C, TCOFF = 0 ms.

TC = -(CHOLD)(RIC + RSS + RS) ln(1/2047)

-(25 pF) (1 kΩ + 2 kΩ + 2.5 kΩ) ln(0.0004883)

1.05 μs

TACQ =0.2 μs + 1 μs + 1.2 μs

2.4 μs

PIC18F2221/2321/4221/4321 FAMILY

20.2 Selecting and Configuring

Acquisition Time

The ADCON2 register allows the user to select an

acquisition time that occurs each time the GO/DONE

bit is set. It also gives users the option to use an

automatically determined acquisition time.

Acquisition time may be set with the ACQT<2:0> bits

(ADCON2<5:3>), which provides a range of 2 to

20 TAD. When the GO/DONE bit is set, the A/D module

continues to sample the input for the selected acquisi-

tion time, then automatically begins a conversion.

Since the acquisition time is programmed, there may

be no need to wait for an acquisition time between

selecting a channel and setting the GO/DONE bit.

Manual acquisition is selected when

ACQT<2:0> = 000. When the GO/DONE bit is set,

sampling is stopped and a conversion begins. The user

is responsible for ensuring the required acquisition time

has passed between selecting the desired input

channel and setting the GO/DONE bit. This option is

also the default Reset state of the ACQT<2:0> bits and

is compatible with devices that do not offer

programmable acquisition times.

In either case, when the conversion is completed, the

GO/DONE bit is cleared, the ADIF flag is set and the

A/D begins sampling the currently selected channel

again. If an acquisition time is programmed, there is

nothing to indicate if the acquisition time has ended or

if the conversion has begun.

20.3 Selecting the A/D Conversion

Clock

The A/D conversion time per bit is defined as TAD. The

A/D conversion requires 11 TAD per 10-bit conversion.

The source of the A/D conversion clock is software

selectable. There are seven possible options for T

AD:

•2 T

OSC

•4 TOSC

•8 TOSC

•16 TOSC

•32 TOSC

•64 TOSC

• Internal RC Oscillator

For correct A/D conversions, the A/D conversion clock

AD) must be as short as possible, but greater than the

minimum TAD (see parameter 130 for more

information).

Table 20-1 shows the resultant T

AD times derived from

the device operating frequencies and the A/D clock

source selected.

TABLE 20-1: TAD vs. DEVICE OPERATING FREQUENCIES

AD Clock Source (TAD) Maximum Device Frequency

Operation ADCS<2:0> PIC18F2X21/4X21 PIC18LF2X21/4X21(4)

2 T

OSC 000 2.86 MHz 1.43 kHz

4 TOSC 100 5.71 MHz 2.86 MHz

8 T

OSC 001 11.43 MHz 5.72 MHz

16 TOSC 101 22.86 MHz 11.43 MHz

32 T

OSC 010 40.0 MHz 22.86 MHz

64 T

OSC 110 40.0 MHz 22.86 MHz

RC(3) x11 1.00 MHz(1) 1.00 MHz(2)

Note 1: The RC source has a typical TAD time of 1.2 μs.

2: The RC source has a typical TAD time of 2.5 μs.

3: For device frequencies above 1 MHz, the device must be in Sleep for the entire conversion or the A/D

accuracy may be out of specification.

4: Low-power (PIC18LFXXXX) devices only.

PIC18F2221/2321/4221/4321 FAMILY

20.4 Operation in Power-Managed

Modes

The selection of the automatic acquisition time and A/D

conversion clock is determined in part by the clock

source and frequency while in a power-managed mode.

If the A/D is expected to operate while the device is in

a power-managed mode, the ACQT<2:0> and

ADCS<2:0> bits in ADCON2 should be updated in

accordance with the clock source to be used in that

mode. After entering the mode, an A/D acquisition or

conversion may be started. Once started, the device

should continue to be clocked by the same clock

source until the conversion has been completed.

If desired, the device may be placed into the

corresponding Idle mode during the conversion. If the

device clock frequency is less than 1 MHz, the A/D RC

clock source should be selected.

Operation in Sleep mode requires the A/D FRC clock to

be selected. If bits ACQT<2:0> are set to ‘000’ and a

conversion is started, the conversion will be delayed

one instruction cycle to allow execution of the SLEEP

instruction and entry to Sleep mode. The IDLEN bit

(OSCCON<7>) must have already been cleared prior

to starting the conversion.

20.5 Configuring Analog Port Pins

The ADCON1, TRISA, TRISB and TRISE registers all

configure the A/D port pins. The port pins needed as

analog inputs must have their corresponding TRIS bits

set (input). If the TRIS bit is cleared (output), the digital

output level (VOH or VOL) will be converted.

The A/D operation is independent of the state of the

CHS<3:0> bits and the TRIS bits.

Note 1: When reading the Port register, all pins

configured as analog input channels will

read as cleared (a low level). Pins

configured as digital inputs will convert as

analog inputs. Analog levels on a digitally

configured input will be accurately

converted.

2: Analog levels on any pin defined as a

digital input may cause the digital input

buffer to consume current out of the

device’s specification limits.

3: The PBADEN bit in Configuration

reset as analog or digital pins by control-

ling how the PCFG<3:0> bits in ADCON1

are reset.

PIC18F2221/2321/4221/4321 FAMILY

20.6 A/D Conversions

Figure 20-4 shows the operation of the A/D converter

after the GO/DONE bit has been set and the

ACQT<2:0> bits are cleared. A conversion is started

after the following instruction to allow entry into Sleep

mode before the conversion begins.

Figure 20-5 shows the operation of the A/D converter

after the GO/DONE bit has been set and the

ACQT<2:0> bits are set to ‘010’ and selecting a 4 TAD

acquisition time before the conversion starts.

Clearing the GO/DONE bit during a conversion will abort

the current conversion. The A/D Result register pair will

NOT be updated with the partially completed A/D

conversion sample. This means the ADRESH:ADRESL

registers will continue to contain the value of the last

completed conversion (or the last value written to the

ADRESH:ADRESL registers).

After the A/D conversion is completed or aborted, a

AD wait is required before the next acquisition can be

started. After this wait, acquisition on the selected

channel is automatically started.

20.7 Discharge

The discharge phase is used to initialize the value of

the capacitor array. The array is discharged before

every sample. This feature helps to optimize the unity-

gain amplifier, as the circuit always needs to charge the

capacitor array, rather than charge/discharge based on

previous measure values.

FIGURE 20-4: A/D CONVERSION TAD CYCLES (ACQT<2:0> = 000, TACQ = 0)

FIGURE 20-5: A/D CONVERSION TAD CYCLES (ACQT<2:0> = 010, TACQ = 4 TAD)

Note: The GO/DONE bit should NOT be set in

the same instruction that turns on the A/D.

TAD1TAD2TAD3TAD4 TAD5TAD6 TAD7TAD8 TAD11

Set GO/DONE bit

Holding capacitor is disconnected from analog input (typically 100 ns)

TAD9 TAD10

TCY - TAD

ADRESH:ADRESL is loaded, GO/DONE bit is cleared,

ADIF bit is set, holding capacitor is connected to analog input.

Conversion starts

b9 b6 b5 b4 b3 b2 b1

b8 b7

On the following cycle:

TAD1

Discharge

123 4 5 67811

Set GO/DONE bit

(Holding capacitor is disconnected)

910

Conversion starts

123 4

(Holding capacitor continues

acquiring input)

TACQT Cycles TAD Cycles

Automatic

Acquisition

Time

b0b9 b6 b5 b4 b3 b2 b1

b8 b7

ADRESH:ADRESL is loaded, GO/DONE bit is cleared,

ADIF bit is set, holding capacitor is connected to analog input.

On the following cycle:

TAD1

Discharge

PIC18F2221/2321/4221/4321 FAMILY

20.8 Use of the CCP2 Trigger

An A/D conversion can be started by the Special Event

Trigger of the CCP2 module. This requires that the

CCP2M<3:0> bits (CCP2CON<3:0>) be programmed

as ‘1011’ and that the A/D module is enabled (ADON

bit is set). When the trigger occurs, the GO/DONE bit

will be set, starting the A/D acquisition and conversion

and the Timer1 (or Timer3) counter will be reset to zero.

Timer1 (or Timer3) is reset to automatically repeat the

A/D acquisition period with minimal software overhead

(moving ADRESH:ADRESL to the desired location).

The appropriate analog input channel must be selected

and the minimum acquisition period is either timed by

the user, or an appropriate TACQ time selected before

the Special Event Trigger sets the GO/DONE bit (starts

a conversion).

If the A/D module is not enabled (ADON is cleared), the

Special Event Trigger will be ignored by the A/D module

but will still reset the Timer1 (or Timer3) counter.

TABLE 20-2: REGISTERS ASSOCIATED WITH A/D OPERATION

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 58

PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 58

IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 58

PIR2 OSCFIF CMIF —EEIF BCLIF HLVDIF TMR3IF CCP2IF 58

PIE2 OSCFIE CMIE —EEIE BCLIE HLVDIE TMR3IE CCP2IE 58

IPR2 OSCFIP CMIP —EEIP BCLIP HLVDIP TMR3IP CCP2IP 58

ADRESH A/D Result Register High Byte 57

ADRESL A/D Result Register Low Byte 57

ADCON0 —— CHS3 CHS2 CHS1 CHS0 GO/DONE ADON 57

ADCON1 —— VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 57

ADCON2 ADFM — ACQT2 ACQT1 ACQT0 ADCS2 ADCS1 ADCS0 57

PORTA RA7(2) RA6(2) RA5 RA4 RA3 RA2 RA1 RA0 58

TRISA TRISA7(2) TRISA6(2) PORTA Data Direction Control Register 58

PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 58

TRISB PORTB Data Direction Control Register 58

LATB PORTB Data Latch Register (Read and Write to Data Latch) 58

PORTE — — — —RE3

(3) RE2(1) RE1(1) RE0(1) 58

TRISE(1) IBF OBF IBOV PSPMODE — TRISE2 TRISE1 TRISE0 58

LATE(1) — — — — — PORTE Data Latch Register 58

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for A/D conversion.

Note 1: These registers and/or bits are unimplemented on 28-pin devices and are read as ‘0’.

2: PORTA<7:6> and their direction bits are individually configured as port pins based on various primary

oscillator modes. When disabled, these bits read as ‘0’.

3: RE3 port bit is available only as an input pin when the MCLRE Configuration bit is ‘0’.

PIC18F2221/2321/4221/4321 FAMILY

21.0 COMPARATOR MODULE

The analog comparator module contains two

comparators that can be configured in a variety of

ways. The inputs can be selected from the analog

inputs multiplexed with pins RA0 through RA5, as well

as the on-chip voltage reference (see Section 22.0

“Comparator Voltage Reference Module”). The digi-

tal outputs (normal or inverted) are available at the pin

level and can also be read through the control register.

The CMCON register (Register 21-1) selects the

comparator input and output configuration. Block

diagrams of the various comparator configurations are

shown in Figure 21-1.

R-0 R-0 R/W-0 R/W-0 R/W-0 R/W-1 R/W-1 R/W-1

C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0

bit 7 bit 0

bit 7 C2OUT: Comparator 2 Output bit

When C2INV = 0:

1 = C2 VIN+ > C2 VIN-

0 = C2 VIN+ < C2 VIN-

When C2INV = 1:

1 = C2 VIN+ < C2 VIN-

0 = C2 VIN+ > C2 VIN-

bit 6 C1OUT: Comparator 1 Output bit

When C1INV = 0:

1 = C1 VIN+ > C1 VIN-

0 = C1 VIN+ < C1 VIN-

When C1INV = 1:

1 = C1 VIN+ < C1 VIN-

0 = C1 VIN+ > C1 VIN-

bit 5 C2INV: Comparator 2 Output Inversion bit

1 = C2 output inverted

0 = C2 output not inverted

bit 4 C1INV: Comparator 1 Output Inversion bit

1 = C1 output inverted

0 = C1 output not inverted

bit 3 CIS: Comparator Input Switch bit

When CM<2:0> = 110:

1 =C1 VIN- connects to RA3/AN3/VREF+

C2 VIN- connects to RA2/AN2/VREF-/CVREF

0 =C1 VIN- connects to RA0/AN0

C2 VIN- connects to RA1/AN1

bit 2-0 CM<2:0>: Comparator Mode bits

Figure 21-1 shows the Comparator modes and the CM<2:0> bit settings.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

21.1 Comparator Configuration

There are eight modes of operation for the comparators,

shown in Figure 21-1. Bits CM<2:0> of the CMCON

ister controls the data direction of the comparator pins

for each mode. If the Comparator mode is changed, the

comparator output level may not be valid for the

specified mode change delay shown in Section 27.0

“Electrical Characteristics”.

FIGURE 21-1: COMPARATOR I/O OPERATING MODES

Note: Comparator interrupts should be disabled

during a Comparator mode change;

otherwise, a false interrupt may occur.

RA0/AN0 VIN-

VIN+

RA3/AN3/ Off (Read as ‘0’)

Comparators Reset

CM<2:0> = 000

RA1/AN1 VIN-

VIN+

RA2/AN2/ Off (Read as ‘0’)

VIN-

VIN+C1OUT

Two Independent Comparators

CM<2:0> = 010

VIN-

VIN+C2OUT

VIN-

VIN+C1OUT

Two Common Reference Comparators

CM<2:0> = 100

VIN-

VIN+C2OUT

VIN-

VIN+Off (Read as ‘0’)

One Independent Comparator with Output

CM<2:0> = 001

VIN-

VIN+C1OUT

VIN-

VIN+Off (Read as ‘0’)

Comparators Off (POR Default Value)

CM<2:0> = 111

VIN-

VIN+Off (Read as ‘0’)

VIN-

VIN+C1OUT

Four Inputs Multiplexed to Two Comparators

CM<2:0> = 110

VIN-

VIN+C2OUT

From VREF Module

CIS = 0

CIS = 1

CIS = 0

CIS = 1

VIN-

VIN+C1OUT

Two Common Reference Comparators with Outputs

CM<2:0> = 101

VIN-

VIN+C2OUT

A = Analog Input, port reads zeros always D = Digital Input CIS (CMCON<3>) is the Comparator Input Switch

CVREF

VIN-

VIN+C1OUT

Two Independent Comparators with Outputs

CM<2:0> = 011

VIN-

VIN+C2OUT

RA5/AN4/SS/HLVDIN/C2OUT*

RA4/T0CKI/C1OUT*

VREF+

VREF-/CVREF

RA0/AN0

RA3/AN3/

RA1/AN1

RA2/AN2/

VREF+

VREF-/CVREF

RA0/AN0

RA3/AN3/

RA1/AN1

RA2/AN2/

VREF+

VREF-/CVREF

RA0/AN0

RA3/AN3/

RA1/AN1

RA2/AN2/

VREF+

VREF-/CVREF

RA0/AN0

RA3/AN3/

RA1/AN1

RA2/AN2/

VREF+

VREF-/CVREF

RA0/AN0

RA3/AN3/

RA1/AN1

RA2/AN2/

VREF+

VREF-/CVREF

RA0/AN0

RA3/AN3/

VREF+

RA1/AN1

RA2/AN2/

VREF-/CVREF

RA4/T0CKI/C1OUT*

RA5/AN4/SS/HLVDIN/C2OUT*

RA0/AN0

RA3/AN3/

VREF+

RA1/AN1

RA2/AN2/

VREF-/CVREF

RA4/T0CKI/C1OUT*

* Setting the TRISA<5:4> bits will disable the comparator outputs by configuring the pins as inputs.

PIC18F2221/2321/4221/4321 FAMILY

21.2 Comparator Operation

A single comparator is shown in Figure 21-2, along with

the relationship between the analog input levels and

the digital output. When the analog input at VIN+ is less

than the analog input VIN-, the output of the comparator

is a digital low level. When the analog input at VIN+ is

greater than the analog input VIN-, the output of the

comparator is a digital high level. The shaded areas of

the output of the comparator in Figure 21-2 represent

the uncertainty, due to input offsets and response time.

21.3 Comparator Reference

Depending on the comparator operating mode, either

an external or internal voltage reference may be used.

The analog signal present at VIN- is compared to the

signal at VIN+ and the digital output of the comparator

is adjusted accordingly (Figure 21-2).

FIGURE 21-2: SINGLE COMPARATOR

21.3.1 EXTERNAL REFERENCE SIGNAL

When external voltage references are used, the

comparator module can be configured to have the

comparators operate from the same or different

reference sources. However, threshold detector

applications may require the same reference. The

reference signal must be between VSS and VDD and

can be applied to either pin of the comparator(s).

21.3.2 INTERNAL REFERENCE SIGNAL

The comparator module also allows the selection of an

internally generated voltage reference from the

comparator voltage reference module. This module is

described in more detail in Section 22.0 “Comparator

Voltage Reference Module”.

The internal reference is only available in the mode

where four inputs are multiplexed to two comparators

(CM<2:0> = 110). In this mode, the internal voltage ref-

erence is applied to the VIN+ pin of both comparators.

21.4 Comparator Response Time

Response time is the minimum time, after selecting a

new reference voltage or input source, before the

comparator output has a valid level. If the internal ref-

erence is changed, the maximum delay of the internal

voltage reference must be considered when using the

comparator outputs. Otherwise, the maximum delay of

the comparators should be used (see Section 27.0

“Electrical Characteristics”).

21.5 Comparator Outputs

The comparator outputs are read through the CMCON

outputs may also be directly output to the RA4 and RA5

I/O pins. When enabled, multiplexors in the output path

of the RA4 and RA5 pins will switch and the output of

each pin will be the unsynchronized output of the

comparator. The uncertainty of each of the

comparators is related to the input offset voltage and

the response time given in the specifications.

Figure 21-3 shows the comparator output block

diagram.

The TRISA bits will still function as an output enable/

disable for the RA4 and RA5 pins while in this mode.

The polarity of the comparator outputs can be changed

using the C2INV and C1INV bits (CMCON<5:4>).

–

VIN+

VIN-

Output

VIN-

VIN+

Note 1: When reading the Port register, all pins

configured as analog inputs will read as a

‘0’. Pins configured as digital inputs will

convert an analog input according to the

Schmitt Trigger input specification.

2: Analog levels on any pin defined as a

digital input may cause the input buffer to

consume more current than is specified.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 21-3: COMPARATOR OUTPUT BLOCK DIAGRAM

21.6 Comparator Interrupts

The comparator interrupt flag is set whenever there is

a change in the output value of either comparator.

Software will need to maintain information about the

status of the output bits, as read from CMCON<7:6>, to

determine the actual change that occurred. The CMIF

bit (PIR2<6>) is the Comparator Interrupt Flag. The

CMIF bit must be reset by clearing it. Since it is also

possible to write a ‘1’ to this register, a simulated

interrupt may be initiated.

Both the CMIE bit (PIE2<6>) and the PEIE bit

(INTCON<6>) must be set to enable the interrupt. In

addition, the GIE bit (INTCON<7>) must also be set. If

any of these bits are clear, the interrupt is not enabled,

though the CMIF bit will still be set if an interrupt

condition occurs.

The user, in the Interrupt Service Routine, can clear the

interrupt in the following manner:

a) Any read or write of CMCON will end the

mismatch condition.

b) Clear flag bit CMIF.

A mismatch condition will continue to set flag bit CMIF.

Reading CMCON will end the mismatch condition and

allow flag bit CMIF to be cleared.

21.7 Comparator Operation

During Sleep

When a comparator is active and the device is placed

in Sleep mode, the comparator remains active and the

interrupt is functional if enabled. This interrupt will

wake-up the device from Sleep mode, when enabled.

Each operational comparator will consume additional

current, as shown in the comparator specifications. To

minimize power consumption while in Sleep mode, turn

off the comparators (CM<2:0> = 111) before entering

Sleep. If the device wakes up from Sleep, the contents

of the CMCON register are not affected.

21.8 Effects of a Reset

A device Reset forces the CMCON register to its Reset

state, causing the comparator modules to be turned off

(CM<2:0> = 111). However, the input pins (RA0

through RA3) are configured as analog inputs by

default on device Reset. The I/O configuration for these

pins is determined by the setting of the PCFG<3:0> bits

(ADCON1<3:0>). Therefore, device current is

minimized when analog inputs are present at Reset

time.

To RA4 or

RA5 pin

Bus

Data

Set

MULTIPLEX

CMIF

bit

Port Pins

Read CMCON

Reset

From

Other

Comparator

CxINV

EN CL

Note: If a change in the CMCON register

(C1OUT or C2OUT) should occur when a

read operation is being executed (start of

the Q2 cycle), then the CMIF (PIR2

PIC18F2221/2321/4221/4321 FAMILY

21.9 Analog Input Connection

Considerations

A simplified circuit for an analog input is shown in

Figure 21-4. Since the analog pins are connected to a

digital output, they have reverse biased diodes to VDD

and VSS. The analog input, therefore, must be between

VSS and VDD. If the input voltage deviates from this

range by more than 0.6V in either direction, one of the

diodes is forward biased and a latch-up condition may

occur. A maximum source impedance of 10 kΩ is

recommended for the analog sources. Any external

component connected to an analog input pin, such as

a capacitor or a Zener diode, should have very little

leakage current.

FIGURE 21-4: COMPARATOR ANALOG INPUT MODEL

TABLE 21-1: REGISTERS ASSOCIATED WITH COMPARATOR MODULE

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 57

CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 57

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 58

PIR2 OSCFIF CMIF — EEIF BCLIF HLVDIF TMR3IF CCP2IF 58

PIE2 OSCFIE CMIE —EEIE BCLIE HLVDIE TMR3IE CCP2IE 58

IPR2 OSCFIP CMIP —EEIP BCLIP HLVDIP TMR3IP CCP2IP 58

PORTA RA7(1) RA6(1) RA5 RA4 RA3 RA2 RA1 RA0 58

LATA LATA7(1) LATA6(1) PORTA Data Latch Register (Read and Write to Data Latch) 58

TRISA TRISA7(1) TRISA6(1) PORTA Data Direction Control Register 58

Legend: — = unimplemented, read as ‘0’. Shaded cells are unused by the comparator module.

Note 1: PORTA<7:6> and their direction and latch bits are individually configured as port pins based on various

primary oscillator modes. When disabled, these bits read as ‘0’.

RS < 10k

AIN

CPIN

5 pF

VDD

VT = 0.6V

RIC

ILEAKAGE

±100 nA

VSS

Legend: CPIN = Input Capacitance

VT= Threshold Voltage

ILEAKAGE = Leakage Current at the pin due to various junctions

RIC = Interconnect Resistance

RS= Source Impedance

VA = Analog Voltage

Comparator

Input

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

22.0 COMPARATOR VOLTAGE

REFERENCE MODULE

The comparator voltage reference is a 16-tap resistor

ladder network that provides a selectable reference

voltage. Although its primary purpose is to provide a

reference for the analog comparators, it may also be

used independently of them.

A block diagram of the module is shown in Figure 22-1.

The resistor ladder is segmented to provide two ranges

of CVREF values and has a power-down function to

conserve power when the reference is not being used.

The module’s supply reference can be provided from

either device VDD/VSS or an external voltage reference.

22.1 Configuring the Comparator

Voltage Reference

The voltage reference module is controlled through the

CVRCON register (Register 22-1). The comparator

voltage reference provides two ranges of output

voltage, each with 16 distinct levels. The range to be

used is selected by the CVRR bit (CVRCON<5>). The

primary difference between the ranges is the size of the

steps selected by the CVREF selection bits

(CVR<3:0>), with one range offering finer resolution.

The equations used to calculate the output of the

comparator voltage reference are as follows:

If CVRR = 1:

CVREF = ((CVR<3:0>)/24) x CVRSRC

If CVRR = 0:

CVREF = (CVRSRC x 1/4) + (((CVR<3:0>)/32) x

CVRSRC)

The comparator reference supply voltage can come

from either VDD and VSS, or the external VREF+ and

VREF- that are multiplexed with RA2 and RA3. The

voltage source is selected by the CVRSS bit

(CVRCON<4>).

The settling time of the comparator voltage reference

must be considered when changing the CVREF

output (see Table 27-3 in Section 27.0 “Electrical

Characteristics”).

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

CVREN CVROE(1) CVRR CVRSS CVR3 CVR2 CVR1 CVR0

bit 7 bit 0

bit 7 CVREN: Comparator Voltage Reference Enable bit

1 =CV

REF circuit powered on

0 =CV

REF circuit powered down

bit 6 CVROE: Comparator VREF Output Enable bit(1)

1 =CVREF voltage level is also output on the RA2/AN2/VREF-/CVREF pin

0 =CV

REF voltage is disconnected from the RA2/AN2/VREF-/CVREF pin

Note 1: CVROE overrides the TRISA<2> bit setting.

bit 5 CVRR: Comparator VREF Range Selection bit

1 = 0.00 CVRSRC to 0.667 CVRSRC, with CVRSRC/24 step size (low range)

0 = 0.25 CVRSRC to 0.75 CVRSRC, with CVRSRC/32 step size (high range)

bit 4 CVRSS: Comparator VREF Source Selection bit

1 = Comparator reference source, CVRSRC = (VREF+) – (VREF-)

0 = Comparator reference source, CVRSRC = VDD – VSS

bit 3-0 CVR<3:0>: Comparator VREF Value Selection bits (0 ≤ (CVR<3:0>) ≤ 15)

When CVRR = 1:

CVREF = ((CVR<3:0>)/24) • (CVRSRC)

When CVRR = 0:

CVREF = (CVRSRC/4) + ((CVR<3:0>)/32) • (CVRSRC)

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 22-1: COMPARATOR VOLTAGE REFERENCE BLOCK DIAGRAM

22.2 Voltage Reference Accuracy/Error

The full range of voltage reference cannot be realized

due to the construction of the module. The transistors

on the top and bottom of the resistor ladder network

(Figure 22-1) keep CVREF from approaching the

reference source rails. The voltage reference is derived

from the reference source; therefore, the CVREF output

changes with fluctuations in that source. The tested

absolute accuracy of the voltage reference can be

found in Section 27.0 “Electrical Characteristics”.

22.3 Operation During Sleep

When the device wakes up from Sleep through an

interrupt or a Watchdog Timer time-out, the contents of

the CVRCON register are not affected. To minimize

current consumption in Sleep mode, the voltage

reference should be disabled.

22.4 Effects of a Reset

A device Reset disables the voltage reference by

clearing bit, CVREN (CVRCON<7>). This Reset also

disconnects the reference from the RA2 pin by clearing

bit, CVROE (CVRCON<6>) and selects the high-voltage

range by clearing bit, CVRR (CVRCON<5>). The CVR

value select bits are also cleared.

22.5 Connection Considerations

The voltage reference module operates independently

of the comparator module. The output of the reference

generator may be connected to the RA2 pin if the

CVROE bit is set. Enabling the voltage reference

output onto RA2 when it is configured as a digital input

will increase current consumption. Connecting RA2 as

a digital output with CVRSS enabled will also increase

current consumption.

The RA2 pin can be used as a simple D/A output with

limited drive capability. Due to the limited current drive

capability, a buffer must be used on the voltage

reference output for external connections to VREF.

Figure 22-2 shows an example buffering technique.

16-to-1 MUX

CVR<3:0>

CVREN

CVRSS = 0

VDD

VREF+CVRSS = 1

CVRSS = 0

VREF-CVRSS = 1

16 Steps

CVRR

CVREF

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 22-2: COMPARATOR VOLTAGE REFERENCE OUTPUT BUFFER EXAMPLE

TABLE 22-1: REGISTERS ASSOCIATED WITH COMPARATOR VOLTAGE REFERENCE

CVREF Output

–

CVREF

Module

Voltage

Reference

Output

Impedance

R(1)

RA2

Note 1: R is dependent upon the voltage reference configuration bits, CVRCON<3:0> and CVRCON<5>.

PIC18FXXXX

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 57

CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 57

TRISA TRISA7(1) TRISA6(1) PORTA Data Direction Control Register 58

Legend: Shaded cells are not used with the comparator voltage reference.

Note 1: PORTA pins are enabled based on oscillator configuration.

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

23.0 HIGH/LOW-VOLTAGE DETECT

(HLVD)

PIC18F2221/2321/4221/4321 family devices have a

High/Low-Voltage Detect module (HLVD). This is a

programmable circuit that allows the user to specify both

a device voltage trip point and the direction of change

from that point. If the device experiences an excursion

past the trip point in that direction, an interrupt flag is set.

If the interrupt is enabled, the program execution will

branch to the interrupt vector address and the software

can then respond to the interrupt.

The High/Low-Voltage Detect Control register

(Register 23-1) completely controls the operation of the

HLVD module. This allows the circuitry to be “turned

off” by the user under software control, which

minimizes the current consumption for the device.

The block diagram for the HLVD module is shown in

Figure 23-1.

The module is enabled by setting the HLVDEN bit.

Each time that the HLVD module is enabled, the

circuitry requires some time to stabilize. The IRVST bit

is a read-only bit and is used to indicate when the circuit

is stable. The module can only generate an interrupt

after the circuit is stable and IRVST is set.

The VDIRMAG bit determines the overall operation of

the module. When VDIRMAG is cleared, the module

monitors for drops in VDD below a predetermined set

point. When the bit is set, the module monitors for rises

in VDD above the set point.

R/W-0 U-0 R-0 R/W-0 R/W-0 R/W-1 R/W-0 R/W-1

VDIRMAG — IRVST HLVDEN HLVDL3 HLVDL2 HLVDL1 HLVDL0

bit 7 bit 0

bit 7 VDIRMAG: Voltage Direction Magnitude Select bit

1 = Event occurs when voltage equals or exceeds trip point (HLVDL<3:0>)

0 = Event occurs when voltage equals or falls below trip point (HLVDL<3:0>)

bit 6 Unimplemented: Read as ‘0’

bit 5 IRVST: Internal Reference Voltage Stable Flag bit

1 = Indicates that the voltage detect logic will generate the interrupt flag at the specified voltage

range

0 = Indicates that the voltage detect logic will not generate the interrupt flag at the specified

voltage range and the HLVD interrupt should not be enabled

bit 4 HLVDEN: High/Low-Voltage Detect Power Enable bit

1 = HLVD enabled

0 = HLVD disabled

bit 3-0 HLVDL<3:0>: Voltage Detection Limit bits

1111 = External analog input is used (input comes from the HLVDIN pin)

1110 = Maximum setting

0000 = Minimum setting

Note: See Table 27-4 in Section 27.0 “Electrical Characteristics” for the specifications.

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC18F2221/2321/4221/4321 FAMILY

23.1 Operation

When the HLVD module is enabled, a comparator uses

an internally generated reference voltage as the set

point. The set point is compared with the trip point,

where each node in the resistor divider represents a

trip point voltage. The “trip point” voltage is the voltage

level at which the device detects a high or low-voltage

event, depending on the configuration of the module.

When the supply voltage is equal to the trip point, the

voltage tapped off of the resistor array is equal to the

internal reference voltage generated by the voltage

reference module. The comparator then generates an

interrupt signal by setting the HLVDIF bit.

The trip point voltage is software programmable to

any one of 16 values. The trip point is selected by

programming the HLVDL<3:0> bits (HLVDCON<3:0>).

The HLVD module has an additional feature that allows

the user to supply the trip voltage to the module from an

external source. This mode is enabled when bits

HLVDL<3:0> are set to ‘1111’. In this state, the

comparator input is multiplexed from the external input

pin, HLVDIN. This gives users flexibility because it

allows them to configure the High/Low-Voltage Detect

interrupt to occur at any voltage in the valid operating

range.

FIGURE 23-1: HLVD MODULE BLOCK DIAGRAM (WITH EXTERNAL INPUT)

Set

VDD

16-to-1 MUX

HLVDEN

HLVDCON

HLVDIN

HLVDL<3:0>

HLVDIN

VDD

Externally Generated

Trip Point

HLVDIF

HLVDEN

BOREN

Internal Voltage

Reference

VDIRMAG

PIC18F2221/2321/4221/4321 FAMILY

23.2 HLVD Setup

The following steps are needed to set up the HLVD

module:

1. Disable the module by clearing the HLVDEN bit

(HLVDCON<4>).

2. Write the value to the HLVDL<3:0> bits that

selects the desired HLVD trip point.

3. Set the VDIRMAG bit to detect high voltage

(VDIRMAG = 1) or low voltage (VDIRMAG = 0).

4. Enable the HLVD module by setting the

HLVDEN bit.

5. Clear the HLVD interrupt flag (PIR2<2>), which

may have been set from a previous interrupt.

6. Enable the HLVD interrupt if interrupts are

desired by setting the HLVDIE and GIE bits

(PIE<2> and INTCON<7>). An interrupt will not

be generated until the IRVST bit is set.

23.3 Current Consumption

When the module is enabled, the HLVD comparator

and voltage divider are enabled and will consume static

current. The total current consumption, when enabled,

is specified in electrical specification parameter D022B.

Depending on the application, the HLVD module does

not need to be operating constantly. To decrease the

current requirements, the HLVD circuitry may only

need to be enabled for short periods where the voltage

is checked. After doing the check, the HLVD module

may be disabled.

23.4 HLVD Start-up Time

The internal reference voltage of the HLVD module,

specified in electrical specification parameter D420,

may be used by other internal circuitry, such as the

Programmable Brown-out Reset. If the HLVD or other

circuits using the voltage reference are disabled to

lower the device’s current consumption, the reference

voltage circuit will require time to become stable before

a low or high-voltage condition can be reliably

detected. This start-up time, TIRVST, is an interval that

is independent of device clock speed. It is specified in

electrical specification parameter 36.

The HLVD interrupt flag is not enabled until TIRVST has

expired and a stable reference voltage is reached. For

this reason, brief excursions beyond the set point may

not be detected during this interval. Refer to

Figure 23-2 or Figure 23-3.

FIGURE 23-2: LOW-VOLTAGE DETECT OPERATION (VDIRMAG = 0)

VLVD

VDD

HLVDIF

VLVD

VDD

Enable HLVD

TIRVST

HLVDIF may not be set

Enable HLVD

HLVDIF

HLVDIF cleared in software

HLVDIF cleared in software,

CASE 1:

CASE 2:

HLVDIF remains set since HLVD condition still exists

TIRVST

Internal Reference is stable

IRVST

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 23-3: HIGH-VOLTAGE DETECT OPERATION (VDIRMAG = 1)

23.5 Applications

In many applications, the ability to detect a drop below

or rise above a particular threshold is desirable. For

example, the HLVD module could be periodically

enabled to detect a Universal Serial Bus (USB) attach

or detach. This assumes the device is powered by a

lower voltage source than the USB when detached. An

attach would indicate a high-voltage detect from, for

example, 3.3V to 5V (the voltage on USB) and vice

versa for a detach. This feature could save a design a

few extra components and an attach signal (input pin).

For general battery applications, Figure 23-4 shows a

possible voltage curve. Over time, the device voltage

decreases. When the device voltage reaches voltage

VA, the HLVD logic generates an interrupt at time TA.

The interrupt could cause the execution of an ISR,

which would allow the application to perform “house-

keeping tasks” and perform a controlled shutdown

before the device voltage exits the valid operating

range at TB. The HLVD, thus, would give the applica-

tion a time window, represented by the difference

between T

A and TB, to safely exit.

FIGURE 23-4: TYPICAL LOW-VOLTAGE

DETECT APPLICATION

VLVD

VDD

HLVDIF

VLVD

VDD

Enable HLVD

TIRVST

HLVDIF may not be set

Enable HLVD

HLVDIF

HLVDIF cleared in software

HLVDIF cleared in software,

CASE 1:

CASE 2:

HLVDIF remains set since HLVD condition still exists

TIRVST

IRVST

Internal Reference is stable

IRVST

Time

Voltage

TATB

VA = HLVD trip point

VB = Minimum valid device

operating voltage

Legend:

PIC18F2221/2321/4221/4321 FAMILY

23.6 Operation During Sleep

When enabled, the HLVD circuitry continues to operate

during Sleep. If the device voltage crosses the trip

point, the HLVDIF bit will be set and the device will

wake-up from Sleep. Device execution will continue

from the interrupt vector address if interrupts have

been globally enabled.

23.7 Effects of a Reset

A device Reset forces all registers to their Reset state.

This forces the HLVD module to be turned off.

TABLE 23-1: REGISTERS ASSOCIATED WITH HIGH/LOW-VOLTAGE DETECT MODULE

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on Page

HLVDCON VDIRMAG — IRVST HLVDEN HLVDL3 HLVDL2 HLVDL1 HLVDL0 56

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 55

PIR2 OSCFIF CMIF — EEIF BCLIF HLVDIF TMR3IF CCP2IF 58

PIE2 OSCFIE CMIE —EEIE BCLIE HLVDIE TMR3IE CCP2IE 58

IPR2 OSCFIP CMIP —EEIP BCLIP HLVDIP TMR3IP CCP2IP 58

Legend: — = unimplemented, read as ‘0’. Shaded cells are unused by the HLVD module.

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

24.0 SPECIAL FEATURES OF THE

CPU

PIC18F2221/2321/4221/4321 family devices include

several features intended to maximize reliability and

minimize cost through elimination of external

components. These are:

• Oscillator Selection

• Resets:

- Power-on Reset (POR)

- Power-up Timer (PWRT)

- Oscillator Start-up Timer (OST)

- Brown-out Reset (BOR)

• Interrupts

• Watchdog Timer (WDT)

• Fail-Safe Clock Monitor

• Two-Speed Start-up

• Code Protection

• ID Locations

• In-Circuit Serial Programming

The oscillator can be configured for the application

depending on frequency, power, accuracy and cost. All

of the options are discussed in detail in Section 3.0

“Oscillator Configurations”.

A complete discussion of device Resets and interrupts

is available in previous sections of this data sheet.

In addition to their Power-up and Oscillator Start-up

Timers provided for Resets, PIC18F2221/2321/4221/

4321 family devices have a Watchdog Timer, which is

either permanently enabled via the Configuration bits

or software controlled (if configured as disabled).

The inclusion of an internal RC oscillator also provides

the additional benefits of a Fail-Safe Clock Monitor

(FSCM) and Two-Speed Start-up. FSCM provides for

background monitoring of the peripheral clock and

automatic switchover in the event of its failure. Two-

Speed Start-up enables code to be executed almost

immediately on start-up, while the primary clock source

completes its start-up delays.

All of these features are enabled and configured by

setting the appropriate Configuration register bits.

24.1 Configuration Bits

The Configuration bits can be programmed (read as

‘0’) or left unprogrammed (read as ‘1’) to select various

device configurations. These bits are mapped starting

at program memory location 300000h.

The user will note that address 300000h is beyond the

user program memory space. In fact, it belongs to the

configuration memory space (300000h-3FFFFFh), which

can only be accessed using table reads and table writes.

Programming the Configuration registers is done in a

manner similar to programming the Flash memory. The

WR bit in the EECON1 register starts a self-timed write

to the Configuration register. In normal operation mode,

a TBLWT instruction with the TBLPTR pointing to the

Configuration register sets up the address and the data

for the Configuration register write. Setting the WR bit

starts a long write to the Configuration register. The

Configuration registers are written a byte at a time. To

write or erase a configuration cell, a TBLWT instruction

can write a ‘1’ or a ‘0’ into the cell. For additional details

on Flash programming, refer to Section 7.5 “Writing

to Flash Program Memory”.

TABLE 24-1: CONFIGURATION BITS AND DEVICE IDs

File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Default/

Unprogrammed

Value

300001h CONFIG1H IESO FCMEN —— FOSC3 FOSC2 FOSC1 FOSC0 00-- 0111

300002h CONFIG2L ——— BORV1 BORV0 BOREN1 BOREN0 PWRTEN ---1 1111

300003h CONFIG2H ——— WDTPS3 WDTPS2 WDTPS1 WDTPS0 WDTEN ---1 1111

300005h CONFIG3H MCLRE — — — — LPT1OSC PBADEN CCP2MX 1--- -011

300006h CONFIG4L DEBUG XINST BBSIZ1 BBSIZ0 rLVP—STVREN1000 01-1

300008h CONFIG5L — — — — — —CP1CP0---- --11

300009h CONFIG5H CPD CPB — — — — — — 11-- ----

30000Ah CONFIG6L — — — — — —WRT1WRT0---- --11

30000Bh CONFIG6H WRTD WRTB WRTC —————111- ----

30000Ch CONFIG7L — — — — — — EBTR1 EBTR0 ---- --11

30000Dh CONFIG7H —EBTRB— — — — — — -1-- ----

3FFFFEh DEVID1(1) DEV2 DEV1 DEV0 REV4 REV3 REV2 REV1 REV0 xxxx xxxx(2)

3FFFFFh DEVID2(1) DEV10 DEV9 DEV8 DEV7 DEV6 DEV5 DEV4 DEV3 0000 1100

Legend: x = unknown, u = unchanged, - = unimplemented, q = value depends on condition, r = reserved, maintain as ‘0’.

Shaded cells are unimplemented, read as ‘0’.

Note 1: Unimplemented in PIC18F2221/4221 devices; maintain these bits set.

2: See Register 24-14 for DEVID1 values. DEVID registers are read-only and cannot be programmed by the user.

PIC18F2221/2321/4221/4321 FAMILY

R/P-0 R/P-0 U-0 U-0 R/P-0 R/P-1 R/P-1 R/P-1

IESO FCMEN —— FOSC3 FOSC2 FOSC1 FOSC0

bit 7 bit 0

bit 7 IESO: Internal/External Oscillator Switchover bit

1 = Oscillator Switchover mode enabled

0 = Oscillator Switchover mode disabled

bit 6 FCMEN: Fail-Safe Clock Monitor Enable bit

1 = Fail-Safe Clock Monitor enabled

0 = Fail-Safe Clock Monitor disabled

bit 5-4 Unimplemented: Read as ‘0’

bit 3-0 FOSC<3:0>: Oscillator Selection bits

11xx = External RC oscillator, CLKO function on RA6

101x = External RC oscillator, CLKO function on RA6

1001 = Internal oscillator block, CLKO function on RA6, port function on RA7

1000 = Internal oscillator block, port function on RA6 and RA7

0111 = External RC oscillator, port function on RA6

0110 = HS oscillator, PLL enabled (Clock Frequency = 4 x FOSC1)

0101 = EC oscillator, port function on RA6

0100 = EC oscillator, CLKO function on RA6

0011 = External RC oscillator, CLKO function on RA6

0010 = HS oscillator

0001 = XT oscillator

0000 = LP oscillator

Legend:

R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’

-n = Value when device is unprogrammed u = Unchanged from programmed state

PIC18F2221/2321/4221/4321 FAMILY

U-0 U-0 U-0 R/P-1 R/P-1 R/P-1 R/P-1 R/P-1

———BORV1

(1) BORV0(1) BOREN1(2) BOREN0(2) PWRTEN(2)

bit 7 bit 0

bit 7-5 Unimplemented: Read as ‘0’

bit 4-3 BORV<1:0>: Brown-out Reset Voltage bits(1)

11 = Minimum setting

00 = Maximum setting

bit 2-1 BOREN<1:0>: Brown-out Reset Enable bits(2)

11 = Brown-out Reset enabled in hardware only (SBOREN is disabled)

10 = Brown-out Reset enabled in hardware only and disabled in Sleep mode

(SBOREN is disabled)

01 = Brown-out Reset enabled and controlled by software (SBOREN is enabled)

00 = Brown-out Reset disabled in hardware and software

bit 0 PWRTEN: Power-up Timer Enable bit(2)

1 = PWRT disabled

0 = PWRT enabled

Note 1: See Section 27.1 “DC Characteristics” for the specifications.

2: The Power-up Timer is decoupled from Brown-out Reset, allowing these features to

be independently controlled.

Legend:

R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’

-n = Value when device is unprogrammed u = Unchanged from programmed state

PIC18F2221/2321/4221/4321 FAMILY

U-0 U-0 U-0 R/P-1 R/P-1 R/P-1 R/P-1 R/P-1

— — — WDTPS3 WDTPS2 WDTPS1 WDTPS0 WDTEN

bit 7 bit 0

bit 7-5 Unimplemented: Read as ‘0’

bit 4-1 WDTPS<3:0>: Watchdog Timer Postscale Select bits

1111 = 1:32,768

1110 = 1:16,384

1101 = 1:8,192

1100 = 1:4,096

1011 = 1:2,048

1010 = 1:1,024

1001 = 1:512

1000 = 1:256

0111 = 1:128

0110 = 1:64

0101 = 1:32

0100 = 1:16

0011 = 1:8

0010 = 1:4

0001 = 1:2

0000 = 1:1

bit 0 WDTEN: Watchdog Timer Enable bit

1 = WDT enabled

0 = WDT disabled (control is placed on the SWDTEN bit)

Legend:

R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’

-n = Value when device is unprogrammed u = Unchanged from programmed state

PIC18F2221/2321/4221/4321 FAMILY

R/P-1 U-0 U-0 U-0 U-0 R/P-0 R/P-1 R/P-1

MCLRE — — — — LPT1OSC PBADEN CCP2MX

bit 7 bit 0

bit 7 MCLRE: MCLR Pin Enable bit

1 = MCLR pin enabled; RE3 input pin disabled

0 = RE3 input pin enabled; MCLR disabled

bit 6-3 Unimplemented: Read as ‘0’

bit 2 LPT1OSC: Low-Power Timer1 Oscillator Enable bit

1 = Timer1 configured for low-power operation

0 = Timer1 configured for higher power operation

bit 1 PBADEN: PORTB A/D Enable bit

(Affects ADCON1 Reset state. ADCON1 controls PORTB<4:0> pin configuration.)

1 = PORTB<4:0> pins are configured as analog input channels on Reset

0 = PORTB<4:0> pins are configured as digital I/O on Reset

bit 0 CCP2MX: CCP2 MUX bit

1 = CCP2 input/output is multiplexed with RC1

0 = CCP2 input/output is multiplexed with RB3

Legend:

R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’

-n = Value when device is unprogrammed u = Unchanged from programmed state

PIC18F2221/2321/4221/4321 FAMILY

R/P-1 R/P-0 U-0 U-0 r-0 R/P-1 U-0 R/P-1

DEBUG XINST BBSIZ1 BBSIZ0 —LVP—STVREN

bit 7 bit 0

bit 7 DEBUG: Background Debugger Enable bit

1 = Background debugger disabled, RB6 and RB7 configured as general purpose I/O pins

0 = Background debugger enabled, RB6 and RB7 are dedicated to in-circuit debug

bit 6 XINST: Extended Instruction Set Enable bit

1 = Instruction set extension and Indexed Addressing mode enabled

0 = Instruction set extension and Indexed Addressing mode disabled (Legacy mode)

bit 5-4 BBSIZ<1:0>: Boot Block Size Select bits

PIC18F4221/4321 Devices:

1x = 1024 Words

01 = 512 Words

00 = 256 Words

PIC18F2221/2321 Devices:

1x = 512 Words

x1 = 512 Words

00 = 256 Words

bit 3 Reserved: Maintain as ‘0’

bit 2 LVP: Single-Supply ICSP™ Enable bit

1 = Single-Supply ICSP enabled

0 = Single-Supply ICSP disabled

bit 1 Unimplemented: Read as ‘0’

bit 0 STVREN: Stack Full/Underflow Reset Enable bit

1 = Stack full/underflow will cause Reset

0 = Stack full/underflow will not cause Reset

Legend: r = Reserved bit, program as ‘0’

R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’

-n = Value when device is unprogrammed u = Unchanged from programmed state

PIC18F2221/2321/4221/4321 FAMILY

U-0 U-0 U-0 U-0 U-0 U-0 R/C-1 R/C-1

——————CP1CP0

bit 7 bit 0

bit 7-2 Unimplemented: Read as ‘0’

bit 1 CP1: Code Protection bit

1 = Block 1 not code-protected(1)

0 = Block 1 code-protected(1)

bit 0 CP0: Code Protection bit

1 = Block 0 not code-protected(1)

0 = Block 0 code-protected(1)

Note 1: See Figure 24-5 for variable block boundaries.

Legend:

R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’

-n = Value when device is unprogrammed u = Unchanged from programmed state

R/C-1 R/C-1 U-0 U-0 U-0 U-0 U-0 U-0

CPD CPB — — — — — —

bit 7 bit 0

bit 7 CPD: Data EEPROM Code Protection bit

1 = Data EEPROM not code-protected

0 = Data EEPROM code-protected

bit 6 CPB: Boot Block Code Protection bit

1 = Boot block not code-protected(1)

0 = Boot block code-protected(1)

bit 5-0 Unimplemented: Read as ‘0’

Note 1: See Figure 24-5 for variable block boundaries.

Legend:

R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’

-n = Value when device is unprogrammed u = Unchanged from programmed state

PIC18F2221/2321/4221/4321 FAMILY

U-0 U-0 U-0 U-0 U-0 U-0 R/C-1 R/C-1

— — — — — — WRT1 WRT0

bit 7 bit 0

bit 7-2 Unimplemented: Read as ‘0’

bit 1 WRT1: Write Protection bit

1 = Block 1 not write-protected(1)

0 = Block 1 write-protected(1)

bit 0 WRT0: Write Protection bit

1 = Block 0 not write-protected(1)

0 = Block 0 write-protected(1)

Note 1: See Figure 24-5 for variable block boundaries.

Legend:

R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’

-n = Value when device is unprogrammed u = Unchanged from programmed state

R/C-1 R/C-1 R-1 U-0 U-0 U-0 U-0 U-0

WRTD WRTB WRTC(1) — — — — —

bit 7 bit 0

bit 7 WRTD: Data EEPROM Write Protection bit

1 = Data EEPROM not write-protected

0 = Data EEPROM write-protected

bit 6 WRTB: Boot Block Write Protection bit

1 = Boot block not write-protected(2)

0 = Boot block write-protected(2)

bit 5 WRTC: Configuration Register Write Protection bit(1)

1 = Configuration registers (300000-3000FFh) not write-protected

0 = Configuration registers (300000-3000FFh) write-protected

bit 4-0 Unimplemented: Read as ‘0’

Note 1: This bit is read-only in normal execution mode; it can be written only in Program mode.

2: See Figure 24-5 for block boundaries.

Legend:

R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’

-n = Value when device is unprogrammed u = Unchanged from programmed state

PIC18F2221/2321/4221/4321 FAMILY

U-0 U-0 U-0 U-0 U-0 U-0 R/C-1 R/C-1

— — — — — — EBTR1 EBTR0

bit 7 bit 0

bit 7-2 Unimplemented: Read as ‘0’

bit 1 EBTR1: Table Read Protection bit

1 = Block 1 not protected from table reads executed in other blocks(1)

0 = Block 1 protected from table reads executed in other blocks(1)

bit 0 EBTR0: Table Read Protection bit

1 = Block 0 not protected from table reads executed in other blocks(1)

0 = Block 0 protected from table reads executed in other blocks(1)

Note 1: See Figure 24-5 for variable block boundaries.

Legend:

R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’

-n = Value when device is unprogrammed u = Unchanged from programmed state

U-0 R/C-1 U-0 U-0 U-0 U-0 U-0 U-0

— EBTRB — — — — — —

bit 7 bit 0

bit 7 Unimplemented: Read as ‘0’

bit 6 EBTRB: Boot Block Table Read Protection bit

1 = Boot block not protected from table reads executed in other blocks(1)

0 = Boot block protected from table reads executed in other blocks(1)

bit 5-0 Unimplemented: Read as ‘0’

Note 1: See Figure 24-5 for variable block boundaries.

Legend:

R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’

-n = Value when device is unprogrammed u = Unchanged from programmed state

PIC18F2221/2321/4221/4321 FAMILY

RRRRRRRR

DEV2 DEV1 DEV0 REV4 REV3 REV2 REV1 REV0

bit 7 bit 0

bit 7-5 DEV<2:0>: Device ID bits

000 = PIC18F4321

010 = PIC18F4221

001 = PIC18F2321

011 = PIC18F2221

bit 4-0 REV<4:0>: Revision ID bits

These bits are used to indicate the device revision.

Legend:

R = Read-only bit P = Programmable bit U = Unimplemented bit, read as ‘0’

-n = Value when device is unprogrammed u = Unchanged from programmed state

RRRRRRRR

DEV10 DEV9 DEV8 DEV7 DEV6 DEV5 DEV4 DEV3

bit 7 bit 0

bit 7-0 DEV<10:3>: Device ID bits

These bits are used with the DEV<2:0> bits in the Device ID Register 1 to identify the

part number.

0010 0001 = PIC18F2221/2321/4221/4321 devices

Note: These values for DEV<10:3> may be shared with other devices. The specific

device is always identified by using the entire DEV<10:0> bit sequence.

Legend:

R = Read-only bit P = Programmable bit U = Unimplemented bit, read as ‘0’

-n = Value when device is unprogrammed u = Unchanged from programmed state

PIC18F2221/2321/4221/4321 FAMILY

24.2 Watchdog Timer (WDT)

For PIC18F2221/2321/4221/4321 family devices, the

WDT is driven by the INTRC source. When the WDT is

enabled, the clock source is also enabled. The nominal

WDT period is 4 ms and has the same stability as the

INTRC oscillator.

The 4 ms period of the WDT is multiplied by a 16-bit

postscaler. Any output of the WDT postscaler is

selected by a multiplexer, controlled by bits in Configu-

ration Register 2H. Available periods range from 4 ms

to 131.072 seconds (2.18 minutes). The WDT and

postscaler are cleared when any of the following events

occur: a SLEEP or CLRWDT instruction is executed, the

IRCF bits (OSCCON<6:4>) are changed or a clock

failure has occurred.

24.2.1 CONTROL REGISTER

readable and writable register which contains a control

bit that allows software to override the WDT enable

Configuration bit, but only if the Configuration bit has

disabled the WDT.

FIGURE 24-1: WDT BLOCK DIAGRAM

Note 1: The CLRWDT and SLEEP instructions

clear the WDT and postscaler counts

when executed.

2: Changing the setting of the IRCF bits

(OSCCON<6:4>) clears the WDT and

postscaler counts.

3: When a CLRWDT instruction is executed,

the postscaler count will be cleared.

INTRC Source

WDT

Wake-up from

Reset

WDT Counter

Programmable Postscaler

1:1 to 1:32,768

Enable WDT

WDTPS<3:0>

SWDTEN

WDTEN

CLRWDT

Power-Managed

Reset

All Device Resets

Sleep

÷128

Change on IRCF bits

Modes

PIC18F2221/2321/4221/4321 FAMILY

TABLE 24-2: SUMMARY OF WATCHDOG TIMER REGISTERS

U-0 U-0 U-0 U-0 U-0 U-0 U-0 R/W-0

— — — — — — —SWDTEN

(1)

bit 7 bit 0

bit 7-1 Unimplemented: Read as ‘0’

bit 0 SWDTEN: Software Controlled Watchdog Timer Enable bit(1)

1 = Watchdog Timer is on

0 = Watchdog Timer is off

Note 1: This bit has no effect if the Configuration bit, WDTEN, is enabled.

Legend:

R = Readable bit W = Writable bit

U = Unimplemented bit, read as ‘0’ -n = Value at POR

Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Reset

Values

on page

RCON IPEN SBOREN(1) —RI TO PD POR BOR 56

WDTCON — — — — — — —SWDTEN56

Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Watchdog Timer.

Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise, it is disabled

and reads as ‘0’. See Section 5.4 “Brown-out Reset (BOR)”.

PIC18F2221/2321/4221/4321 FAMILY

24.3 Two-Speed Start-up

The Two-Speed Start-up feature helps to minimize the

latency period from oscillator start-up to code execution

by allowing the microcontroller to use the INTOSC

oscillator as a clock source until the primary clock

source is available. It is enabled by setting the IESO

Configuration bit.

Two-Speed Start-up should be enabled only if the

primary oscillator mode is LP, XT, HS or HSPLL

(crystal-based modes). Other sources do not require

an OST start-up delay; for these, Two-Speed Start-up

should be disabled.

When enabled, Resets and wake-ups from Sleep mode

cause the device to configure itself to run from the

internal oscillator block as the clock source, following

the time-out of the Power-up Timer after a Power-on

Reset is enabled. This allows almost immediate code

execution while the primary oscillator starts and the

OST is running. Once the OST times out, the device

automatically switches to PRI_RUN mode.

To use a higher clock speed on wake-up, the INTOSC

or postscaler clock sources can be selected to provide

a higher clock speed by setting bits, IRCF<2:0>,

immediately after Reset. For wake-ups from Sleep, the

INTOSC or postscaler clock sources can be selected

by setting the IRCF<2:0> bits prior to entering Sleep

mode.

In all other power-managed modes, Two-Speed Start-

up is not used. The device will be clocked by the

currently selected clock source until the primary clock

source becomes available. The setting of the IESO bit

is ignored.

24.3.1 SPECIAL CONSIDERATIONS FOR

USING TWO-SPEED START-UP

While using the INTOSC oscillator in Two-Speed Start-

up, the device still obeys the normal command

sequences for entering power-managed modes,

including multiple SLEEP instructions (refer to

Section 4.1.4 “Multiple Sleep Commands”). In

practice, this means that user code can change the

SCS<1:0> bit settings or issue SLEEP instructions

before the OST times out. This would allow an applica-

tion to briefly wake-up, perform routine “housekeeping”

tasks and return to Sleep before the device starts to

operate from the primary oscillator.

User code can also check if the primary clock source is

currently providing the device clocking by checking the

status of the OSTS bit (OSCCON<3>). If the bit is set,

the primary oscillator is providing the clock. Otherwise,

the internal oscillator block is providing the clock during

wake-up from Reset or Sleep mode.

FIGURE 24-2: TIMING TRANSITION FOR TWO-SPEED START-UP (INTOSC TO HSPLL)

Q1 Q3 Q4

OSC1

Peripheral

Program PC PC + 2

INTOSC

PLL Clock

PC + 6

Output

Q3 Q4 Q1

CPU Clock

PC + 4

Clock

Counter

Q2 Q2 Q3

Note 1: TOST = 1024 TOSC; TPLL = 2 ms (approx). These intervals are not shown to scale.

2: Clock transition typically occurs within 2-4 TOSC.

Wake from Interrupt Event

TPLL(1)

12 n-1n

Clock

OSTS bit Set

Transition(2)

Multiplexer

TOST(1)

PIC18F2221/2321/4221/4321 FAMILY

24.4 Fail-Safe Clock Monitor

The Fail-Safe Clock Monitor (FSCM) allows the

microcontroller to continue operation in the event of an

external oscillator failure by automatically switching the

device clock to the internal oscillator block. The FSCM

function is enabled by setting the FCMEN Configuration

bit.

When FSCM is enabled, the INTRC oscillator runs at

all times to monitor clocks to peripherals and provide a

backup clock in the event of a clock failure. Clock

monitoring (shown in Figure 24-3) is accomplished by

creating a sample clock signal, which is the INTRC

output divided by 64. This allows ample time between

FSCM sample clocks for a peripheral clock edge to

occur. The peripheral device clock and the sample

clock are presented as inputs to the Clock Monitor latch

(CM). The CM is set on the falling edge of the device

clock source, but cleared on the rising edge of the

sample clock.

FIGURE 24-3: FSCM BLOCK DIAGRAM

Clock failure is tested for on the falling edge of the

sample clock. If a sample clock falling edge occurs

while CM is still set, a clock failure has been detected

(Figure 24-4). This causes the following:

• the FSCM generates an oscillator fail interrupt by

setting bit, OSCFIF (PIR2<7>);

• the device clock source is switched to the internal

oscillator block (OSCCON is not updated to show

the current clock source – this is the fail-safe

condition); and

•the WDT is reset.

During switchover, the postscaler frequency from the

internal oscillator block may not be sufficiently stable

for timing sensitive applications. In these cases, it may

be desirable to select another clock configuration and

enter an alternate power-managed mode. This can be

done to attempt a partial recovery or execute a

controlled shutdown. See Section 4.1.4 “Multiple

Sleep Commands” and Section 24.3.1 “Special

Considerations for Using Two-Speed Start-up” for

more details.

To use a higher clock speed on wake-up, the INTOSC

or postscaler clock sources can be selected to provide

a higher clock speed by setting bits, IRCF<2:0>,

immediately after Reset. For wake-ups from Sleep, the

INTOSC or postscaler clock sources can be selected

by setting the IRCF<2:0> bits prior to entering Sleep

mode.

The FSCM will detect failures of the primary or second-

ary clock sources only. If the internal oscillator block

fails, no failure would be detected, nor would any action

be possible.

24.4.1 FSCM AND THE WATCHDOG TIMER

Both the FSCM and the WDT are clocked by the

INTRC oscillator. Since the WDT operates with a

separate divider and counter, disabling the WDT has

no effect on the operation of the INTRC oscillator when

the FSCM is enabled.

As already noted, the clock source is switched to the

INTOSC clock when a clock failure is detected.

Depending on the frequency selected by the

IRCF<2:0> bits, this may mean a substantial change in

the speed of code execution. If the WDT is enabled

with a small prescale value, a decrease in clock speed

allows a WDT time-out to occur and a subsequent

device Reset. For this reason, fail-safe clock events

also reset the WDT and postscaler, allowing it to start

timing from when execution speed was changed and

decreasing the likelihood of an erroneous time-out.

24.4.2 EXITING FAIL-SAFE OPERATION

The fail-safe condition is terminated by either a device

Reset or by entering a power-managed mode. On

Reset, the controller starts the primary clock source

specified in Configuration Register 1H (with any

required start-up delays that are required for the

oscillator mode, such as OST or PLL timer). The

INTOSC multiplexer provides the device clock until the

primary clock source becomes ready (similar to a Two-

Speed Start-up). The clock source is then switched to

the primary clock (indicated by the OSTS bit in the

OSCCON register becoming set). The Fail-Safe Clock

Monitor then resumes monitoring the peripheral clock.

The primary clock source may never become ready

during start-up. In this case, operation is clocked by the

INTOSC multiplexer. The OSCCON register will remain

in its Reset state until a power-managed mode is

entered.

Peripheral

INTRC ÷ 64

(32 μs) 488 Hz

(2.048 ms)

Clock Monitor

Latch (CM)

(edge-triggered)

Clock

Failure

Detected

Source

Clock

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 24-4: FSCM TIMING DIAGRAM

24.4.3 FSCM INTERRUPTS IN

POWER-MANAGED MODES

By entering a power-managed mode, the clock

multiplexer selects the clock source selected by the

OSCCON register. Fail-Safe Monitoring of the power-

managed clock source resumes in the power-managed

mode.

If an oscillator failure occurs during power-managed

operation, the subsequent events depend on whether

or not the oscillator failure interrupt is enabled. If

enabled (OSCFIF = 1), code execution will be clocked

by the INTOSC multiplexer. An automatic transition

back to the failed clock source will not occur.

If the interrupt is disabled, subsequent interrupts while

in Idle mode will cause the CPU to begin executing

instructions while being clocked by the INTOSC

source.

24.4.4 POR OR WAKE FROM SLEEP

The FSCM is designed to detect oscillator failure at any

point after the device has exited Power-on Reset

(POR) or low-power Sleep mode. When the primary

device clock is EC, RC or INTRC modes, monitoring

can begin immediately following these events.

For oscillator modes involving a crystal or resonator

(HS, HSPLL, LP or XT), the situation is somewhat

different. Since the oscillator may require a start-up

time considerably longer than the FCSM sample clock

time, a false clock failure may be detected. To prevent

this, the internal oscillator block is automatically config-

ured as the device clock and functions until the primary

clock is stable (the OST and PLL timers have timed

out). This is identical to Two-Speed Start-up mode.

Once the primary clock is stable, the INTRC returns to

its role as the FSCM source.

As noted in Section 24.3.1 “Special Considerations

for Using Two-Speed Start-up”, it is also possible to

select another clock configuration and enter an

alternate power-managed mode while waiting for the

primary clock to become stable. When the new power-

managed mode is selected, the primary clock is

disabled.

OSCFIF

CM Output

Device

Clock

Output

Sample Clock

Failure

Detected

Oscillator

Failure

Note: The device clock is normally at a much higher frequency than the sample clock. The relative frequencies in this

example have been chosen for clarity.

(Q)

CM Test CM Test CM Test

Note: The same logic that prevents false oscilla-

tor failure interrupts on POR, or wake from

Sleep, will also prevent the detection of

the oscillator’s failure to start at all follow-

ing these events. This can be avoided by

monitoring the OSTS bit and using a

timing routine to determine if the oscillator

is taking too long to start. Even so, no

oscillator failure interrupt will be flagged.

PIC18F2221/2321/4221/4321 FAMILY

24.5 Program Verification and

Code Protection

The overall structure of the code protection on the

PIC18 Flash devices differs significantly from other

PIC® devices.

The user program memory is divided into three blocks.

One of these is a boot block of variable size. The

remainder of the memory is divided into two blocks on

binary boundaries.

Each of the three blocks has three code protection bits

associated with them. They are:

• Code-Protect bit (CPn)

• Write-Protect bit (WRTn)

• External Block Table Read bit (EBTRn)

Figure 24-5 shows the program memory organization

for 4 and 8-Kbyte devices and the specific code

protection bit associated with each block. The actual

locations of the bits are summarized in Table 24-3.

FIGURE 24-5: CODE-PROTECTED PROGRAM MEMORY FOR PIC18F2221/2321/4221/4321

FAMILY DEVICES

MEMORY SIZE/DEVICE Address

Range

Block Code Protection

Controlled By:

8Kbytes

(PIC18FX321)

4Kbytes

(PIC18FX221)

BBSIZ<1:0>

11/10 01 00 11/10/01 00

Boot Block

1K word

Boot Block

512 words

Boot Block

256 words Boot Block

512 words

Boot Block

256 words

000000h

0001FFh

CPB, WRTB, EBTRB

Block 0

1.75K words

Block 0

0.75K words

000200h

0003FFh

Block 0

1.5K words

Block 0

0.5K words

000400h

0007FFh CP0, WRT0, EBTR0

Block 0

1K word

Block 1

1K word

Block 1

1K word

000800h

000FFFh

Block 1

2K words

Block 1

2K words

Block 1

2K words Unimplemented

Reads all ‘0’s

001000h

001FFFh

CP1, WRT1, EBTR1

Unimplemented

Reads all ‘0’s

002000h

1FFFFFh

(Unimplemented Memory

Space)

PIC18F2221/2321/4221/4321 FAMILY

TABLE 24-3: SUMMARY OF CODE PROTECTION REGISTERS

24.5.1 PROGRAM MEMORY

CODE PROTECTION

The program memory may be read to or written from

any location using the table read and table write

instructions. The device ID may be read with table

reads. The Configuration registers may be read and

written with the table read and table write instructions.

In normal execution mode, the CPn bits have no direct

effect. CPn bits inhibit external reads and writes. A

block of user memory may be protected from table

writes if the WRTn Configuration bit is ‘0’. The EBTRn

bits control table reads. For a block of user memory

with the EBTRn bit set to ‘0’, a table read instruction

that executes from within that block is allowed to read.

A table read instruction that executes from a location

outside of that block is not allowed to read and will result

in reading ‘0’s. Figures 24-6 through 24-8 illustrate table

write and table read protection.

FIGURE 24-6: TABLE WRITE (WRTn) DISALLOWED

File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

300008h CONFIG5L ——————CP1CP0

300009h CONFIG5H CPD CPB — — — — — —

30000Ah CONFIG6L ——————WRT1WRT0

30000Bh CONFIG6H WRTD WRTB WRTC — — — — —

30000Ch CONFIG7L —————— EBTR1 EBTR0

30000Dh CONFIG7H — EBTRB — — — — — —

Legend: Shaded cells are unimplemented.

Note: Code protection bits may only be written to

a ‘0’ from a ‘1’ state. It is not possible to

write a ‘1’ to a bit in the ‘0’ state. Code

protection bits are only set to ‘1’ by a full

chip erase or block erase function. The full

chip erase and block erase functions can

only be initiated via ICSP operation or an

external programmer.

WRTB, EBTRB = 11

WRT0, EBTR0 = 01

WRT1, EBTR1 = 11

TBLWT*

TBLPTR = 0008FFh

PC = 003FFEh

PC = 00BFFEh

TBLWT*

Boot Block

Block 0

Block 1

Results: All table writes disabled to Blockn whenever WRTn = 0.

Note 1: See Figure 24-5 for block boundaries.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 24-7: EXTERNAL BLOCK TABLE READ (EBTRn) DISALLOWED

FIGURE 24-8: EXTERNAL BLOCK TABLE READ (EBTRn) ALLOWED

WRTB, EBTRB = 11

WRT0, EBTR0 = 10

WRT1, EBTR1 = 11

TBLRD*

TBLPTR = 0008FFh

PC = 007FFEh

Boot Block

Block 0

Block 1

Results: All table reads from external blocks to Blockn are disabled whenever EBTRn = 0.

TABLAT register returns a value of ‘0’.

Note 1: See Figure 24-5 for block boundaries.

WRTB, EBTRB = 11

WRT0, EBTR0 = 10

WRT1, EBTR1 = 11

TBLRD*

TBLPTR = 0008FFh

PC = 003FFEh

Boot Block

Block 0

Block 1

Results: Table reads permitted within Blockn, even when EBTRBn = 0.

TABLAT register returns the value of the data at the location TBLPTR.

Note 1: See Figure 24-5 for block boundaries.

PIC18F2221/2321/4221/4321 FAMILY

24.5.2 DATA EEPROM

CODE PROTECTION

The entire data EEPROM is protected from external

reads and writes by two bits: CPD and WRTD. CPD

inhibits external reads and writes of data EEPROM.

WRTD inhibits internal and external writes to data

EEPROM. The CPU can always read data EEPROM

under normal operation, regardless of the protection bit

settings.

24.5.3 CONFIGURATION REGISTER

PROTECTION

The Configuration registers can be write-protected.

The WRTC bit controls protection of the Configuration

registers. In normal execution mode, the WRTC bit is

readable only. WRTC can only be written via ICSP

operation or an external programmer.

24.6 ID Locations

Eight memory locations (200000h-200007h) are

designated as ID locations, where the user can store

checksum or other code identification numbers. These

locations are both readable and writable during normal

execution through the TBLRD and TBLWT instructions

or during program/verify. The ID locations can be read

when the device is code-protected.

24.7 In-Circuit Serial Programming

PIC18F2221/2321/4221/4321 family microcontrollers

can be serially programmed while in the end applica-

tion circuit. This is simply done with two lines for clock

and data and three other lines for power, ground and

the programming voltage. This allows customers to

manufacture boards with unprogrammed devices and

then program the microcontroller just before shipping

the product. This also allows the most recent firmware

or a custom firmware to be programmed.

24.8 In-Circuit Debugger

When the DEBUG Configuration bit is programmed to

a ‘0’, the In-Circuit Debugger functionality is enabled.

This function allows simple debugging functions when

used with MPLAB® IDE. When the microcontroller has

this feature enabled, some resources are not available

for general use. Table 24-4 shows which resources are

required by the background debugger.

TABLE 24-4: DEBUGGER RESOURCES

To use the In-Circuit Debugger function of the micro-

controller, the design must implement In-Circuit Serial

Programming connections to MCLR/VPP/RE3, VDD,

VSS, RB7 and RB6. This will interface to the In-Circuit

Debugger module available from Microchip or one of

the third party development tool companies.

24.9 Single-Supply ICSP Programming

The LVP Configuration bit enables Single-Supply ICSP

Programming (formerly known as Low-Voltage ICSP

Programming or LVP). When Single-Supply Program-

ming is enabled, the microcontroller can be programmed

without requiring high voltage being applied to the

MCLR/VPP/RE3 pin, but the RB5/KBI1/PGM pin is then

dedicated to controlling Program mode entry and is not

available as a general purpose I/O pin.

While programming, using Single-Supply Program-

ming, VDD is applied to the MCLR/VPP/RE3 pin as in

normal execution mode. To enter Programming mode,

VDD is applied to the PGM pin.

If Single-Supply ICSP Programming mode will not be

used, the LVP bit can be cleared. RB5/KBI1/PGM then

becomes available as the digital I/O pin, RB5. The LVP

bit may be set or cleared only when using standard

high-voltage programming (VIHH applied to the MCLR/

VPP/RE3 pin). Once LVP has been disabled, only the

standard high-voltage programming is available and

must be used to program the device.

Memory that is not code-protected can be erased using

either a block erase, or erased row by row, then written

at any specified VDD. If code-protected memory is to be

erased, a block erase is required. If a block erase is to

be performed when using Low-Voltage ICSP

Programming, the device must be supplied with VDD of

4.5V to 5.5V.

I/O Pins: RB6, RB7

Stack: 2 levels

Program Memory: 512 bytes

Data Memory: 10 bytes

Note 1: High-voltage programming is always

available, regardless of the state of the

LVP bit or the PGM pin, by applying VIHH

to the MCLR pin.

2: By default, Single-Supply ICSP Program-

ming is enabled in unprogrammed

devices (as supplied from Microchip) and

erased devices.

3: When Single-Supply ICSP Programming

is enabled, the RB5 pin can no longer be

used as a general purpose I/O pin.

4: When LVP is enabled, externally pull the

PGM pin to VSS to allow normal program

execution.

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

25.0 INSTRUCTION SET SUMMARY

PIC18F2221/2321/4221/4321 family devices incorpo-

rate the standard set of 75 PIC18 core instructions, as

well as an extended set of 8 new instructions for the

optimization of code that is recursive or that utilizes a

software stack. The extended set is discussed later in

this section.

25.1 Standard Instruction Set

The standard PIC18 instruction set adds many

enhancements to the previous PIC® MCU instruction

sets, while maintaining an easy migration from these

PIC MCU instruction sets. Most instructions are a

single program memory word (16 bits), but there are

four instructions that require two program memory

locations.

Each single-word instruction is a 16-bit word divided

into an opcode, which specifies the instruction type and

one or more operands, which further specify the

operation of the instruction.

The instruction set is highly orthogonal and is grouped

into four basic categories:

•Byte-oriented operations

•Bit-oriented operations

•Literal operations

•Control operations

The PIC18 instruction set summary in Table 25-2 lists

byte-oriented, bit-oriented, literal and control

operations. Table 25-1 shows the opcode field

descriptions.

Most byte-oriented instructions have three operands:

1. The file register (specified by ‘f’)

2. The destination of the result (specified by ‘d’)

3. The accessed memory (specified by ‘a’)

The file register designator ‘f’ specifies which file

designator ‘d’ specifies where the result of the

operation is to be placed. If ‘d’ is zero, the result is

placed in the WREG register. If ‘d’ is one, the result is

placed in the file register specified in the instruction.

All bit-oriented instructions have three operands:

1. The file register (specified by ‘f’)

2. The bit in the file register (specified by ‘b’)

3. The accessed memory (specified by ‘a’)

The bit field designator ‘b’ selects the number of the bit

affected by the operation, while the file register

designator ‘f’ represents the number of the file in which

the bit is located.

The literal instructions may use some of the following

operands:

• A literal value to be loaded into a file register

(specified by ‘k’)

• The desired FSR register to load the literal value

into (specified by ‘f’)

• No operand required

(specified by ‘—’)

The control instructions may use some of the following

operands:

• A program memory address (specified by ‘n’)

• The mode of the CALL or RETURN instructions

(specified by ‘s’)

• The mode of the table read and table write

instructions (specified by ‘m’)

• No operand required

(specified by ‘—’)

All instructions are a single word, except for four

double-word instructions. These instructions were

made double-word to contain the required information

in 32 bits. In the second word, the 4 MSbs are ‘1’s. If

this second word is executed as an instruction (by

itself), it will execute as a NOP.

All single-word instructions are executed in a single

instruction cycle, unless a conditional test is true or the

program counter is changed as a result of the

instruction. In these cases, the execution takes two

instruction cycles, with the additional instruction

cycle(s) executed as a NOP.

The double-word instructions execute in two instruction

cycles.

One instruction cycle consists of four oscillator periods.

Thus, for an oscillator frequency of 4 MHz, the normal

instruction execution time is 1 μs. If a conditional test is

true, or the program counter is changed as a result of

an instruction, the instruction execution time is 2 μs.

Two-word branch instructions (if true) would take 3 μs.

Figure 25-1 shows the general formats that the

instructions can have. All examples use the convention

‘nnh’ to represent a hexadecimal number.

The Instruction Set Summary, shown in Table 25-2,

lists the standard instructions recognized by the

Microchip MPASM™ Assembler.

Section 25.1.1 “Standard Instruction Set” provides

a description of each instruction.

PIC18F2221/2321/4221/4321 FAMILY

TABLE 25-1: OPCODE FIELD DESCRIPTIONS

Field Description

aRAM access bit

a = 0: RAM location in Access RAM (BSR register is ignored)

a = 1: RAM bank is specified by BSR register

bbb Bit address within an 8-bit file register (0 to 7).

BSR Bank Select Register. Used to select the current RAM bank.

C, DC, Z, OV, N ALU Status bits: Carry, Digit Carry, Zero, Overflow, Negative.

dDestination select bit

d = 0: store result in WREG

d = 1: store result in file register f

dest Destination: either the WREG register or the specified register file location.

f8-bit Register file address (00h to FFh) or 2-bit FSR designator (0h to 3h).

fs12-bit Register file address (000h to FFFh). This is the source address.

fd12-bit Register file address (000h to FFFh). This is the destination address.

GIE Global Interrupt Enable bit.

kLiteral field, constant data or label (may be either an 8-bit, 12-bit or a 20-bit value).

label Label name.

mm The mode of the TBLPTR register for the table read and table write instructions.

Only used with table read and table write instructions:

*No change to register (such as TBLPTR with table reads and writes)

*+ Post-Increment register (such as TBLPTR with table reads and writes)

*- Post-Decrement register (such as TBLPTR with table reads and writes)

+* Pre-Increment register (such as TBLPTR with table reads and writes)

nThe relative address (2’s complement number) for relative branch instructions or the direct address for

Call/Branch and Return instructions.

PC Program Counter.

PCL Program Counter Low Byte.

PCH Program Counter High Byte.

PCLATH Program Counter High Byte Latch.

PCLATU Program Counter Upper Byte Latch.

PD Power-Down bit.

PRODH Product of Multiply High Byte.

PRODL Product of Multiply Low Byte.

sFast Call/Return mode select bit

s = 0: do not update into/from shadow registers

s = 1: certain registers loaded into/from shadow registers (Fast mode)

TBLPTR 21-bit Table Pointer (points to a program memory location).

TABLAT 8-bit Table Latch.

TO Time-out bit.

TOS Top-of-Stack.

uUnused or unchanged.

WDT Watchdog Timer.

WREG Working register (accumulator).

xDon’t care (‘0’ or ‘1’). The assembler will generate code with x = 0. It is the recommended form of use for

compatibility with all Microchip software tools.

zs7-bit offset value for indirect addressing of register files (source).

zd7-bit offset value for indirect addressing of register files (destination).

{ } Optional argument.

[text] Indicates an indexed address.

(text) The contents of text.

[expr]<n> Specifies bit n of the register indicated by the pointer expr.

→Assigned to.

< > Register bit field.

∈In the set of.

italics User-defined term (font is Courier New).

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 25-1: GENERAL FORMAT FOR INSTRUCTIONS

Byte-oriented file register operations

15 10 9 8 7 0

d = 0 for result destination to be WREG register

OPCODE d a f (FILE #)

d = 1 for result destination to be file register (f)

a = 0 to force Access Bank

Bit-oriented file register operations

15 12 11 9 8 7 0

OPCODE b (BIT #) a f (FILE #)

b = 3-bit position of bit in file register (f)

Literal operations

15 8 7 0

OPCODE k (literal)

k = 8-bit immediate value

Byte to Byte move operations (2-word)

15 12 11 0

OPCODE f (Source FILE #)

CALL, GOTO and Branch operations

15 8 7 0

OPCODE n<7:0> (literal)

n = 20-bit immediate value

a = 1 for BSR to select bank

f = 8-bit file register address

a = 0 to force Access Bank

a = 1 for BSR to select bank

f = 8-bit file register address

15 12 11 0

1111 n<19:8> (literal)

15 12 11 0

1111 f (Destination FILE #)

f = 12-bit file register address

Control operations

Example Instruction

ADDWF MYREG, W, B

MOVFF MYREG1, MYREG2

BSF MYREG, bit, B

MOVLW 7Fh

GOTO Label

15 8 7 0

OPCODE n<7:0> (literal)

15 12 11 0

1111 n<19:8> (literal)

CALL MYFUNC

15 11 10 0

OPCODE n<10:0> (literal)

S = Fast bit

BRA MYFUNC

15 8 7 0

OPCODE n<7:0> (literal) BC MYFUNC

PIC18F2221/2321/4221/4321 FAMILY

TABLE 25-2: PIC18FXXXX INSTRUCTION SET

Mnemonic,

Operands Description Cycles

16-Bit Instruction Word Status

Affected Notes

MSb LSb

BYTE-ORIENTED OPERATIONS

ADDWF

ADDWFC

ANDWF

CLRF

COMF

CPFSEQ

CPFSGT

CPFSLT

DECF

DECFSZ

DCFSNZ

INCF

INCFSZ

INFSNZ

IORWF

MOVF

MOVFF

MOVWF

MULWF

NEGF

RLCF

RLNCF

RRCF

RRNCF

SETF

SUBFWB

SUBWF

SUBWFB

SWAPF

TSTFSZ

XORWF

f, d, a

f, a

f, d, a

f, a

f, d, a

fs, fd

f, a

f, d, a

f, a

f, d, a

f, a

f, d, a

Add WREG and f

Add WREG and Carry bit to f

AND WREG with f

Clear f

Complement f

Compare f with WREG, Skip =

Compare f with WREG, Skip >

Compare f with WREG, Skip <

Decrement f

Decrement f, Skip if 0

Decrement f, Skip if Not 0

Increment f

Increment f, Skip if 0

Increment f, Skip if Not 0

Inclusive OR WREG with f

Move f

Move fs (source) to 1st Word

fd (destination) 2nd Word

Move WREG to f

Multiply WREG with f

Negate f

Rotate Left f through Carry

Rotate Left f (No Carry)

Rotate Right f through Carry

Rotate Right f (No Carry)

Set f

Subtract f from WREG with

Borrow

Subtract WREG from f

Subtract WREG from f with

Borrow

Swap Nibbles in f

Test f, Skip if 0

Exclusive OR WREG with f

1 (2 or 3)

0010

0001

0110

0001

0110

0000

0010

0100

0010

0011

0100

0001

0101

1100

1111

0110

0000

0110

0011

0100

0011

0100

0110

0101

0011

0110

0001

01da0

0da

01da

101a

11da

001a

010a

000a

01da

11da

10da

11da

10da

00da

ffff

111a

001a

110a

01da

00da

100a

01da

11da

10da

011a

10da

ffff

C, DC, Z, OV, N

Z, N

None

C, DC, Z, OV, N

None

C, DC, Z, OV, N

None

Z, N

None

C, DC, Z, OV, N

C, Z, N

Z, N

C, Z, N

Z, N

None

C, DC, Z, OV, N

None

Z, N

1, 2

1,2

1, 2

1, 2, 3, 4

1, 2

1, 2, 3, 4

1, 2

Note 1: When a PORT register is modified as a function of itself (e.g., MOVF PORTB, 1, 0), the value used will be that value

present on the pins themselves. For example, if the data latch is ‘1’ for a pin configured as input and is driven low by an

external device, the data will be written back with a ‘0’.

2: If this instruction is executed on the TMR0 register (and where applicable, ‘d’ = 1), the prescaler will be cleared if

assigned.

3: If the Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The second

cycle is executed as a NOP.

4: Some instructions are two-word instructions. The second word of these instructions will be executed as a NOP unless the

first word of the instruction retrieves the information embedded in these 16 bits. This ensures that all program memory

locations have a valid instruction.

PIC18F2221/2321/4221/4321 FAMILY

BIT-ORIENTED OPERATIONS

BCF

BSF

BTFSC

BTFSS

BTG

f, b, a

f, d, a

Bit Clear f

Bit Set f

Bit Test f, Skip if Clear

Bit Test f, Skip if Set

Bit Toggle f

1 (2 or 3)

1001

1000

1011

1010

0111

bbba

ffff

None

1, 2

3, 4

1, 2

CONTROL OPERATIONS

BNC

BNN

BNOV

BNZ

BOV

BRA

CALL

CLRWDT

DAW

GOTO

NOP

POP

PUSH

RCALL

RESET

RETFIE

RETLW

RETURN

SLEEP

n, s

—

Branch if Carry

Branch if Negative

Branch if Not Carry

Branch if Not Negative

Branch if Not Overflow

Branch if Not Zero

Branch if Overflow

Branch Unconditionally

Branch if Zero

Call Subroutine 1st Word

2nd Word

Clear Watchdog Timer

Decimal Adjust WREG

Go to Address 1st Word

2nd Word

No Operation

Pop Top of Return Stack (TOS)

Push Top of Return Stack (TOS)

Relative Call

Software Device Reset

Return from Interrupt Enable

Return with Literal in WREG

Return from Subroutine

Go into Standby mode

1 (2)

1110

1101

1110

1111

0000

1110

1111

0000

1111

0000

1101

0000

0010

0110

0011

0111

0101

0001

0100

0nnn

0000

110s

kkkk

0000

1111

kkkk

0000

xxxx

0000

1nnn

0000

1100

0000

nnnn

kkkk

0000

kkkk

0000

xxxx

0000

nnnn

1111

0001

kkkk

0001

0000

nnnn

kkkk

0100

0111

kkkk

0000

xxxx

0110

0101

nnnn

1111

000s

kkkk

001s

0011

None

TO, PD

None

All

GIE/GIEH,

PEIE/GIEL

None

TO, PD

TABLE 25-2: PIC18FXXXX INSTRUCTION SET (CONTINUED)

Mnemonic,

Operands Description Cycles

16-Bit Instruction Word Status

Affected Notes

MSb LSb

Note 1: When a PORT register is modified as a function of itself (e.g., MOVF PORTB, 1, 0), the value used will be that value

present on the pins themselves. For example, if the data latch is ‘1’ for a pin configured as input and is driven low by an

external device, the data will be written back with a ‘0’.

2: If this instruction is executed on the TMR0 register (and where applicable, ‘d’ = 1), the prescaler will be cleared if

assigned.

3: If the Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The second

cycle is executed as a NOP.

4: Some instructions are two-word instructions. The second word of these instructions will be executed as a NOP unless the

first word of the instruction retrieves the information embedded in these 16 bits. This ensures that all program memory

locations have a valid instruction.

PIC18F2221/2321/4221/4321 FAMILY

LITERAL OPERATIONS

ADDLW

ANDLW

IORLW

LFSR

MOVLB

MOVLW

MULLW

RETLW

SUBLW

XORLW

f, k

Add Literal and WREG

AND Literal with WREG

Inclusive OR Literal with WREG

Move Literal (12-bit) 2nd Word

to FSR(f) 1st Word

Move Literal to BSR<3:0>

Move Literal to WREG

Multiply Literal with WREG

Return with Literal in WREG

Subtract WREG from Literal

Exclusive OR Literal with WREG

0000

1110

1111

0000

1111

1011

1001

1110

0000

0001

1110

1101

1100

1000

1010

kkkk

00ff

kkkk

0000

kkkk

C, DC, Z, OV, N

Z, N

None

C, DC, Z, OV, N

Z, N

DATA MEMORY ↔ PROGRAM MEMORY OPERATIONS

TBLRD*

TBLRD*+

TBLRD*-

TBLRD+*

TBLWT*

TBLWT*+

TBLWT*-

TBLWT+*

Table Read

Table Read with Post-Increment

Table Read with Post-Decrement

Table Read with Pre-Increment

Table Write

Table Write with Post-Increment

Table Write with Post-Decrement

Table Write with Pre-Increment

0000

1000

1001

1010

1011

1100

1101

1110

1111

None

TABLE 25-2: PIC18FXXXX INSTRUCTION SET (CONTINUED)

Mnemonic,

Operands Description Cycles

16-Bit Instruction Word Status

Affected Notes

MSb LSb

Note 1: When a PORT register is modified as a function of itself (e.g., MOVF PORTB, 1, 0), the value used will be that value

present on the pins themselves. For example, if the data latch is ‘1’ for a pin configured as input and is driven low by an

external device, the data will be written back with a ‘0’.

2: If this instruction is executed on the TMR0 register (and where applicable, ‘d’ = 1), the prescaler will be cleared if

assigned.

3: If the Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The second

cycle is executed as a NOP.

4: Some instructions are two-word instructions. The second word of these instructions will be executed as a NOP unless the

first word of the instruction retrieves the information embedded in these 16 bits. This ensures that all program memory

locations have a valid instruction.

PIC18F2221/2321/4221/4321 FAMILY

25.1.1 STANDARD INSTRUCTION SET

ADDLW ADD Literal to W

Syntax: ADDLW k

Operands: 0 ≤ k ≤ 255

Operation: (W) + k → W

Status Affected: N, OV, C, DC, Z

Encoding: 0000 1111 kkkk kkkk

Description: The contents of W are added to the

8-bit literal ‘k’ and the result is placed in

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

literal ‘k’

Process

Data

Write to W

Example: ADDLW 15h

Before Instruction

W = 10h

After Instruction

W = 25h

ADDWF ADD W to f

Syntax: ADDWF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (W) + (f) → dest

Status Affected: N, OV, C, DC, Z

Encoding: 0010 01da ffff ffff

Description: Add W to register ‘f’. If ‘d’ is ‘0’, the

result is stored in W. If ‘d’ is ‘1’, the

result is stored back in register ‘f’

(default).

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: ADDWF REG, 0, 0

Before Instruction

W = 17h

REG = 0C2h

After Instruction

W = 0D9h

REG = 0C2h

Note: All PIC18 instructions may take an optional label argument preceding the instruction mnemonic for use in

symbolic addressing. If a label is used, the instruction format then becomes: {label} instruction argument(s).

PIC18F2221/2321/4221/4321 FAMILY

ADDWFC ADD W and Carry bit to f

Syntax: ADDWFC f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (W) + (f) + (C) → dest

Status Affected: N,OV, C, DC, Z

Encoding: 0010 00da ffff ffff

Description: Add W, the Carry flag and data memory

location ‘f’. If ‘d’ is ‘0’, the result is

placed in W. If ‘d’ is ‘1’, the result is

placed in data memory location ‘f’.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: ADDWFC REG, 0, 1

Before Instruction

Carry bit = 1

REG = 02h

W=4Dh

After Instruction

Carry bit = 0

REG = 02h

W = 50h

ANDLW AND Literal with W

Syntax: ANDLW k

Operands: 0 ≤ k ≤ 255

Operation: (W) .AND. k → W

Status Affected: N, Z

Encoding: 0000 1011 kkkk kkkk

Description: The contents of W are ANDed with the

8-bit literal ‘k’. The result is placed in W.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read literal

‘k’

Process

Data

Write to W

Example: ANDLW 05Fh

Before Instruction

W=A3h

After Instruction

W = 03h

PIC18F2221/2321/4221/4321 FAMILY

ANDWF AND W with f

Syntax: ANDWF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (W) .AND. (f) → dest

Status Affected: N, Z

Encoding: 0001 01da ffff ffff

Description: The contents of W are ANDed with

in W. If ‘d’ is ‘1’, the result is stored back

in register ‘f’ (default).

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: ANDWF REG, 0, 0

Before Instruction

W = 17h

REG = C2h

After Instruction

W = 02h

REG = C2h

BC Branch if Carry

Syntax: BC n

Operands: -128 ≤ n ≤ 127

Operation: If Carry bit is ‘1’,

(PC) + 2 + 2n → PC

Status Affected: None

Encoding: 1110 0010 nnnn nnnn

Description: If the Carry bit is ‘1’, then the program

will branch.

The 2’s complement number ‘2n’ is

added to the PC. Since the PC will have

incremented to fetch the next

instruction, the new address will be

PC + 2 + 2n. This instruction is then a

two-cycle instruction.

Words: 1

Cycles: 1(2)

Q Cycle Activity:

If Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

Write to

operation

If No Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

operation

Example: HERE BC 5

Before Instruction

PC = address (HERE)

After Instruction

If Carry = 1;

PC = address (HERE + 12)

If Carry = 0;

PC = address (HERE + 2)

PIC18F2221/2321/4221/4321 FAMILY

BCF Bit Clear f

Syntax: BCF f, b {,a}

Operands: 0 ≤ f ≤ 255

0 ≤ b ≤ 7

a ∈ [0,1]

Operation: 0 → f

Status Affected: None

Encoding: 1001 bbba ffff ffff

Description: Bit ‘b’ in register ‘f’ is cleared.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write

Example: BCF FLAG_REG, 7, 0

Before Instruction

FLAG_REG = C7h

After Instruction

FLAG_REG = 47h

BN Branch if Negative

Syntax: BN n

Operands: -128 ≤ n ≤ 127

Operation: If Negative bit is ‘1’,

(PC) + 2 + 2n → PC

Status Affected: None

Encoding: 1110 0110 nnnn nnnn

Description: If the Negative bit is ‘1’, then the

program will branch.

The 2’s complement number ‘2n’ is

added to the PC. Since the PC will have

incremented to fetch the next

instruction, the new address will be

PC + 2 + 2n. This instruction is then a

two-cycle instruction.

Words: 1

Cycles: 1(2)

Q Cycle Activity:

If Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

Write to

operation

If No Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

operation

Example: HERE BN Jump

Before Instruction

PC = address (HERE)

After Instruction

If Negative = 1;

PC = address (Jump)

If Negative = 0;

PC = address (HERE + 2)

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BNC Branch if Not Carry

Syntax: BNC n

Operands: -128 ≤ n ≤ 127

Operation: If Carry bit is ‘0’,

(PC) + 2 + 2n → PC

Status Affected: None

Encoding: 1110 0011 nnnn nnnn

Description: If the Carry bit is ‘0’, then the program

will branch.

The 2’s complement number ‘2n’ is

added to the PC. Since the PC will have

incremented to fetch the next

instruction, the new address will be

PC + 2 + 2n. This instruction is then a

two-cycle instruction.

Words: 1

Cycles: 1(2)

Q Cycle Activity:

If Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

Write to

operation

If No Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

operation

Example: HERE BNC Jump

Before Instruction

PC = address (HERE)

After Instruction

If Carry = 0;

PC = address (Jump)

If Carry = 1;

PC = address (HERE + 2)

BNN Branch if Not Negative

Syntax: BNN n

Operands: -128 ≤ n ≤ 127

Operation: If Negative bit is ‘0’,

(PC) + 2 + 2n → PC

Status Affected: None

Encoding: 1110 0111 nnnn nnnn

Description: If the Negative bit is ‘0’, then the

program will branch.

The 2’s complement number ‘2n’ is

added to the PC. Since the PC will have

incremented to fetch the next

instruction, the new address will be

PC + 2 + 2n. This instruction is then a

two-cycle instruction.

Words: 1

Cycles: 1(2)

Q Cycle Activity:

If Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

Write to

operation

If No Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

operation

Example: HERE BNN Jump

Before Instruction

PC = address (HERE)

After Instruction

If Negative = 0;

PC = address (Jump)

If Negative = 1;

PC = address (HERE + 2)

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BNOV Branch if Not Overflow

Syntax: BNOV n

Operands: -128 ≤ n ≤ 127

Operation: If Overflow bit is ‘0’,

(PC) + 2 + 2n → PC

Status Affected: None

Encoding: 1110 0101 nnnn nnnn

Description: If the Overflow bit is ‘0’, then the

program will branch.

The 2’s complement number ‘2n’ is

added to the PC. Since the PC will have

incremented to fetch the next

instruction, the new address will be

PC + 2 + 2n. This instruction is then a

two-cycle instruction.

Words: 1

Cycles: 1(2)

Q Cycle Activity:

If Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

Write to

operation

If No Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

operation

Example: HERE BNOV Jump

Before Instruction

PC = address (HERE)

After Instruction

If Overflow = 0;

PC = address (Jump)

If Overflow = 1;

PC = address (HERE + 2)

BNZ Branch if Not Zero

Syntax: BNZ n

Operands: -128 ≤ n ≤ 127

Operation: If Zero bit is ‘0’,

(PC) + 2 + 2n → PC

Status Affected: None

Encoding: 1110 0001 nnnn nnnn

Description: If the Zero bit is ‘0’, then the program

will branch.

The 2’s complement number ‘2n’ is

added to the PC. Since the PC will have

incremented to fetch the next

instruction, the new address will be

PC + 2 + 2n. This instruction is then a

two-cycle instruction.

Words: 1

Cycles: 1(2)

Q Cycle Activity:

If Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

Write to

operation

If No Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

operation

Example: HERE BNZ Jump

Before Instruction

PC = address (HERE)

After Instruction

If Zero = 0;

PC = address (Jump)

If Zero = 1;

PC = address (HERE + 2)

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BRA Unconditional Branch

Syntax: BRA n

Operands: -1024 ≤ n ≤ 1023

Operation: (PC) + 2 + 2n → PC

Status Affected: None

Encoding: 1101 0nnn nnnn nnnn

Description: Add the 2’s complement number ‘2n’ to

the PC. Since the PC will have

incremented to fetch the next instruction,

the new address will be PC + 2 + 2n. This

instruction is a two-cycle instruction.

Words: 1

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

Write to

operation

Example: HERE BRA Jump

Before Instruction

PC = address (HERE)

After Instruction

PC = address (Jump)

BSF Bit Set f

Syntax: BSF f, b {,a}

Operands: 0 ≤ f ≤ 255

0 ≤ b ≤ 7

a ∈ [0,1]

Operation: 1 → f

Status Affected: None

Encoding: 1000 bbba ffff ffff

Description: Bit ‘b’ in register ‘f’ is set.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write

Example: BSF FLAG_REG, 7, 1

Before Instruction

FLAG_REG = 0Ah

After Instruction

FLAG_REG = 8Ah

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BTFSC Bit Test File, Skip if Clear

Syntax: BTFSC f, b {,a}

Operands: 0 ≤ f ≤ 255

0 ≤ b ≤ 7

a ∈ [0,1]

Operation: skip if (f) = 0

Status Affected: None

Encoding: 1011 bbba ffff ffff

Description: If bit ‘b’ in register ‘f’ is ‘0’, then the next

instruction is skipped. If bit ‘b’ is ‘0’, then

the next instruction fetched during the

current instruction execution is discarded

and a NOP is executed instead, making

this a two-cycle instruction.

If ‘a’ is ‘0’, the Access Bank is selected. If

‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates in

Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh).

See Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1(2)

Note: 3 cycles if skip and followed

by a 2-word instruction.

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

operation

If skip:

Q1 Q2 Q3 Q4

operation

If skip and followed by 2-word instruction:

Q1 Q2 Q3 Q4

operation

Example: HERE

FALSE

TRUE

BTFSC

FLAG, 1, 0

Before Instruction

PC = address (HERE)

After Instruction

If FLAG<1> = 0;

PC = address (TRUE)

If FLAG<1> = 1;

PC = address (FALSE)

BTFSS Bit Test File, Skip if Set

Syntax: BTFSS f, b {,a}

Operands: 0 ≤ f ≤ 255

0 ≤ b < 7

a ∈ [0,1]

Operation: skip if (f) = 1

Status Affected: None

Encoding: 1010 bbba ffff ffff

Description: If bit ‘b’ in register ‘f’ is ‘1’, then the next

instruction is skipped. If bit ‘b’ is ‘1’, then

the next instruction fetched during the

current instruction execution is discarded

and a NOP is executed instead, making

this a two-cycle instruction.

If ‘a’ is ‘0’, the Access Bank is selected. If

‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh).

See Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1(2)

Note: 3 cycles if skip and followed

by a 2-word instruction.

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

operation

If skip:

Q1 Q2 Q3 Q4

operation

If skip and followed by 2-word instruction:

Q1 Q2 Q3 Q4

operation

Example: HERE

FALSE

TRUE

BTFSS

FLAG, 1, 0

Before Instruction

PC = address (HERE)

After Instruction

If FLAG<1> = 0;

PC = address (FALSE)

If FLAG<1> = 1;

PC = address (TRUE)

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BTG Bit Toggle f

Syntax: BTG f, b {,a}

Operands: 0 ≤ f ≤ 255

0 ≤ b < 7

a ∈ [0,1]

Operation: (f) → f

Status Affected: None

Encoding: 0111 bbba ffff ffff

Description: Bit ‘b’ in data memory location ‘f’ is

inverted.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write

Example: BTG PORTC, 4, 0

Before Instruction:

PORTC = 0111 0101 [75h]

After Instruction:

PORTC = 0110 0101 [65h]

BOV Branch if Overflow

Syntax: BOV n

Operands: -128 ≤ n ≤ 127

Operation: If Overflow bit is ‘1’,

(PC) + 2 + 2n → PC

Status Affected: None

Encoding: 1110 0100 nnnn nnnn

Description: If the Overflow bit is ‘1’, then the

program will branch.

The 2’s complement number ‘2n’ is

added to the PC. Since the PC will have

incremented to fetch the next

instruction, the new address will be

PC + 2 + 2n. This instruction is then a

two-cycle instruction.

Words: 1

Cycles: 1(2)

Q Cycle Activity:

If Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

Write to

operation

If No Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

operation

Example: HERE BOV Jump

Before Instruction

PC = address (HERE)

After Instruction

If Overflow = 1;

PC = address (Jump)

If Overflow = 0;

PC = address (HERE + 2)

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BZ Branch if Zero

Syntax: BZ n

Operands: -128 ≤ n ≤ 127

Operation: If Zero bit is ‘1’,

(PC) + 2 + 2n → PC

Status Affected: None

Encoding: 1110 0000 nnnn nnnn

Description: If the Zero bit is ‘1’, then the program

will branch.

The 2’s complement number ‘2n’ is

added to the PC. Since the PC will

have incremented to fetch the next

instruction, the new address will be

PC + 2 + 2n. This instruction is then a

two-cycle instruction.

Words: 1

Cycles: 1(2)

Q Cycle Activity:

If Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

Write to

operation

If No Jump:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

Process

Data

operation

Example: HERE BZ Jump

Before Instruction

PC = address (HERE)

After Instruction

If Zero = 1;

PC = address (Jump)

If Zero = 0;

PC = address (HERE + 2)

CALL Subroutine Call

Syntax: CALL k {,s}

Operands: 0 ≤ k ≤ 1048575

s ∈ [0,1]

Operation: (PC) + 4 → TOS,

k → PC<20:1>;

if s = 1,

(W) → WS,

(STATUS) → STATUSS,

(BSR) → BSRS

Status Affected: None

Encoding:

1st word (k<7:0>)

2nd word(k<19:8>)

1110

1111

110s

k19kkk

k7kkk

kkkk

kkkk0

kkkk8

Description: Subroutine call of entire 2-Mbyte

memory range. First, return address

(PC + 4) is pushed onto the return

stack. If ‘s’ = 1, the W, STATUS and

BSR registers are also pushed into their

respective shadow registers, WS,

STATUSS and BSRS. If ‘s’ = 0, no

update occurs (default). Then, the

20-bit value ‘k’ is loaded into PC<20:1>.

CALL is a two-cycle instruction.

Words: 2

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read literal

‘k’<7:0>,

PUSH PC to

stack

Read literal

‘k’<19:8>,

Write to PC

operation

Example: HERE CALL THERE, 1

Before Instruction

PC = address (HERE)

After Instruction

PC = address (THERE)

TOS = address (HERE + 4)

WS = W

BSRS = BSR

STATUSS = STATUS

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CLRF Clear f

Syntax: CLRF f {,a}

Operands: 0 ≤ f ≤ 255

a ∈ [0,1]

Operation: 000h → f,

1 → Z

Status Affected: Z

Encoding: 0110 101a ffff ffff

Description: Clears the contents of the specified

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write

Example: CLRF FLAG_REG, 1

Before Instruction

FLAG_REG = 5Ah

After Instruction

FLAG_REG = 00h

CLRWDT Clear Watchdog Timer

Syntax: CLRWDT

Operands: None

Operation: 000h → WDT,

000h → WDT postscaler,

1 → TO,

1 → PD

Status Affected: TO, PD

Encoding: 0000 0000 0000 0100

Description: CLRWDT instruction resets the

Watchdog Timer. It also resets the

postscaler of the WDT. Status bits, TO

and PD, are set.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode No

operation

Process

Data

operation

Example: CLRWDT

Before Instruction

WDT Counter = ?

After Instruction

WDT Counter = 00h

WDT Postscaler = 0

TO =1

PD =1

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COMF Complement f

Syntax: COMF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f) → dest

Status Affected: N, Z

Encoding: 0001 11da ffff ffff

Description: The contents of register ‘f’ are

complemented. If ‘d’ is ‘0’, the result is

stored in W. If ‘d’ is ‘1’, the result is

stored back in register ‘f’ (default).

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: COMF REG, 0, 0

Before Instruction

REG = 13h

After Instruction

REG = 13h

W=ECh

CPFSEQ Compare f with W, Skip if f = W

Syntax: CPFSEQ f {,a}

Operands: 0 ≤ f ≤ 255

a ∈ [0,1]

Operation: (f) – (W),

skip if (f) = (W)

(unsigned comparison)

Status Affected: None

Encoding: 0110 001a ffff ffff

Description: Compares the contents of data memory

location ‘f’ to the contents of W by

performing an unsigned subtraction.

If ‘f’ = W, then the fetched instruction is

discarded and a NOP is executed

instead, making this a two-cycle

instruction.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1(2)

Note: 3 cycles if skip and followed

by a 2-word instruction.

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

operation

If skip:

Q1 Q2 Q3 Q4

operation

If skip and followed by 2-word instruction:

Q1 Q2 Q3 Q4

operation

Example: HERE CPFSEQ REG, 0

NEQUAL :

EQUAL :

Before Instruction

PC Address = HERE

W=?

REG = ?

After Instruction

If REG = W;

PC = Address (EQUAL)

If REG ≠ W;

PC = Address (NEQUAL)

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CPFSGT Compare f with W, Skip if f > W

Syntax: CPFSGT f {,a}

Operands: 0 ≤ f ≤ 255

a ∈ [0,1]

Operation: (f) – (W),

skip if (f) > (W)

(unsigned comparison)

Status Affected: None

Encoding: 0110 010a ffff ffff

Description: Compares the contents of data memory

location ‘f’ to the contents of the W by

performing an unsigned subtraction.

If the contents of ‘f’ are greater than the

contents of WREG, then the fetched

instruction is discarded and a NOP is

executed instead, making this a

two-cycle instruction.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1(2)

Note: 3 cycles if skip and followed

by a 2-word instruction.

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

operation

If skip:

Q1 Q2 Q3 Q4

operation

If skip and followed by 2-word instruction:

Q1 Q2 Q3 Q4

operation

Example: HERE CPFSGT REG, 0

NGREATER :

GREATER :

Before Instruction

PC = Address (HERE)

W= ?

After Instruction

If REG > W;

PC = Address (GREATER)

If REG ≤ W;

PC = Address (NGREATER)

CPFSLT Compare f with W, Skip if f < W

Syntax: CPFSLT f {,a}

Operands: 0 ≤ f ≤ 255

a ∈ [0,1]

Operation: (f) – (W),

skip if (f) < (W)

(unsigned comparison)

Status Affected: None

Encoding: 0110 000a ffff ffff

Description: Compares the contents of data memory

location ‘f’ to the contents of W by

performing an unsigned subtraction.

If the contents of ‘f’ are less than the

contents of W, then the fetched

instruction is discarded and a NOP is

executed instead, making this a

two-cycle instruction.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

Words: 1

Cycles: 1(2)

Note: 3 cycles if skip and followed

by a 2-word instruction.

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

operation

If skip:

Q1 Q2 Q3 Q4

operation

If skip and followed by 2-word instruction:

Q1 Q2 Q3 Q4

operation

Example: HERE CPFSLT REG, 1

NLESS :

LESS :

Before Instruction

PC = Address (HERE)

W= ?

After Instruction

If REG < W;

PC = Address (LESS)

If REG ≥ W;

PC = Address (NLESS)

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DAW Decimal Adjust W Register

Syntax: DAW

Operands: None

Operation: If [W<3:0> > 9] or [DC = 1] then,

(W<3:0>) + 6 → W<3:0>;

else,

(W<3:0>) → W<3:0>

If [W<7:4> + DC > 9] or [C = 1] then,

(W<7:4>) + 6 + DC → W<7:4>;

else,

(W<7:4>) + DC → W<7:4>

Status Affected: C

Encoding: 0000 0000 0000 0111

Description: DAW adjusts the eight-bit value in W

resulting from the earlier addition of two

variables (each in packed BCD format)

and produces a correct packed BCD

result.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write

Example 1:

DAW

Before Instruction

W=A5h

C=0

DC = 0

After Instruction

W = 05h

C=1

DC = 0

Example 2:

Before Instruction

W=CEh

C=0

DC = 0

After Instruction

W = 34h

C=1

DC = 0

DECF Decrement f

Syntax: DECF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f) – 1 → dest

Status Affected: C, DC, N, OV, Z

Encoding: 0000 01da ffff ffff

Description: Decrement register ‘f’. If ‘d’ is ‘0’, the

result is stored in W. If ‘d’ is ‘1’, the

result is stored back in register ‘f’

(default).

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: DECF CNT, 1, 0

Before Instruction

CNT = 01h

Z=0

After Instruction

CNT = 00h

Z=1

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DECFSZ Decrement f, Skip if 0

Syntax: DECFSZ f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f) – 1 → dest,

skip if result = 0

Status Affected: None

Encoding: 0010 11da ffff ffff

Description: The contents of register ‘f’ are

decremented. If ‘d’ is ‘0’, the result is

placed in W. If ‘d’ is ‘1’, the result is

placed back in register ‘f’ (default).

If the result is ‘0’, the next instruction,

which is already fetched, is discarded

and a NOP is executed instead, making

it a two-cycle instruction.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1(2)

Note: 3 cycles if skip and followed

by a 2-word instruction.

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

If skip:

Q1 Q2 Q3 Q4

operation

If skip and followed by 2-word instruction:

Q1 Q2 Q3 Q4

operation

Example: HERE DECFSZ CNT, 1, 1

GOTO LOOP

CONTINUE

Before Instruction

PC = Address (HERE)

After Instruction

CNT = CNT – 1

If CNT = 0;

PC = Address (CONTINUE)

If CNT ≠0;

PC = Address (HERE + 2)

DCFSNZ Decrement f, Skip if Not 0

Syntax: DCFSNZ f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f) – 1 → dest,

skip if result ≠ 0

Status Affected: None

Encoding: 0100 11da ffff ffff

Description: The contents of register ‘f’ are

decremented. If ‘d’ is ‘0’, the result is

placed in W. If ‘d’ is ‘1’, the result is

placed back in register ‘f’ (default).

If the result is not ‘0’, the next

instruction, which is already fetched, is

discarded and a NOP is executed

instead, making it a two-cycle

instruction.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1(2)

Note: 3 cycles if skip and followed

by a 2-word instruction.

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

If skip:

Q1 Q2 Q3 Q4

operation

If skip and followed by 2-word instruction:

Q1 Q2 Q3 Q4

operation

Example: HERE DCFSNZ TEMP, 1, 0

ZERO :

NZERO :

Before Instruction

TEMP = ?

After Instruction

TEMP = TEMP – 1

If TEMP = 0;

PC = Address (ZERO)

If TEMP ≠0;

PC = Address (NZERO)

PIC18F2221/2321/4221/4321 FAMILY

GOTO Unconditional Branch

Syntax: GOTO k

Operands: 0 ≤ k ≤ 1048575

Operation: k → PC<20:1>

Status Affected: None

Encoding:

1st word (k<7:0>)

2nd word(k<19:8>)

1110

1111

k19kkk

k7kkk

kkkk

kkkk0

kkkk8

Description: GOTO allows an unconditional branch

anywhere within entire

2-Mbyte memory range. The 20-bit

value ‘k’ is loaded into PC<20:1>.

GOTO is always a two-cycle

instruction.

Words: 2

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read literal

‘k’<7:0>,

operation

Read literal

‘k’<19:8>,

Write to PC

operation

Example: GOTO THERE

After Instruction

PC = Address (THERE)

INCF Increment f

Syntax: INCF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f) + 1 → dest

Status Affected: C, DC, N, OV, Z

Encoding: 0010 10da ffff ffff

Description: The contents of register ‘f’ are

incremented. If ‘d’ is ‘0’, the result is

placed in W. If ‘d’ is ‘1’, the result is

placed back in register ‘f’ (default).

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: INCF CNT, 1, 0

Before Instruction

CNT = FFh

Z=0

C=?

DC = ?

After Instruction

CNT = 00h

Z=1

C=1

DC = 1

PIC18F2221/2321/4221/4321 FAMILY

INCFSZ Increment f, Skip if 0

Syntax: INCFSZ f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f) + 1 → dest,

skip if result = 0

Status Affected: None

Encoding: 0011 11da ffff ffff

Description: The contents of register ‘f’ are

incremented. If ‘d’ is ‘0’, the result is

placed in W. If ‘d’ is ‘1’, the result is

placed back in register ‘f’ (default).

If the result is ‘0’, the next instruction,

which is already fetched, is discarded

and a NOP is executed instead, making

it a two-cycle instruction.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1(2)

Note: 3 cycles if skip and followed

by a 2-word instruction.

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

If skip:

Q1 Q2 Q3 Q4

operation

If skip and followed by 2-word instruction:

Q1 Q2 Q3 Q4

operation

Example: HERE INCFSZ CNT, 1, 0

NZERO :

ZERO :

Before Instruction

PC = Address (HERE)

After Instruction

CNT = CNT + 1

If CNT = 0;

PC = Address (ZERO)

If CNT ≠0;

PC = Address (NZERO)

INFSNZ Increment f, Skip if Not 0

Syntax: INFSNZ f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f) + 1 → dest,

skip if result ≠ 0

Status Affected: None

Encoding: 0100 10da ffff ffff

Description: The contents of register ‘f’ are

incremented. If ‘d’ is ‘0’, the result is

placed in W. If ‘d’ is ‘1’, the result is

placed back in register ‘f’ (default).

If the result is not ‘0’, the next

instruction, which is already fetched, is

discarded and a NOP is executed

instead, making it a two-cycle

instruction.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1(2)

Note: 3 cycles if skip and followed

by a 2-word instruction.

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

If skip:

Q1 Q2 Q3 Q4

operation

If skip and followed by 2-word instruction:

Q1 Q2 Q3 Q4

operation

Example: HERE INFSNZ REG, 1, 0

ZERO

NZERO

Before Instruction

PC = Address (HERE)

After Instruction

REG = REG + 1

If REG ≠0;

PC = Address (NZERO)

If REG = 0;

PC = Address (ZERO)

PIC18F2221/2321/4221/4321 FAMILY

IORLW Inclusive OR Literal with W

Syntax: IORLW k

Operands: 0 ≤ k ≤ 255

Operation: (W) .OR. k → W

Status Affected: N, Z

Encoding: 0000 1001 kkkk kkkk

Description: The contents of W are ORed with the

eight-bit literal ‘k’. The result is placed in

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

literal ‘k’

Process

Data

Write to W

Example: IORLW 35h

Before Instruction

W=9Ah

After Instruction

W=BFh

IORWF Inclusive OR W with f

Syntax: IORWF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (W) .OR. (f) → dest

Status Affected: N, Z

Encoding: 0001 00da ffff ffff

Description: Inclusive OR W with register ‘f’. If ‘d’ is

‘0’, the result is placed in W. If ‘d’ is ‘1’,

the result is placed back in register ‘f’

(default).

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: IORWF RESULT, 0, 1

Before Instruction

RESULT = 13h

W = 91h

After Instruction

RESULT = 13h

W = 93h

PIC18F2221/2321/4221/4321 FAMILY

LFSR Load FSR

Syntax: LFSR f, k

Operands: 0 ≤ f ≤ 2

0 ≤ k ≤ 4095

Operation: k → FSRf

Status Affected: None

Encoding: 1110

1111

1110

0000

00ff

k7kkk

k11kkk

kkkk

Description: The 12-bit literal ‘k’ is loaded into the

File Select Register pointed to by ‘f’.

Words: 2

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read literal

‘k’ MSB

Process

Data

Write

literal ‘k’

MSB to

FSRfH

Decode Read literal

‘k’ LSB

Process

Data

Write literal

‘k’ to FSRfL

Example: LFSR 2, 3ABh

After Instruction

FSR2H = 03h

FSR2L = ABh

MOVF Move f

Syntax: MOVF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: f → dest

Status Affected: N, Z

Encoding: 0101 00da ffff ffff

Description: The contents of register ‘f’ are moved to

a destination dependent upon the

status of ‘d’. If ‘d’ is ‘0’, the result is

placed in W. If ‘d’ is ‘1’, the result is

placed back in register ‘f’ (default).

Location ‘f’ can be anywhere in the

256-byte bank.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write W

Example: MOVF REG, 0, 0

Before Instruction

REG = 22h

W=FFh

After Instruction

REG = 22h

W = 22h

PIC18F2221/2321/4221/4321 FAMILY

MOVFF Move f to f

Syntax: MOVFF fs,fd

Operands: 0 ≤ fs ≤ 4095

0 ≤ fd ≤ 4095

Operation: (fs) → fd

Status Affected: None

Encoding:

1st word (source)

2nd word (destin.)

1100

1111

ffff

ffffs

ffffd

Description: The contents of source register ‘fs’ are

moved to destination register ‘fd’.

Location of source ‘fs’ can be anywhere

in the 4096-byte data space (000h to

FFFh) and location of destination ‘fd’

can also be anywhere from 000h to

FFFh.

Either source or destination can be W

(a useful special situation).

MOVFF is particularly useful for

transferring a data memory location to a

peripheral register (such as the transmit

buffer or an I/O port).

The MOVFF instruction cannot use the

PCL, TOSU, TOSH or TOSL as the

destination register.

Words: 2

Cycles: 2 (3)

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

(src)

Process

Data

operation

Decode No

operation

No dummy

read

operation

Write

(dest)

Example: MOVFF REG1, REG2

Before Instruction

REG1 = 33h

REG2 = 11h

After Instruction

REG1 = 33h

REG2 = 33h

MOVLB Move Literal to Low Nibble in BSR

Syntax: MOVLW k

Operands: 0 ≤ k ≤ 255

Operation: k → BSR

Status Affected: None

Encoding: 0000 0001 kkkk kkkk

Description: The eight-bit literal ‘k’ is loaded into the

Bank Select Register (BSR). The value of

BSR<7:4> always remains ‘0’, regardless

of the value of k7:k4.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

literal ‘k’

Process

Data

Write literal

‘k’ to BSR

Example: MOVLB 5

Before Instruction

BSR Register = 02h

After Instruction

BSR Register = 05h

PIC18F2221/2321/4221/4321 FAMILY

MOVLW Move Literal to W

Syntax: MOVLW k

Operands: 0 ≤ k ≤ 255

Operation: k → W

Status Affected: None

Encoding: 0000 1110 kkkk kkkk

Description: The eight-bit literal ‘k’ is loaded into W.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

literal ‘k’

Process

Data

Write to W

Example: MOVLW 5Ah

After Instruction

W=5Ah

MOVWF Move W to f

Syntax: MOVWF f {,a}

Operands: 0 ≤ f ≤ 255

a ∈ [0,1]

Operation: (W) → f

Status Affected: None

Encoding: 0110 111a ffff ffff

Description: Move data from W to register ‘f’.

Location ‘f’ can be anywhere in the

256-byte bank.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write

Example: MOVWF REG, 0

Before Instruction

W=4Fh

REG = FFh

After Instruction

W=4Fh

REG = 4Fh

PIC18F2221/2321/4221/4321 FAMILY

MULLW Multiply Literal with W

Syntax: MULLW k

Operands: 0 ≤ k ≤ 255

Operation: (W) x k → PRODH:PRODL

Status Affected: None

Encoding: 0000 1101 kkkk kkkk

Description: An unsigned multiplication is carried

out between the contents of W and the

8-bit literal ‘k’. The 16-bit result is

placed in the PRODH:PRODL register

pair. PRODH contains the high byte.

W is unchanged.

None of the Status flags are affected.

Note that neither Overflow nor Carry is

possible in this operation. A Zero result

is possible but not detected.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

literal ‘k’

Process

Data

Write

registers

PRODH:

PRODL

Example: MULLW 0C4h

Before Instruction

W=E2h

PRODH = ?

PRODL = ?

After Instruction

W=E2h

PRODH = ADh

PRODL = 08h

MULWF Multiply W with f

Syntax: MULWF f {,a}

Operands: 0 ≤ f ≤ 255

a ∈ [0,1]

Operation: (W) x (f) → PRODH:PRODL

Status Affected: None

Encoding: 0000 001a ffff ffff

Description: An unsigned multiplication is carried

out between the contents of W and the

result is stored in the PRODH:PRODL

high byte. Both W and ‘f’ are

unchanged.

None of the Status flags are affected.

Note that neither Overflow nor Carry is

possible in this operation. A Zero

result is possible but not detected.

If ‘a’ is ‘0’, the Access Bank is

selected. If ‘a’ is ‘1’, the BSR is used

to select the GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction

operates in Indexed Literal Offset

Addressing mode whenever

f ≤ 95 (5Fh). See Section 25.2.3

“Byte-Oriented and Bit-Oriented

Instructions in Indexed Literal Offset

Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write

registers

PRODH:

PRODL

Example: MULWF REG, 1

Before Instruction

W=C4h

REG = B5h

PRODH = ?

PRODL = ?

After Instruction

W=C4h

REG = B5h

PRODH = 8Ah

PRODL = 94h

PIC18F2221/2321/4221/4321 FAMILY

NEGF Negate f

Syntax: NEGF f {,a}

Operands: 0 ≤ f ≤ 255

a ∈ [0,1]

Operation: (f) + 1 → f

Status Affected: N, OV, C, DC, Z

Encoding: 0110 110a ffff ffff

Description: Location ‘f’ is negated using two’s

complement. The result is placed in the

data memory location ‘f’.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write

Example: NEGF REG, 1

Before Instruction

REG = 0011 1010 [3Ah]

After Instruction

REG = 1100 0110 [C6h]

NOP No Operation

Syntax: NOP

Operands: None

Operation: No operation

Status Affected: None

Encoding: 0000

1111

0000

xxxx

0000

xxxx

0000

xxxx

Description: No operation.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode No

operation

Example:

None.

PIC18F2221/2321/4221/4321 FAMILY

POP Pop Top of Return Stack

Syntax: POP

Operands: None

Operation: (TOS) → bit bucket

Status Affected: None

Encoding: 0000 0000 0000 0110

Description: The TOS value is pulled off the return

stack and is discarded. The TOS value

then becomes the previous value that

was pushed onto the return stack.

This instruction is provided to enable

the user to properly manage the return

stack to incorporate a software stack.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode No

operation

POP TOS

value

operation

Example: POP

GOTO NEW

Before Instruction

TOS = 0031A2h

Stack (1 level down) = 014332h

After Instruction

TOS = 014332h

PC = NEW

PUSH Push Top of Return Stack

Syntax: PUSH

Operands: None

Operation: (PC + 2) → TOS

Status Affected: None

Encoding: 0000 0000 0000 0101

Description: The PC + 2 is pushed onto the top of

the return stack. The previous TOS

value is pushed down on the stack.

This instruction allows implementing a

software stack by modifying TOS and

then pushing it onto the return stack.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode PUSH

PC + 2 onto

return stack

operation

Example: PUSH

Before Instruction

TOS = 345Ah

PC = 0124h

After Instruction

PC = 0126h

TOS = 0126h

Stack (1 level down) = 345Ah

PIC18F2221/2321/4221/4321 FAMILY

RCALL Relative Call

Syntax: RCALL n

Operands: -1024 ≤ n ≤ 1023

Operation: (PC) + 2 → TOS,

(PC) + 2 + 2n → PC

Status Affected: None

Encoding: 1101 1nnn nnnn nnnn

Description: Subroutine call with a jump up to 1K

from the current location. First, return

address (PC + 2) is pushed onto the

stack. Then, add the 2’s complement

number ‘2n’ to the PC. Since the PC will

have incremented to fetch the next

instruction, the new address will be

PC + 2 + 2n. This instruction is a

two-cycle instruction.

Words: 1

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read literal

‘n’

PUSH PC

to stack

Process

Data

Write to

operation

Example: HERE RCALL Jump

Before Instruction

PC = Address (HERE)

After Instruction

PC = Address (Jump)

TOS = Address (HERE + 2)

RESET Reset

Syntax: RESET

Operands: None

Operation: Reset all registers and flags that are

affected by a MCLR Reset.

Status Affected: All

Encoding: 0000 0000 1111 1111

Description: This instruction provides a way to

execute a MCLR Reset in software.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Start

Reset

operation

Example: RESET

After Instruction

Registers = Reset Value

Flags* = Reset Value

PIC18F2221/2321/4221/4321 FAMILY

RETFIE Return from Interrupt

Syntax: RETFIE {s}

Operands: s ∈ [0,1]

Operation: (TOS) → PC,

1 → GIE/GIEH or PEIE/GIEL;

if s = 1,

(WS) → W,

(STATUSS) → STATUS,

(BSRS) → BSR,

PCLATU, PCLATH are unchanged

Status Affected: GIE/GIEH, PEIE/GIEL

Encoding: 0000 0000 0001 000s

Description: Return from interrupt. Stack is popped

and Top-of-Stack (TOS) is loaded into

the PC. Interrupts are enabled by

setting either the high or low-priority

global interrupt enable bit. If ‘s’ = 1, the

contents of the shadow registers, WS,

STATUSS and BSRS, are loaded into

their corresponding registers, W,

STATUS and BSR. If ‘s’ = 0, no update

of these registers occurs (default).

Words: 1

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode No

operation

POP PC

from stack

Set GIEH or

GIEL

operation

Example: RETFIE 1

After Interrupt

PC = TOS

W=WS

BSR = BSRS

STATUS = STATUSS

GIE/GIEH, PEIE/GIEL = 1

RETLW Return Literal to W

Syntax: RETLW k

Operands: 0 ≤ k ≤ 255

Operation: k → W,

(TOS) → PC,

PCLATU, PCLATH are unchanged

Status Affected: None

Encoding: 0000 1100 kkkk kkkk

Description: W is loaded with the eight-bit literal ‘k’.

The program counter is loaded from the

top of the stack (the return address).

The high address latch (PCLATH)

remains unchanged.

Words: 1

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

literal ‘k’

Process

Data

POP PC

from stack,

Write to W

operation

Example:

CALL TABLE ; W contains table

; offset value

; W now has

; table value

TABLE

ADDWF PCL ; W = offset

RETLW k0 ; Begin table

RETLW k1 ;

RETLW kn ; End of table

Before Instruction

W = 07h

After Instruction

W = value of kn

PIC18F2221/2321/4221/4321 FAMILY

RETURN Return from Subroutine

Syntax: RETURN {s}

Operands: s ∈ [0,1]

Operation: (TOS) → PC;

if s = 1,

(WS) → W,

(STATUSS) → STATUS,

(BSRS) → BSR,

PCLATU, PCLATH are unchanged

Status Affected: None

Encoding: 0000 0000 0001 001s

Description: Return from subroutine. The stack is

popped and the top of the stack (TOS)

is loaded into the program counter. If

‘s’= 1, the contents of the shadow

registers, WS, STATUSS and BSRS,

are loaded into their corresponding

registers, W, STATUS and BSR. If

‘s’ = 0, no update of these registers

occurs (default).

Words: 1

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode No

operation

Process

Data

POP PC

from stack

operation

Example: RETURN

After Instruction:

PC = TOS

RLCF Rotate Left f through Carry

Syntax: RLCF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f<n>) → dest<n + 1>,

(f<7>) → C,

Status Affected: C, N, Z

Encoding: 0011 01da ffff ffff

Description: The contents of register ‘f’ are rotated

one bit to the left through the Carry

flag. If ‘d’ is ‘0’, the result is placed in

W. If ‘d’ is ‘1’, the result is stored back

in register ‘f’ (default).

If ‘a’ is ‘0’, the Access Bank is

selected. If ‘a’ is ‘1’, the BSR is used to

select the GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction

operates in Indexed Literal Offset

Addressing mode whenever

f ≤ 95 (5Fh). See Section 25.2.3

“Byte-Oriented and Bit-Oriented

Instructions in Indexed Literal Offset

Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: RLCF REG, 0, 0

Before Instruction

REG = 1110 0110

C=0

After Instruction

REG = 1110 0110

W=1100 1100

C=1

Cregister f

PIC18F2221/2321/4221/4321 FAMILY

RLNCF Rotate Left f (No Carry)

Syntax: RLNCF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f<n>) → dest<n + 1>,

(f<7>) → dest<0>

Status Affected: N, Z

Encoding: 0100 01da ffff ffff

Description: The contents of register ‘f’ are rotated

one bit to the left. If ‘d’ is ‘0’, the result

is placed in W. If ‘d’ is ‘1’, the result is

stored back in register ‘f’ (default).

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: RLNCF REG, 1, 0

Before Instruction

REG = 1010 1011

After Instruction

REG = 0101 0111

RRCF Rotate Right f through Carry

Syntax: RRCF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f<n>) → dest<n – 1>,

(f<0>) → C,

Status Affected: C, N, Z

Encoding: 0011 00da ffff ffff

Description: The contents of register ‘f’ are rotated

one bit to the right through the Carry

flag. If ‘d’ is ‘0’, the result is placed in W.

If ‘d’ is ‘1’, the result is placed back in

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: RRCF REG, 0, 0

Before Instruction

REG = 1110 0110

C=0

After Instruction

REG = 1110 0110

W=0111 0011

C=0

Cregister f

PIC18F2221/2321/4221/4321 FAMILY

RRNCF Rotate Right f (No Carry)

Syntax: RRNCF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f<n>) → dest<n – 1>,

(f<0>) → dest<7>

Status Affected: N, Z

Encoding: 0100 00da ffff ffff

Description: The contents of register ‘f’ are rotated

one bit to the right. If ‘d’ is ‘0’, the result

is placed in W. If ‘d’ is ‘1’, the result is

placed back in register ‘f’ (default).

If ‘a’ is ‘0’, the Access Bank will be

selected, overriding the BSR value. If ‘a’

is ‘1’, then the bank will be selected as

per the BSR value (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example 1: RRNCF REG, 1, 0

Before Instruction

REG = 1101 0111

After Instruction

REG = 1110 1011

Example 2: RRNCF REG, 0, 0

Before Instruction

W=?

REG = 1101 0111

After Instruction

W=1110 1011

REG = 1101 0111

SETF Set f

Syntax: SETF f {,a}

Operands: 0 ≤ f ≤ 255

a ∈ [0,1]

Operation: FFh → f

Status Affected: None

Encoding: 0110 100a ffff ffff

Description: The contents of the specified register

are set to FFh.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write

Example: SETF REG, 1

Before Instruction

REG = 5Ah

After Instruction

REG = FFh

PIC18F2221/2321/4221/4321 FAMILY

SLEEP Enter Sleep mode

Syntax: SLEEP

Operands: None

Operation: 00h → WDT,

0 → WDT postscaler,

1 → TO,

0 → PD

Status Affected: TO, PD

Encoding: 0000 0000 0000 0011

Description: The Power-Down status bit (PD) is

cleared. The Time-out status bit (TO)

is set. Watchdog Timer and its

postscaler are cleared.

The processor is put into Sleep mode

with the oscillator stopped.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode No

operation

Process

Data

Go to

Sleep

Example: SLEEP

Before Instruction

TO =?

PD =?

After Instruction

TO =1†

PD =0

† If WDT causes wake-up, this bit is cleared.

SUBFWB Subtract f from W with Borrow

Syntax: SUBFWB f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (W) – (f) – (C) → dest

Status Affected: N, OV, C, DC, Z

Encoding: 0101 01da ffff ffff

Description: Subtract register ‘f’ and Carry flag

(borrow) from W (2’s complement

method). If ‘d’ is ‘0’, the result is stored

in W. If ‘d’ is ‘1’, the result is stored in

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example 1: SUBFWB REG, 1, 0

Before Instruction

REG = 3

W=2

C=1

After Instruction

REG = FF

W=2

C=0

Z=0

N = 1 ; result is negative

Example 2: SUBFWB REG, 0, 0

Before Instruction

REG = 2

W=5

C=1

After Instruction

REG = 2

W=3

C=1

Z=0

N = 0 ; result is positive

Example 3: SUBFWB REG, 1, 0

Before Instruction

REG = 1

W=2

C=0

After Instruction

REG = 0

W=2

C=1

Z = 1 ; result is zero

N=0

PIC18F2221/2321/4221/4321 FAMILY

SUBLW Subtract W from Literal

Syntax: SUBLW k

Operands: 0 ≤ k ≤ 255

Operation: k – (W) → W

Status Affected: N, OV, C, DC, Z

Encoding: 0000 1000 kkkk kkkk

Description W is subtracted from the eight-bit

literal ‘k’. The result is placed in W.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

literal ‘k’

Process

Data

Write to W

Example 1: SUBLW 02h

Before Instruction

W = 01h

C=?

After Instruction

W = 01h

C = 1 ; result is positive

Z=0

N=0

Example 2: SUBLW 02h

Before Instruction

W = 02h

C=?

After Instruction

W = 00h

C = 1 ; result is zero

Z=1

N=0

Example 3: SUBLW 02h

Before Instruction

W = 03h

C=?

After Instruction

W = FFh ; (2’s complement)

C = 0 ; result is negative

Z=0

N=1

SUBWF Subtract W from f

Syntax: SUBWF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f) – (W) → dest

Status Affected: N, OV, C, DC, Z

Encoding: 0101 11da ffff ffff

Description: Subtract W from register ‘f’ (2’s

complement method). If ‘d’ is ‘0’, the

result is stored in W. If ‘d’ is ‘1’, the

result is stored back in register ‘f’

(default).

If ‘a’ is ‘0’, the Access Bank is

selected. If ‘a’ is ‘1’, the BSR is used

to select the GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction

operates in Indexed Literal Offset

Addressing mode whenever

f ≤ 95 (5Fh). See Section 25.2.3

“Byte-Oriented and Bit-Oriented

Instructions in Indexed Literal Offset

Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example 1: SUBWF REG, 1, 0

Before Instruction

REG = 3

W=2

C=?

After Instruction

REG = 1

W=2

C = 1 ; result is positive

Z=0

N=0

Example 2: SUBWF REG, 0, 0

Before Instruction

REG = 2

W=2

C=?

After Instruction

REG = 2

W=0

C = 1 ; result is zero

Z=1

N=0

Example 3: SUBWF REG, 1, 0

Before Instruction

REG = 1

W=2

C=?

After Instruction

REG = FFh ;(2’s complement)

W=2

C = 0 ; result is negative

Z=0

N=1

PIC18F2221/2321/4221/4321 FAMILY

SUBWFB Subtract W from f with Borrow

Syntax: SUBWFB f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f) – (W) – (C) → dest

Status Affected: N, OV, C, DC, Z

Encoding: 0101 10da ffff ffff

Description: Subtract W and the Carry flag (borrow)

from register ‘f’ (2’s complement

method). If ‘d’ is ‘0’, the result is stored

in W. If ‘d’ is ‘1’, the result is stored back

in register ‘f’ (default).

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example 1: SUBWFB REG, 1, 0

Before Instruction

REG = 19h (0001 1001)

W=0Dh(0000 1101)

C=1

After Instruction

REG = 0Ch (0000 1011)

W=0Dh(0000 1101)

C=1

Z=0

N = 0 ; result is positive

Example 2: SUBWFB REG, 0, 0

Before Instruction

REG = 1Bh (0001 1011)

W=1Ah(0001 1010)

C=0

After Instruction

REG = 1Bh (0001 1011)

W = 00h

C=1

Z = 1 ; result is zero

N=0

Example 3: SUBWFB REG, 1, 0

Before Instruction

REG = 03h (0000 0011)

W=0Eh(0000 1101)

C=1

After Instruction

REG = F5h (1111 0100)

; [2’s comp]

W=0Eh(0000 1101)

C=0

Z=0

N = 1 ; result is negative

SWAPF Swap f

Syntax: SWAPF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (f<3:0>) → dest<7:4>,

(f<7:4>) → dest<3:0>

Status Affected: None

Encoding: 0011 10da ffff ffff

Description: The upper and lower nibbles of register

‘f’ are exchanged. If ‘d’ is ‘0’, the result

is placed in W. If ‘d’ is ‘1’, the result is

placed in register ‘f’ (default).

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: SWAPF REG, 1, 0

Before Instruction

REG = 53h

After Instruction

REG = 35h

PIC18F2221/2321/4221/4321 FAMILY

TBLRD Table Read

Syntax: TBLRD ( *; *+; *-; +*)

Operands: None

Operation: if TBLRD *,

(Prog Mem (TBLPTR)) → TABLAT,

TBLPTR – No Change;

if TBLRD *+,

(Prog Mem (TBLPTR)) → TABLAT,

(TBLPTR) + 1 → TBLPTR;

if TBLRD *-,

(Prog Mem (TBLPTR)) → TABLAT,

(TBLPTR) – 1 → TBLPTR;

if TBLRD +*,

(TBLPTR) + 1 → TBLPTR,

(Prog Mem (TBLPTR)) → TABLAT

Status Affected: None

Encoding: 0000 0000 0000 10nn

nn=0 *

=1 *+

=2 *-

=3 +*

Description: This instruction is used to read the contents

of Program Memory (P.M.). To address the

program memory, a pointer called Table

Pointer (TBLPTR) is used.

The TBLPTR (a 21-bit pointer) points to

each byte in the program memory. TBLPTR

has a 2-Mbyte address range.

TBLPTR[0] = 0: Least Significant Byte of

Program Memory Word

TBLPTR[0] = 1: Most Significant Byte of

Program Memory Word

The TBLRD instruction can modify the value

of TBLPTR as follows:

• no change

• post-increment

• post-decrement

• pre-increment

Words: 1

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode No

operation

No operation

(Read Program

Memory)

operation

No operation

(Write

TABLAT)

TBLRD Table Read (Continued)

Example 1: TBLRD *+ ;

Before Instruction

TABLAT = 55h

TBLPTR = 00A356h

MEMORY (00A356h) = 34h

After Instruction

TABLAT = 34h

TBLPTR = 00A357h

Example 2: TBLRD +* ;

Before Instruction

TABLAT = AAh

TBLPTR = 01A357h

MEMORY (01A357h) = 12h

MEMORY (01A358h) = 34h

After Instruction

TABLAT = 34h

TBLPTR = 01A358h

PIC18F2221/2321/4221/4321 FAMILY

TBLWT Table Write

Syntax: TBLWT ( *; *+; *-; +*)

Operands: None

Operation: if TBLWT*,

(TABLAT) → Holding Register,

TBLPTR – No Change;

if TBLWT*+,

(TABLAT) → Holding Register,

(TBLPTR) + 1 → TBLPTR;

if TBLWT*-,

(TABLAT) → Holding Register,

(TBLPTR) – 1 → TBLPTR;

if TBLWT+*,

(TBLPTR) + 1 → TBLPTR,

(TABLAT) → Holding Register

Status Affected: None

Encoding: 0000 0000 0000 11nn

nn=0 *

=1 *+

=2 *-

=3 +*

Description: This instruction uses the 3 LSBs of

TBLPTR to determine which of the

8 holding registers the TABLAT is written

to. The holding registers are used to

program the contents of Program

Memory (P.M.). (Refer to Section 7.0

“Flash Program Memory” for additional

details on programming Flash memory.)

The TBLPTR (a 21-bit pointer) points to

each byte in the program memory.

TBLPTR has a 2-Mbyte address range.

The LSb of the TBLPTR selects which

byte of the program memory location to

access.

TBLPTR[0] = 0: Least Significant Byte

of Program Memory

Word

TBLPTR[0] = 1: Most Significant Byte

of Program Memory

Word

The TBLWT instruction can modify the

value of TBLPTR as follows:

• no change

• post-increment

• post-decrement

• pre-increment

Words: 1

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode No

operation

(Read

TABLAT)

operation

(Write to

Holding

TBLWT Table Write (Continued)

Example 1: TBLWT *+;

Before Instruction

TABLAT = 55h

TBLPTR = 00A356h

HOLDING REGISTER

(00A356h) = FFh

After Instructions (table write completion)

TABLAT = 55h

TBLPTR = 00A357h

HOLDING REGISTER

(00A356h) = 55h

Example 2: TBLWT +*;

Before Instruction

TABLAT = 34h

TBLPTR = 01389Ah

HOLDING REGISTER

(01389Ah) = FFh

HOLDING REGISTER

(01389Bh) = FFh

After Instruction (table write completion)

TABLAT = 34h

TBLPTR = 01389Bh

HOLDING REGISTER

(01389Ah) = FFh

HOLDING REGISTER

(01389Bh) = 34h

PIC18F2221/2321/4221/4321 FAMILY

TSTFSZ Test f, Skip if 0

Syntax: TSTFSZ f {,a}

Operands: 0 ≤ f ≤ 255

a ∈ [0,1]

Operation: skip if f = 0

Status Affected: None

Encoding: 0110 011a ffff ffff

Description: If ‘f’ = 0, the next instruction fetched

during the current instruction execution

is discarded and a NOP is executed,

making this a two-cycle instruction.

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1(2)

Note: 3 cycles if skip and followed

by a 2-word instruction.

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

operation

If skip:

Q1 Q2 Q3 Q4

operation

If skip and followed by 2-word instruction:

Q1 Q2 Q3 Q4

operation

Example: HERE TSTFSZ CNT, 1

NZERO :

ZERO :

Before Instruction

PC = Address (HERE)

After Instruction

If CNT = 00h,

PC = Address (ZERO)

If CNT ≠00h,

PC = Address (NZERO)

XORLW Exclusive OR Literal with W

Syntax: XORLW k

Operands: 0 ≤ k ≤ 255

Operation: (W) .XOR. k → W

Status Affected: N, Z

Encoding: 0000 1010 kkkk kkkk

Description: The contents of W are XORed with

the 8-bit literal ‘k’. The result is placed

in W.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

literal ‘k’

Process

Data

Write to W

Example: XORLW 0AFh

Before Instruction

W=B5h

After Instruction

W=1Ah

PIC18F2221/2321/4221/4321 FAMILY

XORWF Exclusive OR W with f

Syntax: XORWF f {,d {,a}}

Operands: 0 ≤ f ≤ 255

d ∈ [0,1]

a ∈ [0,1]

Operation: (W) .XOR. (f) → dest

Status Affected: N, Z

Encoding: 0001 10da ffff ffff

Description: Exclusive OR the contents of W with

in W. If ‘d’ is ‘1’, the result is stored back

in the register ‘f’ (default).

If ‘a’ is ‘0’, the Access Bank is selected.

If ‘a’ is ‘1’, the BSR is used to select the

GPR bank (default).

If ‘a’ is ‘0’ and the extended instruction

set is enabled, this instruction operates

in Indexed Literal Offset Addressing

mode whenever f ≤ 95 (5Fh). See

Section 25.2.3 “Byte-Oriented and

Bit-Oriented Instructions in Indexed

Literal Offset Mode” for details.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: XORWF REG, 1, 0

Before Instruction

REG = AFh

W=B5h

After Instruction

REG = 1Ah

W=B5h

PIC18F2221/2321/4221/4321 FAMILY

25.2 Extended Instruction Set

In addition to the standard 75 instructions of the PIC18

instruction set, PIC18F2221/2321/4221/4321 family

devices also provide an optional extension to the core

CPU functionality. The added features include eight

additional instructions that augment indirect and

indexed addressing operations and the implementation

of Indexed Literal Offset Addressing mode for many of

the standard PIC18 instructions.

The additional features of the extended instruction set

are disabled by default. To enable them, users must set

the XINST Configuration bit.

The instructions in the extended set (with the exception

of CALLW, MOVSF and MOVSS) can all be classified as

literal operations, which either manipulate the File

Select Registers, or use them for indexed addressing.

Two of the instructions, ADDFSR and SUBFSR, each

have an additional special instantiation for using FSR2.

These versions (ADDULNK and SUBULNK) allow for

automatic return after execution.

The extended instructions are specifically implemented

to optimize re-entrant program code (that is, code that

is recursive or that uses a software stack) written in

high-level languages, particularly C. Among other

things, they allow users working in high-level

languages to perform certain operations on data

structures more efficiently. These include:

• Dynamic allocation and deallocation of software

stack space when entering and leaving

subroutines

• Function Pointer invocation

• Software Stack Pointer manipulation

• Manipulation of variables located in a software

stack

A summary of the instructions in the extended instruction

set is provided in Table 25-3. Detailed descriptions are

provided in Section 25.2.2 “Extended Instruction

Set”. The opcode field descriptions in Table 25-1

(page 280) apply to both the standard and extended

PIC18 instruction sets.

25.2.1 EXTENDED INSTRUCTION SYNTAX

Most of the extended instructions use indexed

arguments, using one of the File Select Registers and

some offset to specify a source or destination register.

When an argument for an instruction serves as part of

indexed addressing, it is enclosed in square brackets

(“[ ]”). This is done to indicate that the argument is used

as an index or offset. The MPASM™ Assembler will

flag an error if it determines that an index or offset value

is not bracketed.

When the extended instruction set is enabled, brackets

are also used to indicate index arguments in byte-

oriented and bit-oriented instructions. This is in addition

to other changes in their syntax. For more details, see

Section 25.2.3.1 “Extended Instruction Syntax with

Standard PIC18 Commands”.

TABLE 25-3: EXTENSIONS TO THE PIC18 INSTRUCTION SET

Note: The instruction set extension and the

Indexed Literal Offset Addressing mode

were designed for optimizing applications

written in C; the user may likely never use

these instructions directly in the assembler.

The syntax for these commands is

provided as a reference for users who may

be reviewing code that has been generated

by a compiler.

Note: In the past, square brackets have been

used to denote optional arguments in the

PIC18 and earlier instruction sets. In this

text and going forward, optional

arguments are denoted by braces (“{ }”).

Mnemonic,

Operands Description Cycles

16-Bit Instruction Word Status

Affected

MSb LSb

ADDFSR

ADDULNK

CALLW

MOVSF

MOVSS

PUSHL

SUBFSR

SUBULNK

f, k

zs, fd

zs, zd

f, k

Add Literal to FSR

Add Literal to FSR2 and Return

Call Subroutine using WREG

Move zs (source) to 1st Word

fd (destination) 2nd Word

Move zs (source) to 1st word

zd (destination) 2nd Word

Store Literal at FSR2,

Decrement FSR2

Subtract Literal from FSR

Subtract Literal from FSR2 and

Return

1110

0000

1110

1111

1110

1111

1110

1000

0000

1011

ffff

1011

xxxx

1010

1001

ffkk

11kk

0001

0zzz

ffff

1zzz

xzzz

kkkk

ffkk

11kk

kkkk

0100

zzzz

ffff

zzzz

kkkk

None

PIC18F2221/2321/4221/4321 FAMILY

25.2.2 EXTENDED INSTRUCTION SET

ADDFSR Add Literal to FSR

Syntax: ADDFSR f, k

Operands: 0 ≤ k ≤ 63

f ∈ [ 0, 1, 2 ]

Operation: FSR(f) + k → FSR(f)

Status Affected: None

Encoding: 1110 1000 ffkk kkkk

Description: The 6-bit literal ‘k’ is added to the

contents of the FSR specified by ‘f’.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

literal ‘k’

Process

Data

Write to

FSR

Example: ADDFSR 2, 23h

Before Instruction

FSR2 = 03FFh

After Instruction

FSR2 = 0422h

ADDULNK Add Literal to FSR2 and Return

Syntax: ADDULNK k

Operands: 0 ≤ k ≤ 63

Operation: FSR2 + k → FSR2,

(TOS) → PC

Status Affected: None

Encoding: 1110 1000 11kk kkkk

Description: The 6-bit literal ‘k’ is added to the

contents of FSR2. A RETURN is then

executed by loading the PC with the

TOS.

The instruction takes two cycles to

execute; a NOP is performed during the

second cycle.

This may be thought of as a special

case of the ADDFSR instruction, where

f = 3 (binary ‘11’); it operates only on

FSR2.

Words: 1

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

literal ‘k’

Process

Data

Write to

FSR

Operation

Example: ADDULNK 23h

Before Instruction

FSR2 = 03FFh

PC = 0100h

After Instruction

FSR2 = 0422h

PC = (TOS)

Note: All PIC18 instructions may take an optional label argument preceding the instruction mnemonic for use in

symbolic addressing. If a label is used, the instruction syntax then becomes: {label} instruction argument(s).

PIC18F2221/2321/4221/4321 FAMILY

CALLW Subroutine Call Using WREG

Syntax: CALLW

Operands: None

Operation: (PC + 2) → TOS,

(W) → PCL,

(PCLATH) → PCH,

(PCLATU) → PCU

Status Affected: None

Encoding: 0000 0000 0001 0100

Description First, the return address (PC + 2) is

pushed onto the return stack. Next, the

contents of W are written to PCL; the

existing value is discarded. Then, the

contents of PCLATH and PCLATU are

latched into PCH and PCU,

respectively. The second cycle is

executed as a NOP instruction while the

new next instruction is fetched.

Unlike CALL, there is no option to

update W, STATUS or BSR.

Words: 1

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

WREG

PUSH PC to

stack

operation

Example: HERE CALLW

Before Instruction

PC = address (HERE)

PCLATH = 10h

PCLATU = 00h

W = 06h

After Instruction

PC = 001006h

TOS = address (HERE + 2)

PCLATH = 10h

PCLATU = 00h

W = 06h

MOVSF Move Indexed to f

Syntax: MOVSF [zs], fd

Operands: 0 ≤ zs ≤ 127

0 ≤ fd ≤ 4095

Operation: ((FSR2) + zs) → fd

Status Affected: None

Encoding:

1st word (source)

2nd word (destin.)

1110

1111

1011

ffff

0zzz

ffff

zzzzs

ffffd

Description: The contents of the source register are

moved to destination register ‘fd’. The

actual address of the source register is

determined by adding the 7-bit literal

offset ‘zs’ in the first word to the value of

FSR2. The address of the destination

‘fd’ in the second word. Both addresses

can be anywhere in the 4096-byte data

space (000h to FFFh).

The MOVSF instruction cannot use the

PCL, TOSU, TOSH or TOSL as the

destination register.

If the resultant source address points to

an indirect addressing register, the

value returned will be 00h.

Words: 2

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Determine

source addr

Determine

source addr

Read

source reg

Decode No

operation

No dummy

read

operation

Write

(dest)

Example: MOVSF [05h], REG2

Before Instruction

FSR2 = 80h

Contents

of 85h = 33h

REG2 = 11h

After Instruction

FSR2 = 80h

Contents

of 85h = 33h

REG2 = 33h

PIC18F2221/2321/4221/4321 FAMILY

MOVSS Move Indexed to Indexed

Syntax: MOVSS [zs], [zd]

Operands: 0 ≤ zs ≤ 127

0 ≤ zd ≤ 127

Operation: ((FSR2) + zs) → ((FSR2) + zd)

Status Affected: None

Encoding:

1st word (source)

2nd word (dest.)

1110

1111

1011

xxxx

1zzz

xzzz

zzzzs

zzzzd

Description The contents of the source register are

moved to the destination register. The

addresses of the source and destination

registers are determined by adding the

7-bit literal offsets ‘zs’ or ‘zd’,

respectively, to the value of FSR2. Both

registers can be located anywhere in

the 4096-byte data memory space

(000h to FFFh).

The MOVSS instruction cannot use the

PCL, TOSU, TOSH or TOSL as the

destination register.

If the resultant source address points to

an indirect addressing register, the

value returned will be 00h. If the

resultant destination address points to

an indirect addressing register, the

instruction will execute as a NOP.

Words: 2

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Determine

source addr

Determine

source addr

Read

source reg

Decode Determine

dest addr

Determine

dest addr

Write

to dest reg

Example: MOVSS [05h], [06h]

Before Instruction

FSR2 = 80h

Contents

of 85h = 33h

Contents

of 86h = 11h

After Instruction

FSR2 = 80h

Contents

of 85h = 33h

Contents

of 86h = 33h

PUSHL

Store Literal at FSR2, Decrement FSR2

Syntax: PUSHL k

Operands: 0 ≤ k ≤ 255

Operation: k → (FSR2),

FSR2 – 1 → FSR2

Status Affected: None

Encoding: 1111 1010 kkkk kkkk

Description: The 8-bit literal ‘k’ is written to the data

memory address specified by FSR2. FSR2

is decremented by 1 after the operation.

This instruction allows users to push values

onto a software stack.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read ‘k’ Process

data

Write to

destination

Example: PUSHL 08h

Before Instruction

FSR2H:FSR2L = 01ECh

Memory (01ECh) = 00h

After Instruction

FSR2H:FSR2L = 01EBh

Memory (01ECh) = 08h

PIC18F2221/2321/4221/4321 FAMILY

SUBFSR Subtract Literal from FSR

Syntax: SUBFSR f, k

Operands: 0 ≤ k ≤ 63

f ∈ [ 0, 1, 2 ]

Operation: FSR(f – k) → FSR(f)

Status Affected: None

Encoding: 1110 1001 ffkk kkkk

Description: The 6-bit literal ‘k’ is subtracted from

the contents of the FSR specified

by ‘f’.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: SUBFSR 2, 23h

Before Instruction

FSR2 = 03FFh

After Instruction

FSR2 = 03DCh

SUBULNK

Subtract Literal from FSR2 and Return

Syntax: SUBULNK k

Operands: 0 ≤ k ≤ 63

Operation: FSR2 – k → FSR2,

(TOS) → PC

Status

Affected:

None

Encoding: 1110 1001 11kk kkkk

Description: The 6-bit literal ‘k’ is subtracted from the

contents of the FSR2. A RETURN is then

executed by loading the PC with the TOS.

The instruction takes two cycles to

execute; a NOP is performed during the

second cycle.

This may be thought of as a special case of

the SUBFSR instruction, where f = 3 (binary

‘11’); it operates only on FSR2.

Words: 1

Cycles: 2

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Operation

Example: SUBULNK 23h

Before Instruction

FSR2 = 03FFh

PC = 0100h

After Instruction

FSR2 = 03DCh

PC = (TOS)

PIC18F2221/2321/4221/4321 FAMILY

25.2.3 BYTE-ORIENTED AND

BIT-ORIENTED INSTRUCTIONS IN

INDEXED LITERAL OFFSET MODE

In addition to eight new commands in the extended set,

enabling the extended instruction set also enables

Indexed Literal Offset Addressing mode (Section 6.5.1

“Indexed Addressing with Literal Offset”). This has

a significant impact on the way that many commands of

the standard PIC18 instruction set are interpreted.

When the extended set is disabled, addresses embed-

ded in opcodes are treated as literal memory locations:

either as a location in the Access Bank (‘a’ = 0) or in a

GPR bank designated by the BSR (‘a’ = 1). When the

extended instruction set is enabled and ‘a’ = 0,

however, a file register argument of 5Fh or less is

interpreted as an offset from the pointer value in FSR2

and not as a literal address. For practical purposes, this

means that all instructions that use the Access RAM bit

as an argument – that is, all byte-oriented and bit-

oriented instructions, or almost half of the core PIC18

instructions – may behave differently when the

extended instruction set is enabled.

When the content of FSR2 is 00h, the boundaries of the

Access RAM are essentially remapped to their original

values. This may be useful in creating backward

compatible code. If this technique is used, it may be

necessary to save the value of FSR2 and restore it

when moving back and forth between C and assembly

routines in order to preserve the Stack Pointer. Users

must also keep in mind the syntax requirements of the

extended instruction set (see Section 25.2.3.1

“Extended Instruction Syntax with Standard PIC18

Commands”).

Although the Indexed Literal Offset Addressing mode

can be very useful for dynamic stack and pointer

manipulation, it can also be very annoying if a simple

arithmetic operation is carried out on the wrong

programming must keep in mind that, when the

extended instruction set is enabled, register addresses

of 5Fh or less are used for Indexed Literal Offset

Addressing mode.

Representative examples of typical byte-oriented and

bit-oriented instructions in the Indexed Literal Offset

Addressing mode are provided on the following page to

show how execution is affected. The operand

conditions shown in the examples are applicable to all

instructions of these types.

25.2.3.1 Extended Instruction Syntax with

Standard PIC18 Commands

When the extended instruction set is enabled, the file

bit-oriented commands is replaced with the literal offset

value, ‘k’. As already noted, this occurs only when ‘f’ is

less than or equal to 5Fh. When an offset value is used,

it must be indicated by square brackets (“[ ]”). As with

the extended instructions, the use of brackets indicates

to the compiler that the value is to be interpreted as an

index or an offset. Omitting the brackets, or using a

value greater than 5Fh within brackets, will generate an

error in the MPASM Assembler.

If the index argument is properly bracketed for Indexed

Literal Offset Addressing mode, the Access RAM

argument is never specified; it will automatically be

assumed to be ‘0’. This is in contrast to standard

operation (extended instruction set disabled) when ‘a’

is set on the basis of the target address. Declaring the

Access RAM bit in this mode will also generate an error

in the MPASM Assembler.

The destination argument, ‘d’, functions as before.

In the latest versions of the MPASM Assembler,

language support for the extended instruction set must

be explicitly invoked. This is done with either the

command line option, /y, or the PE directive in the

source listing.

25.2.4 CONSIDERATIONS WHEN

ENABLING THE EXTENDED

INSTRUCTION SET

It is important to note that the extensions to the instruc-

tion set may not be beneficial to all users. In particular,

users who are not writing code that uses a software

stack may not benefit from using the extensions to the

instruction set.

Additionally, the Indexed Literal Offset Addressing

mode may create issues with legacy applications

written to the PIC18 assembler. This is because

instructions in the legacy code may attempt to address

registers in the Access Bank below 5Fh. Since these

addresses are interpreted as literal offsets to FSR2

when the instruction set extension is enabled, the

application may read or write to the wrong data

addresses.

When porting an application to the PIC18F2221/2321/

4221/4321 family, it is very important to consider the

type of code. A large, re-entrant application that is

written in ‘C’ and would benefit from efficient

compilation will do well when using the instruction set

extensions. Legacy applications that heavily use the

Access Bank will most likely not benefit from using the

extended instruction set.

Note: Enabling the PIC18 instruction set

extension may cause legacy applications

to behave erratically or fail entirely.

PIC18F2221/2321/4221/4321 FAMILY

ADDWF ADD W to Indexed

(Indexed Literal Offset mode)

Syntax: ADDWF [k] {,d}

Operands: 0 ≤ k ≤ 95

d ∈ [0,1]

Operation: (W) + ((FSR2) + k) → dest

Status Affected: N, OV, C, DC, Z

Encoding: 0010 01d0 kkkk kkkk

Description: The contents of W are added to the

contents of the register indicated by

FSR2, offset by the value ‘k’.

If ‘d’ is ‘0’, the result is stored in W. If ‘d’

is ‘1’, the result is stored back in

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read ‘k’ Process

Data

Write to

destination

Example: ADDWF [OFST] , 0

Before Instruction

W = 17h

OFST = 2Ch

FSR2 = 0A00h

Contents

of 0A2Ch = 20h

After Instruction

W = 37h

Contents

of 0A2Ch = 20h

BSF Bit Set Indexed

(Indexed Literal Offset mode)

Syntax: BSF [k], b

Operands: 0 ≤ f ≤ 95

0 ≤ b ≤ 7

Operation: 1 → ((FSR2) + k)

Status Affected: None

Encoding: 1000 bbb0 kkkk kkkk

Description: Bit ‘b’ of the register indicated by FSR2,

offset by the value ‘k’, is set.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read

Process

Data

Write to

destination

Example: BSF [FLAG_OFST], 7

Before Instruction

FLAG_OFST = 0Ah

FSR2 = 0A00h

Contents

of 0A0Ah = 55h

After Instruction

Contents

of 0A0Ah = D5h

SETF Set Indexed

(Indexed Literal Offset mode)

Syntax: SETF [k]

Operands: 0 ≤ k ≤ 95

Operation: FFh → ((FSR2) + k)

Status Affected: None

Encoding: 0110 1000 kkkk kkkk

Description: The contents of the register indicated

by FSR2, offset by ‘k’, are set to FFh.

Words: 1

Cycles: 1

Q Cycle Activity:

Q1 Q2 Q3 Q4

Decode Read ‘k’ Process

Data

Write

Example: SETF [OFST]

Before Instruction

OFST = 2Ch

FSR2 = 0A00h

Contents

of 0A2Ch = 00h

After Instruction

Contents

of 0A2Ch = FFh

PIC18F2221/2321/4221/4321 FAMILY

25.2.5 SPECIAL CONSIDERATIONS WITH

MICROCHIP MPLAB® IDE TOOLS

The latest versions of Microchip’s software tools have

been designed to fully support the extended instruction

set of the PIC18F2221/2321/4221/4321 family family of

devices. This includes the MPLAB C18 C Compiler,

MPASM Assembly language and MPLAB Integrated

Development Environment (IDE).

When selecting a target device for software

development, MPLAB IDE will automatically set default

Configuration bits for that device. The default setting for

the XINST Configuration bit is ‘0’, disabling the

extended instruction set and Indexed Literal Offset

Addressing mode. For proper execution of applications

developed to take advantage of the extended

instruction set, XINST must be set during

programming.

To develop software for the extended instruction set,

the user must enable support for the instructions and

the Indexed Addressing mode in their language tool(s).

Depending on the environment being used, this may be

done in several ways:

• A menu option, or dialog box within the

environment, that allows the user to configure the

language tool and its settings for the project

• A command line option

• A directive in the source code

These options vary between different compilers,

assemblers and development environments. Users are

encouraged to review the documentation accompany-

ing their development systems for the appropriate

information.

PIC18F2221/2321/4221/4321 FAMILY

26.0 DEVELOPMENT SUPPORT

The PIC® microcontrollers and dsPIC® digital signal

controllers are supported with a full range of software

and hardware development tools:

• Integrated Development Environment

- MPLAB® IDE Software

• Compilers/Assemblers/Linkers

- MPLAB C Compiler for Various Device

Families

- HI-TECH C for Various Device Families

- MPASMTM Assembler

-MPLINK

TM Object Linker/

MPLIBTM Object Librarian

- MPLAB Assembler/Linker/Librarian for

Various Device Families

• Simulators

- MPLAB SIM Software Simulator

•Emulators

- MPLAB REAL ICE™ In-Circuit Emulator

• In-Circuit Debuggers

- MPLAB ICD 3

- PICkit™ 3 Debug Express

• Device Programmers

- PICkit™ 2 Programmer

- MPLAB PM3 Device Programmer

• Low-Cost Demonstration/Development Boards,

Evaluation Kits, and Starter Kits

26.1 MPLAB Integrated Development

Environment Software

The MPLAB IDE software brings an ease of software

development previously unseen in the 8/16/32-bit

microcontroller market. The MPLAB IDE is a Windows®

operating system-based application that contains:

• A single graphical interface to all debugging tools

- Simulator

- Programmer (sold separately)

- In-Circuit Emulator (sold separately)

- In-Circuit Debugger (sold separately)

• A full-featured editor with color-coded context

• A multiple project manager

• Customizable data windows with direct edit of

contents

• High-level source code debugging

• Mouse over variable inspection

• Drag and drop variables from source to watch

windows

• Extensive on-line help

• Integration of select third party tools, such as

IAR C Compilers

The MPLAB IDE allows you to:

• Edit your source files (either C or assembly)

• One-touch compile or assemble, and download to

emulator and simulator tools (automatically

updates all project information)

• Debug using:

- Source files (C or assembly)

- Mixed C and assembly

- Machine code

MPLAB IDE supports multiple debugging tools in a

single development paradigm, from the cost-effective

simulators, through low-cost in-circuit debuggers, to

full-featured emulators. This eliminates the learning

curve when upgrading to tools with increased flexibility

and power.

PIC18F2221/2321/4221/4321 FAMILY

26.2 MPLAB C Compilers for Various

Device Families

The MPLAB C Compiler code development systems

are complete ANSI C compilers for Microchip’s PIC18,

PIC24 and PIC32 families of microcontrollers and the

dsPIC30 and dsPIC33 families of digital signal control-

lers. These compilers provide powerful integration

capabilities, superior code optimization and ease of

use.

For easy source level debugging, the compilers provide

symbol information that is optimized to the MPLAB IDE

debugger.

26.3 HI-TECH C for Various Device

Families

The HI-TECH C Compiler code development systems

are complete ANSI C compilers for Microchip’s PIC

family of microcontrollers and the dsPIC family of digital

signal controllers. These compilers provide powerful

integration capabilities, omniscient code generation

and ease of use.

For easy source level debugging, the compilers provide

symbol information that is optimized to the MPLAB IDE

debugger.

The compilers include a macro assembler, linker, pre-

processor, and one-step driver, and can run on multiple

platforms.

26.4 MPASM Assembler

The MPASM Assembler is a full-featured, universal

macro assembler for PIC10/12/16/18 MCUs.

The MPASM Assembler generates relocatable object

files for the MPLINK Object Linker, Intel® standard HEX

files, MAP files to detail memory usage and symbol

reference, absolute LST files that contain source lines

and generated machine code and COFF files for

debugging.

The MPASM Assembler features include:

• Integration into MPLAB IDE projects

• User-defined macros to streamline

assembly code

• Conditional assembly for multi-purpose

source files

• Directives that allow complete control over the

assembly process

26.5 MPLINK Object Linker/

MPLIB Object Librarian

The MPLINK Object Linker combines relocatable

objects created by the MPASM Assembler and the

MPLAB C18 C Compiler. It can link relocatable objects

from precompiled libraries, using directives from a

linker script.

The MPLIB Object Librarian manages the creation and

modification of library files of precompiled code. When

a routine from a library is called from a source file, only

the modules that contain that routine will be linked in

with the application. This allows large libraries to be

used efficiently in many different applications.

The object linker/library features include:

• Efficient linking of single libraries instead of many

smaller files

• Enhanced code maintainability by grouping

related modules together

• Flexible creation of libraries with easy module

listing, replacement, deletion and extraction

26.6 MPLAB Assembler, Linker and

Librarian for Various Device

Families

MPLAB Assembler produces relocatable machine

code from symbolic assembly language for PIC24,

PIC32 and dsPIC devices. MPLAB C Compiler uses

the assembler to produce its object file. The assembler

generates relocatable object files that can then be

archived or linked with other relocatable object files and

archives to create an executable file. Notable features

of the assembler include:

• Support for the entire device instruction set

• Support for fixed-point and floating-point data

• Command line interface

• Rich directive set

• Flexible macro language

• MPLAB IDE compatibility

PIC18F2221/2321/4221/4321 FAMILY

26.7 MPLAB SIM Software Simulator

The MPLAB SIM Software Simulator allows code

development in a PC-hosted environment by simulat-

ing the PIC MCUs and dsPIC® DSCs on an instruction

level. On any given instruction, the data areas can be

examined or modified and stimuli can be applied from

a comprehensive stimulus controller. Registers can be

logged to files for further run-time analysis. The trace

buffer and logic analyzer display extend the power of

the simulator to record and track program execution,

actions on I/O, most peripherals and internal registers.

The MPLAB SIM Software Simulator fully supports

symbolic debugging using the MPLAB C Compilers,

and the MPASM and MPLAB Assemblers. The soft-

ware simulator offers the flexibility to develop and

debug code outside of the hardware laboratory envi-

ronment, making it an excellent, economical software

development tool.

26.8 MPLAB REAL ICE In-Circuit

Emulator System

MPLAB REAL ICE In-Circuit Emulator System is

Microchip’s next generation high-speed emulator for

Microchip Flash DSC and MCU devices. It debugs and

programs PIC® Flash MCUs and dsPIC® Flash DSCs

with the easy-to-use, powerful graphical user interface of

the MPLAB Integrated Development Environment (IDE),

included with each kit.

The emulator is connected to the design engineer’s PC

using a high-speed USB 2.0 interface and is connected

to the target with either a connector compatible with in-

circuit debugger systems (RJ11) or with the new high-

speed, noise tolerant, Low-Voltage Differential Signal

(LVDS) interconnection (CAT5).

The emulator is field upgradable through future firmware

downloads in MPLAB IDE. In upcoming releases of

MPLAB IDE, new devices will be supported, and new

features will be added. MPLAB REAL ICE offers signifi-

cant advantages over competitive emulators including

low-cost, full-speed emulation, run-time variable

watches, trace analysis, complex breakpoints, a rugge-

dized probe interface and long (up to three meters) inter-

connection cables.

26.9 MPLAB ICD 3 In-Circuit Debugger

System

MPLAB ICD 3 In-Circuit Debugger System is Micro-

chip's most cost effective high-speed hardware

debugger/programmer for Microchip Flash Digital Sig-

nal Controller (DSC) and microcontroller (MCU)

devices. It debugs and programs PIC® Flash microcon-

trollers and dsPIC® DSCs with the powerful, yet easy-

to-use graphical user interface of MPLAB Integrated

Development Environment (IDE).

The MPLAB ICD 3 In-Circuit Debugger probe is con-

nected to the design engineer's PC using a high-speed

USB 2.0 interface and is connected to the target with a

connector compatible with the MPLAB ICD 2 or MPLAB

REAL ICE systems (RJ-11). MPLAB ICD 3 supports all

MPLAB ICD 2 headers.

26.10 PICkit 3 In-Circuit Debugger/

Programmer and

PICkit 3 Debug Express

The MPLAB PICkit 3 allows debugging and program-

ming of PIC® and dsPIC® Flash microcontrollers at a

most affordable price point using the powerful graphical

user interface of the MPLAB Integrated Development

Environment (IDE). The MPLAB PICkit 3 is connected

to the design engineer's PC using a full speed USB

interface and can be connected to the target via an

Microchip debug (RJ-11) connector (compatible with

MPLAB ICD 3 and MPLAB REAL ICE). The connector

uses two device I/O pins and the reset line to imple-

ment in-circuit debugging and In-Circuit Serial Pro-

gramming™.

The PICkit 3 Debug Express include the PICkit 3, demo

board and microcontroller, hookup cables and CDROM

with user’s guide, lessons, tutorial, compiler and

MPLAB IDE software.

PIC18F2221/2321/4221/4321 FAMILY

26.11 PICkit 2 Development

Programmer/Debugger and

PICkit 2 Debug Express

The PICkit™ 2 Development Programmer/Debugger is

a low-cost development tool with an easy to use inter-

face for programming and debugging Microchip’s Flash

families of microcontrollers. The full featured

Windows® programming interface supports baseline

(PIC10F, PIC12F5xx, PIC16F5xx), midrange

(PIC12F6xx, PIC16F), PIC18F, PIC24, dsPIC30,

dsPIC33, and PIC32 families of 8-bit, 16-bit, and 32-bit

microcontrollers, and many Microchip Serial EEPROM

products. With Microchip’s powerful MPLAB Integrated

Development Environment (IDE) the PICkit™ 2

enables in-circuit debugging on most PIC® microcon-

trollers. In-Circuit-Debugging runs, halts and single

steps the program while the PIC microcontroller is

embedded in the application. When halted at a break-

point, the file registers can be examined and modified.

The PICkit 2 Debug Express include the PICkit 2, demo

board and microcontroller, hookup cables and CDROM

with user’s guide, lessons, tutorial, compiler and

MPLAB IDE software.

26.12 MPLAB PM3 Device Programmer

The MPLAB PM3 Device Programmer is a universal,

CE compliant device programmer with programmable

voltage verification at VDDMIN and VDDMAX for

maximum reliability. It features a large LCD display

(128 x 64) for menus and error messages and a modu-

lar, detachable socket assembly to support various

package types. The ICSP™ cable assembly is included

as a standard item. In Stand-Alone mode, the MPLAB

PM3 Device Programmer can read, verify and program

PIC devices without a PC connection. It can also set

code protection in this mode. The MPLAB PM3

connects to the host PC via an RS-232 or USB cable.

The MPLAB PM3 has high-speed communications and

optimized algorithms for quick programming of large

memory devices and incorporates an MMC card for file

storage and data applications.

26.13 Demonstration/Development

Boards, Evaluation Kits, and

Starter Kits

A wide variety of demonstration, development and

evaluation boards for various PIC MCUs and dsPIC

DSCs allows quick application development on fully func-

tional systems. Most boards include prototyping areas for

adding custom circuitry and provide application firmware

and source code for examination and modification.

The boards support a variety of features, including LEDs,

temperature sensors, switches, speakers, RS-232

interfaces, LCD displays, potentiometers and additional

EEPROM memory.

The demonstration and development boards can be

used in teaching environments, for prototyping custom

circuits and for learning about various microcontroller

applications.

In addition to the PICDEM™ and dsPICDEM™ demon-

stration/development board series of circuits, Microchip

has a line of evaluation kits and demonstration software

for analog filter design, KEELOQ® security ICs, CAN,

IrDA®, PowerSmart battery management, SEEVAL®

evaluation system, Sigma-Delta ADC, flow rate

sensing, plus many more.

Also available are starter kits that contain everything

needed to experience the specified device. This usually

includes a single application and debug capability, all

on one board.

Check the Microchip web page (www.microchip.com)

for the complete list of demonstration, development

and evaluation kits.

PIC18F2221/2321/4221/4321 FAMILY

27.0 ELECTRICAL CHARACTERISTICS

Absolute Maximum Ratings(†)

Ambient temperature under bias.............................................................................................................-40°C to +125°C

Storage temperature .............................................................................................................................. -65°C to +150°C

Voltage on any pin with respect to VSS (except VDD and MCLR) ................................................... -0.3V to (VDD + 0.3V)

Voltage on VDD with respect to VSS ......................................................................................................... -0.3V to +7.5V

Voltage on MCLR with respect to VSS (Note 2) ......................................................................................... 0V to +13.25V

Total power dissipation (Note 1) ...............................................................................................................................1.0W

Maximum current out of VSS pin ...........................................................................................................................300 mA

Maximum current into VDD pin ..............................................................................................................................250 mA

Input clamp current, IIK (VI < 0 or VI > VDD)...................................................................................................................... ±20 mA

Output clamp current, IOK (VO < 0 or VO > VDD).............................................................................................................. ±20 mA

Maximum output current sunk by any I/O pin..........................................................................................................25 mA

Maximum output current sourced by any I/O pin ....................................................................................................25 mA

Maximum current sunk by all ports .......................................................................................................................200 mA

Maximum current sourced by all ports ..................................................................................................................200 mA

Note 1: Power dissipation is calculated as follows:

Pdis = VDD x {IDD – ∑ IOH} + ∑ {(VDD – VOH) x IOH} + ∑(VOL x IOL)

2: Voltage spikes below VSS at the MCLR/VPP/RE3 pin, inducing currents greater than 80 mA, may cause

latch-up. Thus, a series resistor of 50-100Ω should be used when applying a “low” level to the MCLR/VPP/

RE3 pin, rather than pulling this pin directly to VSS.

† NOTICE: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the

device. This is a stress rating only and functional operation of the device at those or any other conditions above those

indicated in the operation listings of this specification is not implied. Exposure to maximum rating conditions for

extended periods may affect device reliability.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-1: PIC18F2221/2321/4221/4321 VOLTAGE-FREQUENCY GRAPH (INDUSTRIAL)

FIGURE 27-2: PIC18F2221/2321/4221/4321 VOLTAGE-FREQUENCY GRAPH (EXTENDED)

Frequency

Voltage

6.0V

5.5V

4.5V

4.0V

2.0V

40 MHz

5.0V

3.5V

3.0V

2.5V

4.2V

Frequency

Voltage

6.0V

5.5V

4.5V

4.0V

2.0V

25 MHz

5.0V

3.5V

3.0V

2.5V

4.2V

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-3: PIC18LF2221/2321/4221/4321 VOLTAGE-FREQUENCY GRAPH (INDUSTRIAL)

Frequency

Voltage

6.0V

5.5V

4.5V

4.0V

2.0V

25 MHz

5.0V

3.5V

3.0V

2.5V

FMAX = (9.54 MHz/V) (VDDAPPMIN – 2.0V) + 4 MHz

Note: VDDAPPMIN is the minimum voltage of the PIC® device in the application.

4 MHz

4.2V

40 MHz

PIC18F2221/2321/4221/4321 FAMILY

27.1 DC Characteristics: Supply Voltage

PIC18F2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321

(Industrial)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

PIC18F2221/2321/4221/4321

(Industrial, Extended)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Symbol Characteristic Min Typ Max Units Conditions

D001 VDD Supply Voltage

PIC18LF2X21/4X21 2.0 — 5.5 V

PIC18F2X21/4X21 4.2 —5.5 V

D001C AVDD Analog Supply Voltage VDD – 0.3V — VDD + 0.3V V

D001D AVSS Analog Ground Voltage VSS – 0.3V — VSS + 0.3V V

D002 VDR RAM Data Retention

Voltage(1)

1.5 — — V

D003 VPOR VDD Start Voltage

to Ensure Internal

Power-on Reset Signal

— — 0.7 V See section on Power-on Reset for

details

D004 SVDD VDD Rise Rate

to Ensure Internal

Power-on Reset Signal

0.05 — — V/ms See section on Power-on Reset for

details

VBOR Brown-out Reset Voltage

D005 PIC18LF2X21/4X21

BORV<1:0> = 11 2.00 2.11 2.22 V

BORV<1:0> = 10 2.65 2.79 2.93 V

D005 All devices

BORV<1:0> = 01(2) 4.11 4.33 4.55 V

BORV<1:0> = 00 4.36 4.59 4.82 V

Legend: Shading of rows is to assist in readability of the table.

Note 1: This is the limit to which VDD can be lowered in Sleep mode, or during a device Reset, without losing RAM data.

2: With BOR enabled, full-speed operation (FOSC = 40 MHz) is supported until a BOR occurs. This is valid although

VDD may be below the minimum voltage for this frequency.

PIC18F2221/2321/4221/4321 FAMILY

27.2 DC Characteristics: Power-Down and Supply Current

PIC18F2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321

(Industrial)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

PIC18F2221/2321/4221/4321

(Industrial, Extended)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Device Typ Max Units Conditions

Power-Down Current (IPD)(1)

PIC18LF2X21/4X21 0.5 0.7 μA -40°C VDD = 2.0V

(Sleep mode)

0.5 0.7 μA +25°C

0.5 1.7 μA +85°C

PIC18LF2X21/4X21 0.6 0.9 μA-40°C VDD = 3.0V

(Sleep mode)

0.6 0.9 μA +25°C

0.6 1.9 μA +85°C

All Devices 0.9 2.0 μA-40°C

VDD = 5.0V

(Sleep mode)

0.9 2.0 μA +25°C

0.9 6.5 μA +85°C

Extended Devices Only 7.5 70 μA +125°C

Legend: Shading of rows is to assist in readability of the table.

Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured

with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that

add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).

2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin

loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have

an impact on the current consumption.

The test conditions for all IDD measurements in active operation mode are:

OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;

MCLR = VDD; WDT enabled/disabled as specified.

3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.

4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less

than the sum of both specifications.

5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.

PIC18F2221/2321/4221/4321 FAMILY

Supply Current (IDD)(2)

PIC18LF2X21/4X21 13 19 μA-40°C

VDD = 2.0V

FOSC = 31 kHz

(RC_RUN mode,

INTRC source)

13 19 μA+25°C

13 17 μA+85°C

PIC18LF2X21/4X21 41 45 μA-40°C

VDD = 3.0V34 38 μA+25°C

27 30 μA+85°C

All Devices 104 115 μA-40°C

VDD = 5.0V

86 95 μA+25°C

67 75 μA+85°C

Extended Devices Only 68 100 μA +125°C

PIC18LF2X21/4X21 0.31 0.35 mA -40°C

VDD = 2.0V

FOSC = 1 MHz

(RC_RUN mode,

INTOSC source)

0.31 0.35 mA +25°C

0.31 0.35 mA +85°C

PIC18LF2X21/4X21 0.55 0.60 mA -40°C

VDD = 3.0V0.51 0.60 mA +25°C

0.47 0.60 mA +85°C

All Devices 1.0 1.3 mA -40°C

VDD = 5.0V

0.94 1.3 mA +25°C

0.88 1.2 mA +85°C

Extended Devices Only 0.88 1.2 mA +125°C

27.2 DC Characteristics: Power-Down and Supply Current

PIC18F2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321 (Industrial) (Continued)

PIC18LF2221/2321/4221/4321

(Industrial)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

PIC18F2221/2321/4221/4321

(Industrial, Extended)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Device Typ Max Units Conditions

Legend: Shading of rows is to assist in readability of the table.

Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured

with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that

add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).

2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin

loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have

an impact on the current consumption.

The test conditions for all IDD measurements in active operation mode are:

OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;

MCLR = VDD; WDT enabled/disabled as specified.

3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.

4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less

than the sum of both specifications.

5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.

PIC18F2221/2321/4221/4321 FAMILY

Supply Current (IDD)(2)

PIC18LF2X21/4X21 0.69 0.9 mA -40°C

VDD = 2.0V

FOSC = 4 MHz

(RC_RUN mode,

INTOSC source)

0.70 0.9 mA +25°C

0.71 0.9 mA +85°C

PIC18LF2X21/4X21 1.17 1.45 mA -40°C

VDD = 3.0V1.15 1.45 mA +25°C

1.14 1.45 mA +85°C

All Devices 2.24 2.9 mA -40°C

VDD = 5.0V

2.20 2.9 mA +25°C

2.16 2.8 mA +85°C

Extended Devices Only 2.18 2.8 mA +125°C

PIC18LF2X21/4X21 3 5 μA-40°C

VDD = 2.0V

FOSC = 31 kHz

(RC_IDLE mode,

INTRC source)

35μA+25°C

35.6μA+85°C

PIC18LF2X21/4X21 4 7 μA-40°C

VDD = 3.0V57μA+25°C

510μA+85°C

All Devices 10 12 μA-40°C

VDD = 5.0V

10 12 μA+25°C

10 16 μA+85°C

Extended Devices Only 17 50 μA +125°C

27.2 DC Characteristics: Power-Down and Supply Current

PIC18F2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321 (Industrial) (Continued)

PIC18LF2221/2321/4221/4321

(Industrial)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

PIC18F2221/2321/4221/4321

(Industrial, Extended)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Device Typ Max Units Conditions

Legend: Shading of rows is to assist in readability of the table.

Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured

with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that

add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).

2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin

loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have

an impact on the current consumption.

The test conditions for all IDD measurements in active operation mode are:

OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;

MCLR = VDD; WDT enabled/disabled as specified.

3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.

4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less

than the sum of both specifications.

5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.

PIC18F2221/2321/4221/4321 FAMILY

Supply Current (IDD)(2)

PIC18LF2X21/4X21 160 230 μA-40°C

VDD = 2.0V

FOSC = 1 MHz

(RC_IDLE mode,

INTOSC source)

170 230 μA+25°C

170 230 μA+85°C

PIC18LF2X21/4X21 220 330 μA-40°C

VDD = 3.0V240 330 μA+25°C

250 330 μA+85°C

All Devices 410 500 μA-40°C

VDD = 5.0V

420 500 μA+25°C

430 500 μA+85°C

Extended Devices Only 450 500 μA+125°C

PIC18LF2X21/4X21 310 440 μA-40°C

VDD = 2.0V

FOSC = 4 MHz

(RC_IDLE mode,

INTOSC source)

330 440 μA+25°C

340 440 μA+85°C

PIC18LF2X21/4X21 480 750 μA-40°C

VDD = 3.0V500 750 μA+25°C

520 750 μA+85°C

All Devices 0.91 1.3 mA -40°C

VDD = 5.0V

0.93 1.3 mA +25°C

0.96 1.3 mA +85°C

Extended Devices Only 0.98 1.3 mA +125°C

27.2 DC Characteristics: Power-Down and Supply Current

PIC18F2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321 (Industrial) (Continued)

PIC18LF2221/2321/4221/4321

(Industrial)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

PIC18F2221/2321/4221/4321

(Industrial, Extended)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Device Typ Max Units Conditions

Legend: Shading of rows is to assist in readability of the table.

Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured

with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that

add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).

2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin

loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have

an impact on the current consumption.

The test conditions for all IDD measurements in active operation mode are:

OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;

MCLR = VDD; WDT enabled/disabled as specified.

3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.

4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less

than the sum of both specifications.

5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.

PIC18F2221/2321/4221/4321 FAMILY

Supply Current (IDD)(2)

PIC18LF2X21/4X21 0.22 0.35 mA -40°C

VDD = 2.0V

FOSC = 1 MHz

(PRI_RUN mode,

EC oscillator)

0.22 0.35 mA +25°C

0.21 0.3 mA +85°C

PIC18LF2X21/4X21 0.51 0.55 mA -40°C

VDD = 3.0V0.45 0.50 mA +25°C

0.39 0.45 mA +85°C

All Devices 1.14 1.15 mA -40°C

VDD = 5.0V

0.99 1.1 mA +25°C

0.83 1.1 mA +85°C

Extended Devices Only 0.80 1.1 mA +125°C

PIC18LF2X21/4X21 610 870 μA-40°C

VDD = 2.0V

FOSC = 4 MHz

(PRI_RUN mode,

EC oscillator)

610 870 μA+25°C

610 870 μA+85°C

PIC18LF2X21/4X21 1.16 1.83 mA -40°C

VDD = 3.0V1.10 1.83 mA +25°C

1.07 1.83 mA +85°C

All Devices 2.35 2.85 mA -40°C

VDD = 5.0V

2.24 2.85 mA +25°C

2.14 2.85 mA +85°C

Extended Devices Only 2.14 2.85 mA +125°C

Extended Devices Only 9 15 mA +125°C VDD = 4.2V FOSC = 25 MHz

(PRI_RUN mode,

EC oscillator)

12 20 mA +125°C VDD = 5.0V

All Devices 16 19 mA -40°C

VDD = 4.2V

FOSC = 40 MHz

(PRI_RUN mode,

EC oscillator)

14 19 mA +25°C

14 19 mA +85°C

All Devices 17 22.7 mA -40°C

VDD = 5.0V17 22.7 mA +25°C

17 22.7 mA +85°C

27.2 DC Characteristics: Power-Down and Supply Current

PIC18F2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321 (Industrial) (Continued)

PIC18LF2221/2321/4221/4321

(Industrial)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

PIC18F2221/2321/4221/4321

(Industrial, Extended)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Device Typ Max Units Conditions

Legend: Shading of rows is to assist in readability of the table.

Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured

with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that

add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).

2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin

loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have

an impact on the current consumption.

The test conditions for all IDD measurements in active operation mode are:

OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;

MCLR = VDD; WDT enabled/disabled as specified.

3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.

4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less

than the sum of both specifications.

5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.

PIC18F2221/2321/4221/4321 FAMILY

Supply Current (IDD)(2)

All Devices 7 10 mA -40°C

VDD = 4.2V

FOSC = 4 MHz,

16 MHz internal

(PRI_RUN HS+PLL)

610mA +25°C

610mA +85°C

Extended Devices Only 6 10 mA +125°C

All Devices 10 12 mA -40°C

VDD = 5.0V

FOSC = 4 MHz,

16 MHz internal

(PRI_RUN HS+PLL)

912mA +25°C

912mA +85°C

Extended Devices Only 9 12 mA +125°C

All Devices 17 19 mA -40°C

VDD = 4.2V

FOSC = 10 MHz,

40 MHz internal

(PRI_RUN HS+PLL)

15 19 mA +25°C

15 19 mA +85°C

All Devices 18 23 mA -40°C

VDD = 5.0V

FOSC = 10 MHz,

40 MHz internal

(PRI_RUN HS+PLL)

18 23 mA +25°C

18 23 mA +85°C

27.2 DC Characteristics: Power-Down and Supply Current

PIC18F2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321 (Industrial) (Continued)

PIC18LF2221/2321/4221/4321

(Industrial)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

PIC18F2221/2321/4221/4321

(Industrial, Extended)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Device Typ Max Units Conditions

Legend: Shading of rows is to assist in readability of the table.

Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured

with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that

add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).

2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin

loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have

an impact on the current consumption.

The test conditions for all IDD measurements in active operation mode are:

OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;

MCLR = VDD; WDT enabled/disabled as specified.

3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.

4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less

than the sum of both specifications.

5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.

PIC18F2221/2321/4221/4321 FAMILY

Supply Current (IDD)(2)

PIC18LF2X21/4X21 51 75 μA-40°C

VDD = 2.0V

FOSC = 1 MHz

(PRI_IDLE mode,

EC oscillator)

54 75 μA+25°C

60 75 μA+85°C

PIC18LF2X21/4X21 83 123 μA-40°C

VDD = 3.0V88 123 μA+25°C

93 123 μA+85°C

All Devices 180 260 μA-40°C

VDD = 5.0V

180 260 μA+25°C

180 260 μA+85°C

Extended Devices Only 190 260 μA +125°C

PIC18LF2X21/4X21 210 290 μA-40°C

VDD = 2.0V

FOSC = 4 MHz

(PRI_IDLE mode,

EC oscillator)

220 290 μA+25°C

230 290 μA+85°C

PIC18LF2X21/4X21 350 480 μA-40°C

VDD = 3.0V360 480 μA+25°C

370 480 μA+85°C

All Devices 0.69 1 mA -40°C

VDD = 5.0V

0.70 1 mA +25°C

0.72 1 mA +85°C

Extended Devices Only 0.74 1 mA +125°C

Extended Devices Only 3.7 4.0 mA +125°C VDD = 4.2V FOSC = 25 MHz

(PRI_IDLE mode,

EC oscillator)

4.6 5.0 mA +125°C VDD = 5.0V

All Devices 6.0 7.3 mA -40°C

VDD = 4.2V

FOSC = 40 MHz

(PRI_IDLE mode,

EC oscillator)

6.2 7.3 mA +25°C

6.6 7.3 mA +85°C

All Devices 6.8 9.2 mA -40°C

VDD = 5.0V7.0 9.2 mA +25°C

7.1 9.2 mA +85°C

27.2 DC Characteristics: Power-Down and Supply Current

PIC18F2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321 (Industrial) (Continued)

PIC18LF2221/2321/4221/4321

(Industrial)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

PIC18F2221/2321/4221/4321

(Industrial, Extended)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Device Typ Max Units Conditions

Legend: Shading of rows is to assist in readability of the table.

Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured

with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that

add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).

2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin

loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have

an impact on the current consumption.

The test conditions for all IDD measurements in active operation mode are:

OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;

MCLR = VDD; WDT enabled/disabled as specified.

3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.

4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less

than the sum of both specifications.

5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.

PIC18F2221/2321/4221/4321 FAMILY

Supply Current (IDD)(2)

PIC18LF2X21/4X21 12 19 μA -40°C(5)

VDD = 2.0V

FOSC = 32 kHz

(SEC_RUN mode,

Timer1 as clock)(3)

—19μA-10°C

13 19 μA+25°C

13 19 μA+85°C

PIC18LF2X21/4X21 40 45 μA -40°C(5)

VDD = 3.0V

—45μA-10°C

33 45 μA+25°C

27 45 μA+85°C

All Devices 101 115 μA -40°C(5)

VDD = 5.0V

—110μA-10°C

83 110 μA+25°C

65 88 μA+85°C

PIC18LF2X21/4X21 2.5 5 μA -40°C(5)

VDD = 2.0V

FOSC = 32 kHz

(SEC_IDLE mode,

Timer1 as clock)(3)

—5μA-10°C

3.0 5 μA+25°C

3.5 8 μA+85°C

PIC18LF2X21/4X21 3.9 7 μA -40°C(5)

VDD = 3.0V

—7μA-10°C

4.5 7 μA+25°C

5.2 10.7 μA+85°C

All Devices 7.5 10 μA -40°C(5)

VDD = 5.0V

—10μA-10°C

8.0 10 μA+25°C

8.6 15 μA+85°C

27.2 DC Characteristics: Power-Down and Supply Current

PIC18F2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321 (Industrial) (Continued)

PIC18LF2221/2321/4221/4321

(Industrial)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

PIC18F2221/2321/4221/4321

(Industrial, Extended)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Device Typ Max Units Conditions

Legend: Shading of rows is to assist in readability of the table.

Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured

with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that

add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).

2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin

loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have

an impact on the current consumption.

The test conditions for all IDD measurements in active operation mode are:

OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;

MCLR = VDD; WDT enabled/disabled as specified.

3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.

4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less

than the sum of both specifications.

5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.

PIC18F2221/2321/4221/4321 FAMILY

Module Differential Currents (ΔIWDT, ΔIBOR, ΔILVD, ΔIOSCB, ΔIAD)

D022

(ΔIWDT)

Watchdog Timer 1.6 2.5 μA-40°C

VDD = 2.0V1.6 2.5 μA+25°C

1.5 2.5 μA+85°C

2.3 3.5 μA-40°C

VDD = 3.0V2.2 3.5 μA+25°C

2.1 3 μA+85°C

3.4 7.4 μA-40°C

VDD = 5.0V

3.9 7.4 μA+25°C

4.4 7.4 μA+85°C

4.5 7.4 μA +125°C

D022A

(ΔIBOR)

Brown-out Reset(4) 34 45 μA -40°C to +85°C VDD = 3.0V

40 62.6 μA -40°C to +85°C VDD = 5.0V

42 62.6 μA -40°C to +125°C

02μA -40°C to +85°C VDD = 3.0V Sleep mode,

BOREN<1:0> = 10

05μA -40°C to +125°C VDD = 5.0V

D022B

(ΔILVD)

High/Low-Voltage

Detect(4)

23 35 μA -40°C to +85°C VDD = 2.0V

23 35 μA -40°C to +85°C VDD = 3.0V

28 35 μA -40°C to +85°C VDD = 5.0V

30 40 μA -40°C to +125°C

27.2 DC Characteristics: Power-Down and Supply Current

PIC18F2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321 (Industrial) (Continued)

PIC18LF2221/2321/4221/4321

(Industrial)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

PIC18F2221/2321/4221/4321

(Industrial, Extended)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Device Typ Max Units Conditions

Legend: Shading of rows is to assist in readability of the table.

Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured

with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that

add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).

2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin

loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have

an impact on the current consumption.

The test conditions for all IDD measurements in active operation mode are:

OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;

MCLR = VDD; WDT enabled/disabled as specified.

3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.

4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less

than the sum of both specifications.

5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.

PIC18F2221/2321/4221/4321 FAMILY

D025

(ΔIOSCB)

Timer1 Oscillator 2.1 4.5 μA -40°C(5)

VDD = 2.0V

32 kHz Tuning Fork,

Crystal on Timer1

Oscillator(3)

—4.5μA-10°C

1.8 4.5 μA+25°C

2.1 4.5 μA+85°C

2.2 6.0 μA -40°C(5)

VDD = 3.0V

—6μA-10°C

2.6 6.0 μA+25°C

2.9 6.0 μA+85°C

3.0 8.0 μA -40°C(5)

VDD = 5.0V

—8μA-10°C

3.2 8.0 μA+25°C

3.4 8.0 μA+85°C

D026

(ΔIAD)

A/D Converter 1.0 2.0 μA -40°C to +85°C VDD = 2.0V

A/D on, Not Converting

1.0 2.0 μA -40°C to +85°C VDD = 3.0V

1.0 2.0 μA -40°C to +85°C VDD = 5.0V

2.0 8.0 μA -40°C to +125°C

27.2 DC Characteristics: Power-Down and Supply Current

PIC18F2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321 (Industrial) (Continued)

PIC18LF2221/2321/4221/4321

(Industrial)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

PIC18F2221/2321/4221/4321

(Industrial, Extended)

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Device Typ Max Units Conditions

Legend: Shading of rows is to assist in readability of the table.

Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured

with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS, and all features that

add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).

2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin

loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have

an impact on the current consumption.

The test conditions for all IDD measurements in active operation mode are:

OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS;

MCLR = VDD; WDT enabled/disabled as specified.

3: Low-power, Timer1 oscillator is selected unless otherwise indicated, where LPT1OSC (CONFIG3H<2>) = 1.

4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less

than the sum of both specifications.

5: When operation below -10°C is expected, use T1OSC High-Power mode, where LPT1OSC (CONFIG3H<2>) = 0.

PIC18F2221/2321/4221/4321 FAMILY

27.3 DC Characteristics: PIC18F2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321 (Industrial)

DC CHARACTERISTICS

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ TA ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Symbol Characteristic Min Max Units Conditions

VIL Input Low Voltage

I/O Ports:

D030 with TTL Buffer VSS 0.15 VDD VVDD < 4.5V

D030A — 0.8 V 4.5V ≤ VDD ≤ 5.5V

D031 with Schmitt Trigger Buffer VSS 0.2 VDD V

D031A RC3 and RC4 VSS 0.3 VDD VI

2C™ enabled

D031B VSS 0.8 V SMBus enabled

D032 MCLR VSS 0.2 VDD V

D033 OSC1 VSS 0.3 VDD V HS, HSPLL modes

D033A

D033B

D034

OSC1

T13CKI

VSS

0.2 VDD

0.3

RC, EC modes(1)

XT, LP modes

VIH Input High Voltage

I/O Ports:

D040 with TTL Buffer 0.25 VDD +

0.8V

VDD VVDD < 4.5V

D040A 2.0 VDD V4.5V ≤ VDD ≤ 5.5V

D041 with Schmitt Trigger Buffer 0.8 VDD VDD V

D041A RC3 and RC4 0.7 VDD VDD VI

2C™ enabled

D041B 2.1 VDD V SMBus enabled,

VSS ≥ 3V

D042 MCLR 0.8 VDD VDD V

D043 OSC1 0.7 VDD VDD V HS, HSPLL modes

D043A

D043B

D043C

D044

OSC1

T13CKI

0.8 VDD

0.9 VDD

1.6

VDD

EC mode

RC mode(1)

XT, LP modes

IIL Input Leakage Current(2,3)

D060 I/O Ports —

—

±200

±50

VDD < 5.5V,

VSS ≤ VPIN ≤ VDD,

Pin at High-Impedance

VDD < 3V,

VSS ≤ VPIN ≤ VDD,

Pin at High-Impedance

D061 MCLR —±1 μAVss ≤ VPIN ≤ VDD

D063 OSC1 — ±1 μAVss ≤ VPIN ≤ VDD

Note 1: In RC oscillator configuration, the OSC1/CLKI pin is a Schmitt Trigger input. It is not recommended that the

PIC® device be driven with an external clock while in RC mode.

2: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified

levels represent normal operating conditions. Higher leakage current may be measured at different input

voltages.

3: Negative current is defined as current sourced by the pin.

PIC18F2221/2321/4221/4321 FAMILY

IPU Weak Pull-up Current

D070 IPURB PORTB Weak Pull-up Current 50 400 μAVDD = 5V, VPIN = VSS

VOL Output Low Voltage

D080 I/O Ports — 0.6 V IOL = 8.5 mA, VDD = 4.5V,

-40°C to +85°C

D083 OSC2/CLKO

(RC, RCIO, EC, ECIO modes)

—0.6VI

OL = 1.6 mA, VDD = 4.5V,

-40°C to +85°C

VOH Output High Voltage(3)

D090 I/O Ports VDD – 0.7 — V IOH = -3.0 mA, VDD = 4.5V,

-40°C to +85°C

D092 OSC2/CLKO

(RC, RCIO, EC, ECIO modes)

VDD – 0.7 — V IOH = -1.3 mA, VDD = 4.5V,

-40°C to +85°C

Capacitive Loading Specs

on Output Pins

D100 COSC2 OSC2 Pin — 15 pF In XT, HS and LP modes

when external clock is used

to drive OSC1

D101 CIO All I/O Pins and OSC2

(in RC mode)

— 50 pF Maximum that allows the

AC Timing Specifications to

be met

D102 CBSCL, SDA — 400 pF Maximum bus capacitance

permitted by I2C™

Specification

27.3 DC Characteristics: PIC18F2221/2321/4221/4321 (Industrial)

PIC18LF2221/2321/4221/4321 (Industrial) (Continued)

DC CHARACTERISTICS

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ TA ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Symbol Characteristic Min Max Units Conditions

Note 1: In RC oscillator configuration, the OSC1/CLKI pin is a Schmitt Trigger input. It is not recommended that the

PIC® device be driven with an external clock while in RC mode.

2: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified

levels represent normal operating conditions. Higher leakage current may be measured at different input

voltages.

3: Negative current is defined as current sourced by the pin.

PIC18F2221/2321/4221/4321 FAMILY

TABLE 27-1: MEMORY PROGRAMMING REQUIREMENTS

DC CHARACTERISTICS

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ TA ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Sym Characteristic Min Typ† Max Units Conditions

Data EEPROM Memory

D120 EDByte Endurance 1M 10M — E/W -40°C to +85°C

D121 VDRW VDD for Read/Write VMIN — 5.5 V Using EECON to read/write,

VMIN = Minimum operating

voltage

D122 TDEW Erase/Write Cycle Time — 4 — ms

D123 TRETD Characteristic Retention 40 — — Year Provided no other

specifications are violated

D124 TREF Number of Total Erase/Write

Cycles before Refresh(1)

100K 1M — E/W -40°C to +85°C

D125 IDDP Supply Current during

Programming

—10—mA

Program Flash Memory

D130 EPCell Endurance 10K 100K — E/W -40°C to +85°C

D131 VPR VDD for Read VMIN —5.5VVMIN = Minimum operating

voltage

D132 VIE VDD for Block Erase 3.0 — 5.5 V Using ICSP™ port, 25°C

D132B VPEW VDD for Self-Timed Write VMIN —5.5VVMIN = Minimum operating

voltage

D133A TIW Self-Timed Write Cycle Time — 2 — ms

D134 TRETD Characteristic Retention 40 100 — Year Provided no other

specifications are violated

D135 IDDP Supply Current during

Programming

—10—mA

† Data in “Typ” column is at 5.0V, 25°C unless otherwise stated. These parameters are for design guidance

only and are not tested.

Note 1: Refer to Section 8.7 “Using the Data EEPROM” for a more detailed discussion on data EEPROM

endurance.

PIC18F2221/2321/4221/4321 FAMILY

TABLE 27-2: COMPARATOR SPECIFICATIONS

TABLE 27-3: VOLTAGE REFERENCE SPECIFICATIONS

Operating Conditions: 3.0V < VDD < 5.5V, -40°C < TA < +85°C for industrial (unless otherwise stated)

-40°C < TA < +125°C for extended (unless otherwise stated)

Param

No. Sym Characteristics Min Typ Max Units Comments

D300 VIOFF Input Offset Voltage — ±5.0 ±10 mV

D301 VICM Input Common Mode Voltage 0 — VDD – 1.5 V

D302 CMRR Common Mode Rejection Ratio 55 — — dB

D303 TRESP Response Time(1) — 150 400 ns PIC18FXXXX

D303A — 150 600 ns PIC18LFXXXX,

VDD = 2.0V

D304 TMC2OV Comparator Mode Change to

Output Valid

—— 10μs

Note 1: Response time measured with one comparator input at (VDD – 1.5)/2, while the other input transitions

from VSS to VDD.

Operating Conditions: 3.0V < VDD < 5.5V, -40°C < TA < +85°C for industrial (unless otherwise stated)

-40°C < TA < +125°C for extended (unless otherwise stated)

Param

No. Sym Characteristics Min Typ Max Units Comments

D310 VRES Resolution VDD/24 — VDD/32 LSb

D311 VRAA Absolute Accuracy — — 1/2 LSb

D312 VRUR Unit Resistor Value (R) — 2k — Ω

D310 TSET Settling Time(1) — — 10 μs

Note 1: Settling time measured while CVRR = 1 and CVR<3:0> transitions from ‘0000’ to ‘1111’.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-4: HIGH/LOW-VOLTAGE DETECT CHARACTERISTICS

TABLE 27-4: HIGH/LOW-VOLTAGE DETECT CHARACTERISTICS

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ TA ≤ +85°C for industrial

-40°C ≤ TA ≤ +125°C for extended

Param

No. Symbol Characteristic Min Typ Max Units Conditions

D420 HLVD Voltage on VDD

Transition High-to-Low

LVV = 0000 2.06 2.17 2.28 V

LVV = 0001 2.12 2.23 2.34 V

LVV = 0010 2.24 2.36 2.48 V

LVV = 0011 2.32 2.44 2.56 V

LVV = 0100 2.47 2.60 2.73 V

LVV = 0101 2.65 2.79 2.93 V

LVV = 0110 2.74 2.89 3.04 V

LVV = 0111 2.96 3.12 3.28 V

LVV = 1000 3.22 3.39 3.56 V

LVV = 1001 3.37 3.55 3.73 V

LVV = 1010 3.52 3.71 3.90 V

LVV = 1011 3.70 3.90 4.10 V

LVV = 1100 3.90 4.11 4.32 V

LVV = 1101 4.11 4.33 4.55 V

LVV = 1110 4.36 4.59 4.82 V

LVV = 1111 1.10 1.20 1.30 V HLVDIN Input/Internal

Reference Voltage

VLVD

HLVDIF(1)

VDD

(HLVDIF set by hardware)

(HLVDIF can be

cleared in software)

Note 1: VDIRMAG = 0.

PIC18F2221/2321/4221/4321 FAMILY

27.4 AC (Timing) Characteristics

27.4.1 TIMING PARAMETER SYMBOLOGY

The timing parameter symbols have been created

using one of the following formats:

1. TppS2ppS 3. TCC:ST (I2C specifications only)

2. TppS 4. Ts (I2C specifications only)

F Frequency T Time

Lowercase letters (pp) and their meanings:

cc CCP1 osc OSC1

ck CLKO rd RD

cs CS rw RD or WR

di SDI sc SCK

do SDO ss SS

dt Data in t0 T0CKI

io I/O port t1 T13CKI

mc MCLR wr WR

Uppercase letters and their meanings:

F Fall P Period

HHigh RRise

I Invalid (High-impedance) V Valid

L Low Z High-impedance

I2C only

AA output access High High

BUF Bus free Low Low

CC:ST (I2C specifications only)

HD Hold SU Setup

DAT DATA input hold STO Stop condition

STA Start condition

PIC18F2221/2321/4221/4321 FAMILY

27.4.2 TIMING CONDITIONS

The temperature and voltages specified in Table 27-5

apply to all timing specifications unless otherwise

noted. Figure 27-5 specifies the load conditions for the

timing specifications.

TABLE 27-5: TEMPERATURE AND VOLTAGE SPECIFICATIONS – AC

FIGURE 27-5: LOAD CONDITIONS FOR DEVICE TIMING SPECIFICATIONS

Note: Because of space limitations, the generic

terms “PIC18FXXXX” and “PIC18LFXXXX”

are used throughout this section to refer to

the PIC18F2221/2321/4221/4321 and

PIC18LF2221/2321/4221/4321 families of

devices specifically and only those devices.

AC CHARACTERISTICS

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ TA ≤ +85°C for industrial

-40°C ≤ TA ≤ +125°C for extended

Operating voltage VDD range as described in DC spec Section 27.1 and

Section 27.3.

LF parts operate for industrial temperatures only.

VDD/2

VSS

RL=464Ω

CL= 50 pF for all pins except OSC2/CLKO

and including D and E outputs as ports

Load Condition 1 Load Condition 2

PIC18F2221/2321/4221/4321 FAMILY

27.4.3 TIMING DIAGRAMS AND SPECIFICATIONS

FIGURE 27-6: EXTERNAL CLOCK TIMING (ALL MODES EXCEPT PLL)

TABLE 27-6: EXTERNAL CLOCK TIMING REQUIREMENTS

Param.

No. Symbol Characteristic Min Max Units Conditions

1A FOSC External CLKI Frequency(1) DC 1 MHz XT, RC Oscillator mode

DC 25 MHz HS Oscillator mode

DC 40 MHz EC Oscillator mode

4 10 MHz HS+PLL Oscillator mode

DC 50 kHz LP Oscillator mode

Oscillator Frequency(1) DC 4 MHz RC Oscillator mode

0.1 4 MHz XT Oscillator mode

4 25 MHz HS Oscillator mode

5 200 kHz LP Oscillator mode

OSC External CLKI Period(1) 1000 — ns XT, RC Oscillator mode

40 — ns HS Oscillator mode

25 — ns EC Oscillator mode

100 250 ns HS+PLL Oscillator mode

32 — μs LP Oscillator mode

Oscillator Period(1) 250 — ns RC Oscillator mode

250 1 μs XT Oscillator mode

40 250 ns HS Oscillator mode

5209μs LP Oscillator mode

CY Instruction Cycle Time(1) 100 — ns TCY = 4/FOSC, Industrial

160 — ns T

CY = 4/FOSC, Extended

OSL,

OSH

External Clock in (OSC1)

High or Low Time

30 — ns XT Oscillator mode

2.5 — μs LP Oscillator mode

10 — ns HS Oscillator mode

OSR,

OSF

External Clock in (OSC1)

Rise or Fall Time

— 20 ns XT Oscillator mode

— 50 ns LP Oscillator mode

— 7.5 ns HS Oscillator mode

Note 1: Instruction cycle period (TCY) equals four times the input oscillator time base period for all configurations

except PLL. All specified values are based on characterization data for that particular oscillator type under

standard operating conditions with the device executing code. Exceeding these specified limits may result

in an unstable oscillator operation and/or higher than expected current consumption. All devices are tested

to operate at “min.” values with an external clock applied to the OSC1/CLKI pin. When an external clock

input is used, the “max.” cycle time limit is “DC” (no clock) for all devices.

OSC1

CLKO

Q4 Q1 Q2 Q3 Q4 Q1

3344

PIC18F2221/2321/4221/4321 FAMILY

TABLE 27-7: PLL CLOCK TIMING SPECIFICATIONS (VDD = 4.2V TO 5.5V)

TABLE 27-8: AC CHARACTERISTICS: INTERNAL RC ACCURACY

Param

No. Sym Characteristic Min Typ† Max Units Conditions

F10 FOSC Oscillator Frequency Range 4 — 10 MHz HS mode only

F11 FSYS On-Chip VCO System Frequency 16 — 40 MHz HS mode only

F12 trc PLL Start-up Time (Lock Time) — — 2 ms

F13 ΔCLK CLKO Stability (Jitter) -2 — +2 %

† Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance

only and are not tested.

Standard Operating Conditions (unless otherwise stated)

Operating temperature -40°C ≤ T

A ≤ +85°C for industrial

-40°C ≤ T

A ≤ +125°C for extended

Param

No. Device Min Typ Max Units Conditions

INTOSC Accuracy @ Freq = 8 MHz, 4 MHz, 2 MHz, 1 MHz, 500 kHz, 250 kHz, 125 kHz, 31 kHz(1)

PIC18LF2221/2321/4221/4321 -2 +/-1 2 % +25°C VDD = 2.0-5.5V

-5 — 5 % -10°C to +85°C VDD = 2.0-5.5V

-10 +/-1 10 % -40°C to +85°C VDD = 2.0-5.5V

PIC18F2221/2321/4221/4321 -2 +/-1 2 % +25°C VDD = 4.2-5.5V

-5 — 5 % -10°C to +85°C VDD = 4.2-5.5V

-10 +/-1 10 % -40°C to +85°C VDD = 4.2-5.5V

INTRC Accuracy @ Freq = 31 kHz

PIC18LF2221/2321/4221/4321 26.562 — 35.938 kHz -40°C to +85°C VDD = 2.0-5.5V

PIC18F2221/2321/4221/4321 26.562 — 35.938 kHz -40°C to +85°C VDD = 4.2-5.5V

Note 1: Frequency calibrated at 25°C. OSCTUNE register can be used to compensate for temperature drift.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-7: CLKO AND I/O TIMING

TABLE 27-9: CLKO AND I/O TIMING REQUIREMENTS

Param

No. Symbol Characteristic Min Typ Max Units Conditions

10 TosH2ckL OSC1 ↑ to CLKO ↓ — 75 200 ns (Note 1)

11 TosH2ckH OSC1 ↑ to CLKO ↑ — 75 200 ns (Note 1)

12 TckR CLKO Rise Time — 35 100 ns (Note 1)

13 TckF CLKO Fall Time — 35 100 ns (Note 1)

14 TckL2ioV CLKO ↓ to Port Out Valid — — 0.5 T

CY + 20 ns (Note 1)

15 TioV2ckH Port In Valid before CLKO ↑ 0.25 T

CY + 25 — — ns (Note 1)

16 TckH2ioI Port In Hold after CLKO ↑ 0——ns(Note 1)

17 TosH2ioV OSC1 ↑ (Q1 cycle) to Port Out Valid — 50 150 ns

18 TosH2ioI OSC1 ↑ (Q2 cycle) to

Port Input Invalid

(I/O in hold time)

PIC18FXXXX 100 — — ns

18A PIC18LFXXXX 200 — — ns VDD = 2.0V

19 TioV2osH Port Input Valid to OSC1 ↑ (I/O in setup time) 0 — — ns

20 TioR Port Output Rise Time PIC18FXXXX — 10 25 ns

20A PIC18LFXXXX — — 60 ns VDD = 2.0V

21 TioF Port Output Fall Time PIC18FXXXX — 10 25 ns

21A PIC18LFXXXX — — 60 ns VDD = 2.0V

22† TINP INTx Pin High or Low Time TCY ——ns

23† TRBP RB<7:4> Change INTx High or Low Time TCY ——ns

† These parameters are asynchronous events not related to any internal clock edges.

Note 1: Measurements are taken in RC mode, where CLKO output is 4 x TOSC.

Note: Refer to Figure 27-5 for load conditions.

OSC1

CLKO

I/O pin

(Input)

I/O pin

(Output)

Q4 Q1 Q2 Q3

20, 21

19 18

Old Value New Value

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-8: RESET, WATCHDOG TIMER, OSCILLATOR START-UP TIMER AND

POWER-UP TIMER TIMING

FIGURE 27-9: BROWN-OUT RESET TIMING

TABLE 27-10: RESET, WATCHDOG TIMER, OSCILLATOR START-UP TIMER, POWER-UP TIMER

AND BROWN-OUT RESET REQUIREMENTS

Param.

No. Symbol Characteristic Min Typ Max Units Conditions

30 TmcL MCLR Pulse Width (low) 2 — — μs

31 TWDT Watchdog Timer Time-out Period

(no postscaler)

3.56 4.19 4.82 ms

32 TOST Oscillation Start-up Timer Period 1024 TOSC — 1024 TOSC —TOSC = OSC1 period

33 TPWRT Power-up Timer Period 57 67 77 ms

34 TIOZ I/O High-Impedance from MCLR

Low or Watchdog Timer Reset

—2—μs

35 TBOR Brown-out Reset Pulse Width 200 — — μsVDD ≤ BVDD (see D005)

36 TIRVST Time for Internal Reference

Voltage to become Stable

—2050 μs

37 TLVD High/Low-Voltage Detect Pulse Width 200 — — μsVDD ≤ VLVD

38 TCSD CPU Start-up Time — 10 — μs

39 TIOBST Time for INTOSC to Stabilize — 1 — μs

VDD

MCLR

Internal

POR

PWRT

Time-out

OSC

Time-out

Internal

Reset

Watchdog

Timer

Reset

I/O pins

VDD BVDD

VIRVST

Enable Internal

Internal Reference 36

Reference Voltage

Voltage Stable

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-10: TIMER0 AND TIMER1 EXTERNAL CLOCK TIMINGS

TABLE 27-11: TIMER0 AND TIMER1 EXTERNAL CLOCK REQUIREMENTS

Param

No. Symbol Characteristic Min Max Units Conditions

40 Tt0H T0CKI High Pulse Width No prescaler 0.5 T

CY + 20 — ns

With prescaler 10 — ns

41 Tt0L T0CKI Low Pulse Width No prescaler 0.5 TCY + 20 — ns

With prescaler 10 — ns

42 Tt0P T0CKI Period No prescaler TCY + 10 — ns

With prescaler Greater of:

20 ns or

(TCY + 40)/N

— ns N = prescale

value

(1, 2, 4,..., 256)

45 Tt1H T13CKI

High Time

Synchronous, no prescaler 0.5 TCY + 20 — ns

Synchronous,

with prescaler

PIC18FXXXX 10 — ns

PIC18LFXXXX 25 — ns VDD = 2.0V

Asynchronous PIC18FXXXX 30 — ns

PIC18LFXXXX 50 — ns VDD = 2.0V

46 Tt1L T13CKI

Low Time

Synchronous, no prescaler 0.5 TCY + 5 — ns

Synchronous,

with prescaler

PIC18FXXXX 10 — ns

PIC18LFXXXX 25 — ns VDD = 2.0V

Asynchronous PIC18FXXXX 30 — ns

PIC18LFXXXX 50 — ns VDD = 2.0V

47 Tt1P T13CKI

Input

Period

Synchronous Greater of:

20 ns or

(TCY + 40)/N

— ns N = prescale

value (1, 2, 4, 8)

Asynchronous 60 — ns

Ft1 T13CKI Oscillator Input Frequency Range DC 50 kHz

48 Tcke2tmrI Delay from External T13CKI Clock Edge to

Timer Increment

2 T

OSC 7 TOSC —

T0CKI

T1OSO/T13CKI

TMR0 or

TMR1

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-11: CAPTURE/COMPARE/PWM TIMINGS (ALL CCP MODULES)

TABLE 27-12: CAPTURE/COMPARE/PWM REQUIREMENTS (ALL CCP MODULES)

Param

No. Symbol Characteristic Min Max Units Conditions

50 TccL CCPx Input Low

Time

No prescaler 0.5 TCY + 20 — ns

With

prescaler

PIC18FXXXX 10 — ns

PIC18LFXXXX 20 — ns VDD = 2.0V

51 TccH CCPx Input

High Time

No prescaler 0.5 TCY + 20 — ns

With

prescaler

PIC18FXXXX 10 — ns

PIC18LFXXXX 20 — ns VDD = 2.0V

52 TccP CCPx Input Period 3 TCY + 40

— ns N = prescale

value (1, 4 or 16)

53 TccR CCPx Output Fall Time PIC18FXXXX — 25 ns

PIC18LFXXXX — 45 ns VDD = 2.0V

54 TccF CCPx Output Fall Time PIC18FXXXX — 25 ns

PIC18LFXXXX — 45 ns VDD = 2.0V

CCPx

(Capture Mode)

50 51

CCPx

53 54

(Compare or PWM Mode)

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-12: PARALLEL SLAVE PORT TIMING (PIC18F4221/4321)

TABLE 27-13: PARALLEL SLAVE PORT REQUIREMENTS (PIC18F4221/4321)

Param.

No. Symbol Characteristic Min Max Units Conditions

62 TdtV2wrH Data In Valid before WR ↑ or CS ↑ (setup time) 20 — ns

63 TwrH2dtI WR ↑ or CS ↑ to Data–In

Invalid (hold time)

PIC18FXXXX 20 — ns

PIC18LFXXXX 35 — ns VDD = 2.0V

64 TrdL2dtV RD ↓ and CS ↓ to Data–Out Valid — 80 ns

65 TrdH2dtI RD ↑ or CS ↓ to Data–Out Invalid 10 30 ns

66 TibfINH Inhibit of the IBF Flag bit being Cleared from

WR ↑ or CS ↑

—3 T

Note: Refer to Figure 27-5 for load conditions.

RE2/CS

RE0/RD

RE1/WR

RD<7:0>

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-13: EXAMPLE SPI MASTER MODE TIMING (CKE = 0)

TABLE 27-14: EXAMPLE SPI MODE REQUIREMENTS (MASTER MODE, CKE = 0)

Param

No. Symbol Characteristic Min Max Units Conditions

73 TdiV2scH,

TdiV2scL

Setup Time of SDI Data Input to SCK Edge 20 — ns

73A Tb2b Last Clock Edge of Byte 1 to the 1st Clock Edge

of Byte 2

1.5 TCY + 40 — ns

74 TscH2diL,

TscL2diL

Hold Time of SDI Data Input to SCK Edge 40 — ns

75 TdoR SDO Data Output Rise Time PIC18FXXXX — 25 ns

PIC18LFXXXX — 45 ns VDD = 2.0V

76 TdoF SDO Data Output Fall Time — 25 ns

78 TscR SCK Output Rise Time PIC18FXXXX — 25 ns

PIC18LFXXXX — 45 ns VDD = 2.0V

79 TscF SCK Output Fall Time — 25 ns

80 TscH2doV,

TscL2doV

SDO Data Output Valid after

SCK Edge

PIC18FXXXX — 50 ns

PIC18LFXXXX — 100 ns VDD = 2.0V

SCK

(CKP = 0)

SCK

(CKP = 1)

SDO

SDI

75, 76

MSb LSb

bit 6 - - - - - -1

MSb In LSb In

bit 6 - - - -1

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-14: EXAMPLE SPI MASTER MODE TIMING (CKE = 1)

TABLE 27-15: EXAMPLE SPI MODE REQUIREMENTS (MASTER MODE, CKE = 1)

Param.

No. Symbol Characteristic Min Max Units Conditions

73 TdiV2scH,

TdiV2scL

Setup Time of SDI Data Input to SCK Edge 20 — ns

73A Tb2b Last Clock Edge of Byte 1 to the 1st Clock Edge

of Byte 2

1.5 TCY + 40 — ns

74 TscH2diL,

Ts c L 2 d i L

Hold Time of SDI Data Input to SCK Edge 40 — ns

75 TdoR SDO Data Output Rise Time PIC18FXXXX — 25 ns

PIC18LFXXXX 45 ns VDD = 2.0V

76 TdoF SDO Data Output Fall Time — 25 ns

78 TscR SCK Output Rise Time PIC18FXXXX — 25 ns

PIC18LFXXXX 45 ns VDD = 2.0V

79 TscF SCK Output Fall Time — 25 ns

80 TscH2doV,

TscL2doV

SDO Data Output Valid after

SCK Edge

PIC18FXXXX — 50 ns

PIC18LFXXXX 100 ns VDD = 2.0V

81 TdoV2scH,

TdoV2scL

SDO Data Output Setup to SCK Edge TCY —ns

SCK

(CKP = 0)

SCK

(CKP = 1)

SDO

SDI

75, 76

MSb

MSb In

bit 6 - - - - - -1

LSb In

bit 6 - - - -1

LSb

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-15: EXAMPLE SPI SLAVE MODE TIMING (CKE = 0)

TABLE 27-16: EXAMPLE SPI MODE REQUIREMENTS (SLAVE MODE TIMING, CKE = 0)

Param

No. Symbol Characteristic Min Max Units Conditions

70 TssL2scH,

Ts s L 2s c L

SS ↓ to SCK ↓ or SCK ↑ Input 3 TCY —ns

71 TscH SCK Input High Time Continuous 1.25 TCY + 30 — ns

71A Single Byte 40 — ns (Note 1)

72 TscL SCK Input Low Time Continuous 1.25 TCY + 30 — ns

72A Single Byte 40 — ns (Note 1)

73 TdiV2scH,

TdiV2scL

Setup Time of SDI Data Input to SCK Edge 20 — ns

73A Tb2b Last Clock Edge of Byte 1 to the First Clock Edge of Byte 2 1.5 TCY + 40 — ns (Note 2)

74 TscH2diL,

Ts c L 2 d iL

Hold Time of SDI Data Input to SCK Edge 40 — ns

75 TdoR SDO Data Output Rise Time PIC18FXXXX — 25 ns

PIC18LFXXXX 45 ns VDD = 2.0V

76 TdoF SDO Data Output Fall Time — 25 ns

77 TssH2doZ SS ↑ to SDO Output High-Impedance 10 50 ns

80 TscH2doV,

TscL2doV

SDO Data Output Valid after SCK Edge PIC18FXXXX — 50 ns

PIC18LFXXXX 100 ns VDD = 2.0V

83 TscH2ssH,

Ts c L 2s s H

SS ↑ after SCK edge 1.5 TCY + 40 — ns

Note 1: Requires the use of Parameter #73A.

2: Only if Parameter #71A and #72A are used.

SCK

(CKP = 0)

SCK

(CKP = 1)

SDO

SDI

71 72

73 74

75, 76 77

MSb LSb

bit 6 - - - - - -1

bit 6 - - - -1 LSb In

MSb In

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-16: EXAMPLE SPI SLAVE MODE TIMING (CKE = 1)

TABLE 27-17: EXAMPLE SPI SLAVE MODE REQUIREMENTS (CKE = 1)

Param

No. Symbol Characteristic Min Max Units Conditions

70 TssL2scH,

TssL2scL

SS ↓ to SCK ↓ or SCK ↑ Input 3 TCY —ns

71 TscH SCK Input High Time Continuous 1.25 TCY + 30 — ns

71A Single Byte 40 — ns (Note 1)

72 TscL SCK Input Low Time Continuous 1.25 TCY + 30 — ns

72A Single Byte 40 — ns (Note 1)

73A Tb2b Last Clock Edge of Byte 1 to the First Clock Edge of Byte 2 1.5 TCY + 40 — ns (Note 2)

74 TscH2diL,

TscL2diL

Hold Time of SDI Data Input to SCK Edge 40 — ns

75 TdoR SDO Data Output Rise Time PIC18FXXXX — 25 ns

PIC18LFXXXX 45 ns VDD = 2.0V

76 TdoF SDO Data Output Fall Time — 25 ns

77 TssH2doZ SS ↑ to SDO Output High-Impedance 10 50 ns

80 TscH2doV,

TscL2doV

SDO Data Output Valid after SCK

Edge

PIC18FXXXX — 50 ns

PIC18LFXXXX — 100 ns VDD = 2.0V

82 TssL2doV SDO Data Output Valid after SS ↓

Edge

PIC18FXXXX — 50 ns

PIC18LFXXXX — 100 ns VDD = 2.0V

83 TscH2ssH,

TscL2ssH

SS ↑ after SCK Edge 1.5 TCY + 40 — ns

Note 1: Requires the use of Parameter #73A.

2: Only if Parameter #71A and #72A are used.

SCK

(CKP = 0)

SCK

(CKP = 1)

SDO

SDI

71 72

SDI

75, 76

MSb bit 6 - - - - - -1 LSb

MSb In bit 6 - - - -1 LSb In

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-17: I2C™ BUS START/STOP BITS TIMING

TABLE 27-18: I2C™ BUS START/STOP BITS REQUIREMENTS (SLAVE MODE)

FIGURE 27-18: I2C™ BUS DATA TIMING

Param.

No. Symbol Characteristic Min Max Units Conditions

90 TSU:STA Start Condition 100 kHz mode 4700 — ns Only relevant for Repeated

Start condition

Setup Time 400 kHz mode 600 —

91 THD:STA Start Condition 100 kHz mode 4000 — ns After this period, the first

clock pulse is generated

Hold Time 400 kHz mode 600 —

92 TSU:STO Stop Condition 100 kHz mode 4700 — ns

Setup Time 400 kHz mode 600 —

93 THD:STO Stop Condition 100 kHz mode 4000 — ns

Hold Time 400 kHz mode 600 —

SCL

SDA

Start

Condition

Stop

Condition

91 92

100

101

103

106 107

109 109

110

102

SCL

SDA

Out

PIC18F2221/2321/4221/4321 FAMILY

TABLE 27-19: I2C™ BUS DATA REQUIREMENTS (SLAVE MODE)

Param.

No. Symbol Characteristic Min Max Units Conditions

100 THIGH Clock High Time 100 kHz mode 4.0 — μs

400 kHz mode 0.6 — μs

MSSP Module 1.5 TCY —

101 TLOW Clock Low Time 100 kHz mode 4.7 — μs

400 kHz mode 1.3 — μs

MSSP Module 1.5 TCY —

102 TRSDA and SCL Rise

Time

100 kHz mode — 1000 ns

400 kHz mode 20 + 0.1 CB300 ns CB is specified to be from

10 to 400 pF

103 TFSDA and SCL Fall

Time

100 kHz mode — 300 ns

400 kHz mode 20 + 0.1 CB300 ns CB is specified to be from

10 to 400 pF

90 TSU:STA Start Condition

Setup Time

100 kHz mode 4.7 — μs Only relevant for Repeated

Start condition

400 kHz mode 0.6 — μs

91 THD:STA Start Condition

Hold Time

100 kHz mode 4.0 — μs After this period, the first

clock pulse is generated

400 kHz mode 0.6 — μs

106 THD:DAT Data Input Hold

Time

100 kHz mode 0 — ns

400 kHz mode 0 0.9 μs

107 TSU:DAT Data Input Setup

Time

100 kHz mode 250 — ns (Note 2)

400 kHz mode 100 — ns

92 TSU:STO Stop Condition

Setup Time

100 kHz mode 4.7 — μs

400 kHz mode 0.6 — μs

109 TAA Output Valid from

Clock

100 kHz mode — 3500 ns (Note 1)

400 kHz mode — — ns

110 TBUF Bus Free Time 100 kHz mode 4.7 — μs Time the bus must be free

before a new transmission

can start

400 kHz mode 1.3 — μs

D102 CBBus Capacitive Loading — 400 pF

Note 1: As a transmitter, the device must provide this internal minimum delay time to bridge the undefined region

(min. 300 ns) of the falling edge of SCL to avoid unintended generation of Start or Stop conditions.

2: A Fast mode I2C bus device can be used in a Standard mode I2C bus system, but the requirement

SU:DAT ≥250 ns must then be met. This will automatically be the case if the device does not stretch the

LOW period of the SCL signal. If such a device does stretch the LOW period of the SCL signal, it must

output the next data bit to the SDA line, TR max. + TSU:DAT = 1000 + 250 = 1250 ns (according to the

Standard mode I2C bus specification), before the SCL line is released.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-19: MASTER SSP I2C™ BUS START/STOP BITS TIMING WAVEFORMS

TABLE 27-20: MASTER SSP I2C™ BUS START/STOP BITS REQUIREMENTS

FIGURE 27-20: MASTER SSP I2C™ BUS DATA TIMING

Param.

No. Symbol Characteristic Min Max Units Conditions

90 TSU:STA Start Condition 100 kHz mode 2(TOSC)(BRG + 1) — ns Only relevant for

Repeated Start

condition

Setup Time 400 kHz mode 2(TOSC)(BRG + 1) —

1 MHz mode(1) 2(TOSC)(BRG + 1) —

91 THD:STA Start Condition 100 kHz mode 2(TOSC)(BRG + 1) — ns After this period, the

first clock pulse is

generated

Hold Time 400 kHz mode 2(TOSC)(BRG + 1) —

1 MHz mode(1) 2(TOSC)(BRG + 1) —

92 TSU:STO Stop Condition 100 kHz mode 2(TOSC)(BRG + 1) — ns

Setup Time 400 kHz mode 2(TOSC)(BRG + 1) —

1 MHz mode(1) 2(TOSC)(BRG + 1) —

93 THD:STO Stop Condition 100 kHz mode 2(TOSC)(BRG + 1) — ns

Hold Time 400 kHz mode 2(TOSC)(BRG + 1) —

1 MHz mode(1) 2(TOSC)(BRG + 1) —

Note 1: Maximum pin capacitance = 10 pF for all I2C pins.

91 93

SCL

SDA

Start

Condition

Stop

Condition

90 92

90 91 92

100

101

103

106 107

109 109 110

102

SCL

SDA

Out

PIC18F2221/2321/4221/4321 FAMILY

TABLE 27-21: MASTER SSP I2C™ BUS DATA REQUIREMENTS

Param.

No. Symbol Characteristic Min Max Units Conditions

100 THIGH Clock High Time 100 kHz mode 2(TOSC)(BRG + 1) — ms

400 kHz mode 2(TOSC)(BRG + 1) — ms

1 MHz mode(1) 2(TOSC)(BRG + 1) — ms

101 TLOW Clock Low Time 100 kHz mode 2(TOSC)(BRG + 1) — ms

400 kHz mode 2(TOSC)(BRG + 1) — ms

1 MHz mode(1) 2(TOSC)(BRG + 1) — ms

102 TRSDA and SCL

Rise Time

100 kHz mode — 1000 ns CB is specified to be from

10 to 400 pF

400 kHz mode 20 + 0.1 CB300 ns

1 MHz mode(1) — 300 ns

103 TFSDA and SCL

Fall Time

100 kHz mode — 300 ns CB is specified to be from

10 to 400 pF

400 kHz mode 20 + 0.1 CB 300 ns

1 MHz mode(1) — 100 ns

90 T

SU:STA Start Condition

Setup Time

100 kHz mode 2(TOSC)(BRG + 1) — ms Only relevant for

Repeated Start

condition

400 kHz mode 2(TOSC)(BRG + 1) — ms

1 MHz mode(1) 2(TOSC)(BRG + 1) — ms

91 THD:STA Start Condition

Hold Time

100 kHz mode 2(TOSC)(BRG + 1) — ms After this period, the first

clock pulse is generated

400 kHz mode 2(TOSC)(BRG + 1) — ms

1 MHz mode(1) 2(TOSC)(BRG + 1) — ms

106 THD:DAT Data Input

Hold Time

100 kHz mode 0 — ns

400 kHz mode 0 0.9 ms

107 T

SU:DAT Data Input

Setup Time

100 kHz mode 250 — ns (Note 2)

400 kHz mode 100 — ns

92 TSU:STO Stop Condition

Setup Time

100 kHz mode 2(TOSC)(BRG + 1) — ms

400 kHz mode 2(TOSC)(BRG + 1) — ms

1 MHz mode(1) 2(TOSC)(BRG + 1) — ms

109 TAA Output Valid

from Clock

100 kHz mode — 3500 ns

400 kHz mode — 1000 ns

1 MHz mode(1) ——ns

110 TBUF Bus Free Time 100 kHz mode 4.7 — ms Time the bus must be free

before a new transmission

can start

400 kHz mode 1.3 — ms

D102 CBBus Capacitive Loading — 400 pF

Note 1: Maximum pin capacitance = 10 pF for all I2C pins.

2: A Fast mode I2C bus device can be used in a Standard mode I2C bus system, but parameter 107 ≥250 ns

must then be met. This will automatically be the case if the device does not stretch the LOW period of the

SCL signal. If such a device does stretch the LOW period of the SCL signal, it must output the next data bit

to the SDA line, parameter 102 + parameter 107 = 1000 + 250 = 1250 ns (for 100 kHz mode), before the

SCL line is released.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-21: EUSART SYNCHRONOUS TRANSMISSION (MASTER/SLAVE) TIMING

TABLE 27-22: EUSART SYNCHRONOUS TRANSMISSION REQUIREMENTS

FIGURE 27-22: EUSART SYNCHRONOUS RECEIVE (MASTER/SLAVE) TIMING

TABLE 27-23: EUSART SYNCHRONOUS RECEIVE REQUIREMENTS

Param

No. Symbol Characteristic Min Max Units Conditions

120 TckH2dtV SYNC XMIT (MASTER & SLAVE)

Clock High to Data Out Valid PIC18FXXXX — 40 ns

PIC18LFXXXX — 100 ns VDD = 2.0V

121 Tckrf Clock Out Rise Time and Fall Time

(Master mode)

PIC18FXXXX — 20 ns

PIC18LFXXXX — 50 ns VDD = 2.0V

122 Tdtrf Data Out Rise Time and Fall Time PIC18FXXXX — 20 ns

PIC18LFXXXX — 50 ns VDD = 2.0V

Param.

No. Symbol Characteristic Min Max Units Conditions

125 TdtV2ckl SYNC RCV (MASTER & SLAVE)

Data Hold before CK ↓ (DT hold time) 10 — ns

126 TckL2dtl Data Hold after CK ↓ (DT hold time) 15 — ns

121 121

120 122

RC6/TX/CK

RC7/RX/DT

125

126

RC6/TX/CK

RC7/RX/DT

PIC18F2221/2321/4221/4321 FAMILY

TABLE 27-24: A/D CONVERTER CHARACTERISTICS

Param

No. Symbol Characteristic Min Typ Max Units Conditions

A01 NRResolution — — 10 bit ΔVREF ≥ 3.0V

A03 EIL Integral Linearity Error — — <±1 LSb ΔVREF ≥ 3.0V

A04 EDL Differential Linearity Error — — <±1 LSb ΔVREF ≥ 3.0V

A06 EOFF Offset Error — — <±2 LSb ΔVREF ≥ 3.0V

A07 EGN Gain Error — — <±1 LSb ΔVREF ≥ 3.0V

A10 — Monotonicity Guaranteed(1) —VSS ≤ VAIN ≤ VREF

A20 ΔVREF Reference Voltage Range

(VREFH – VREFL)

1.8

—

VDD < 3.0V

VDD ≥ 3.0V

A21 VREFH Reference Voltage High — — VDD + 3.0V V

A22 VREFL Reference Voltage Low VSS – 0.3V — — V

A25 VAIN Analog Input Voltage VREFL —VREFH V

A30 ZAIN Recommended Impedance of

Analog Voltage Source

——2.5kΩ

A50 IREF VREF Input Current(2) —

—

150

μA

During VAIN acquisition.

During A/D conversion

cycle.

Note 1: The A/D conversion result never decreases with an increase in the input voltage and has no missing codes.

2: VREFH current is from RA3/AN3/VREF+ pin or VDD, whichever is selected as the VREFH source.

VREFL current is from RA2/AN2/VREF-/CVREF pin or VSS, whichever is selected as the VREFL source.

PIC18F2221/2321/4221/4321 FAMILY

FIGURE 27-23: A/D CONVERSION TIMING

TABLE 27-25: A/D CONVERSION REQUIREMENTS

Param

No. Symbol Characteristic Min Max Units Conditions

130 TAD A/D Clock Period PIC18FXXXX 0.7 25.0(1) μsTOSC based, VREF ≥ 3.0V

PIC18LFXXXX 1.4 25.0(1) μsVDD = 2.0V;

OSC based, VREF full range

PIC18FXXXX — 1 μs A/D RC mode

PIC18LFXXXX — 3 μsV

DD = 2.0V; A/D RC mode

131 TCNV Conversion Time

(not including acquisition time)(2)

11 12 TAD

132 TACQ Acquisition Time(3) 1.4 — μs-40°C to +85°C

135 TSWC Switching Time from Convert → Sample — (Note 4)

137 TDIS Discharge Time 0.2 — μs

Note 1: The time of the A/D clock period is dependent on the device frequency and the TAD clock divider.

2: ADRES register may be read on the following TCY cycle.

3: The time for the holding capacitor to acquire the “New” input voltage when the voltage changes full scale

after the conversion (VDD to VSS or VSS to VDD). The source impedance (RS) on the input channels is 50Ω.

4: On the following cycle of the device clock.

131

130

132

BSF ADCON0, GO

A/D CLK(1)

A/D DATA

ADRES

ADIF

SAMPLE

OLD_DATA

SAMPLING STOPPED

DONE

NEW_DATA

(Note 2)

987 21 0

Note 1: If the A/D clock source is selected as RC, a time of TCY is added before the A/D clock starts.

This allows the SLEEP instruction to be executed.

2: This is a minimal RC delay (typically 100 ns), which also disconnects the holding capacitor from the analog input.

. . . . . .

TCY

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

28.0 PACKAGING INFORMATION

28.1 Package Marking Information

28-Lead SPDIP

XXXXXXXXXXXXXXXXX

YYWWNNN

Example

PIC18F2321-I/SP

0910017

28-Lead SOIC

XXXXXXXXXXXXXXXXXXXX

YYWWNNN

Example

PIC18F2321-E/SO

0910017

Legend: XX...X Customer-specific information

Y Year code (last digit of calendar year)

YY Year code (last 2 digits of calendar year)

WW Week code (week of January 1 is week ‘01’)

NNN Alphanumeric traceability code

Pb-free JEDEC designator for Matte Tin (Sn)

*This package is Pb-free. The Pb-free JEDEC designator ( )

can be found on the outer packaging for this package.

Note: In the event the full Microchip part number cannot be marked on one line, it will

be carried over to the next line, thus limiting the number of available

characters for customer-specific information.

28-Lead QFN

XXXXXXXX

YYWWNNN

Example

18F2321

/ML

0910017

28-Lead SSOP

XXXXXXXXXXXX

YYWWNNN

Example

PIC18F2321

-I/SS

0910017

PIC18F2221/2321/4221/4321 FAMILY

28.1 Package Marking Information (Continued)

44-Lead TQFP

XXXXXXXXXX

YYWWNNN

Example

PIC18F4321

-I/PT

0910017

XXXXXXXXXX

44-Lead QFN

XXXXXXXXXX

YYWWNNN

PIC18F4321

Example

-I/ML

0910017

40-Lead PDIP

XXXXXXXXXXXXXXXXXX

YYWWNNN

Example

PIC18F4321-I/P

0910017

PIC18F2221/2321/4221/4321 FAMILY

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  !"#$%&"' ()"&'"!&)&#*&&&#

 +%&,&!&

- '!!#.#&"#'#%!&"!!#%!&"!!!&$#/!#

 '!#&.0

1,2 1!'!&$& "!**&"&&!

!" 3&'!&"&4#*!(!!&4%&&#&

&&255***''54

6&! 7,8.

'!9'&! 7 7: ;

7"')%! 7 <

&  1,

&&  = = 

##44!!   - 

1!&&   = =

"#&"#>#& .  - --

##4>#& .  < 

: 9&  - -? 

&& 9  - 

9#4!!  <  

69#>#& )   

9*9#>#& )  < 

: *+ 1 = = -

NOTE 1

  * ,1

PIC18F2221/2321/4221/4321 FAMILY

##$%&'(#)

!"

  !"#$%&"' ()"&'"!&)&#*&&&#

 +%&,&!&

- '!!#.#&"#'#%!&"!!#%!&"!!!&$#''!#

 '!#&.0

1,2 1!'!&$& "!**&"&&!

.32 %'!("!"*&"&&(%%'&"!!

&&255***''54

6&! 99..

'!9'&! 7 7: ;

7"')%! 7 <

&  1,

: 8&  = = ?

##44!!   = =

&#%%+   = -

: >#& . -1,

##4>#& . 1,

: 9&  1,

,'%@&A   = 

3&9& 9  = 

3&& 9 .3

3& IB = <B

9#4!!  < = --

9#>#& ) - = 

#%& DB = B

#%&1&&' EB = B

NOTE 1

123

  * ,1

PIC18F2221/2321/4221/4321 FAMILY

*+%!,-./.*+!

01'((),1

!"

  !"#$%&"' ()"&'"!&)&#*&&&#

 4!!*!"&#

- '!#&.0

1,2 1!'!&$& "!**&"&&!

.32 %'!("!"*&"&&(%%'&"!!

&&255***''54

6&! 99..

'!9'&! 7 7: ;

7"')%! 7 <

&  ?1,

: 8&  <  

&#%%    

,&&4!! - .3

: >#& . ?1,

.$!##>#& . -? - 

: 9&  ?1,

.$!##9&  -? - 

,&&>#& ) - - -

,&&9& 9   

,&&&.$!## C  = =

DEXPOSED D2

NOTE 1

TOP VIEW BOTTOM VIEW

PAD

  * ,1

PIC18F2221/2321/4221/4321 FAMILY

*+%!,-./.*+!

01'((),1

&&255***''54

PIC18F2221/2321/4221/4321 FAMILY

12#('#

!"

  !"#$%&"' ()"&'"!&)&#*&&&#

 '!!#.#&"#'#%!&"!!#%!&"!!!&$#''!#

- '!#&.0

1,2 1!'!&$& "!**&"&&!

.32 %'!("!"*&"&&(%%'&"!!

&&255***''54

6&! 99..

'!9'&! 7 7: ;

7"')%! 7 <

&  ?1,

: 8&  = = 

##44!!  ?  <

&#%%   = =

: >#& .  < <

##4>#& .  - ?

: 9&    

3&9& 9   

3&& 9 .3

9#4!!   = 

3& IB B <B

9#>#& )  = -<

NOTE 1

  * ,-1

PIC18F2221/2321/4221/4321 FAMILY

3.

!"

  !"#$%&"' ()"&'"!&)&#*&&&#

 +%&,&!&

 '!#&.0

1,2 1!'!&$& "!**&"&&!

&&255***''54

6&! 7,8.

'!9'&! 7 7: ;

7"')%! 7 

&  1,

&&  = = 

##44!!   = 

1!&&   = =

"#&"#>#& .  = ?

##4>#& . < = <

: 9&  < = 

&& 9  = 

9#4!!  < = 

69#>#& ) - = 

9*9#>#& )  = -

: *+ 1 = = 

NOTE 1

123

A1 b1

  * ,?1

PIC18F2221/2321/4221/4321 FAMILY

33*+%!,-/*+!

!"

  !"#$%&"' ()"&'"!&)&#*&&&#

 4!!*!"&#

- '!#&.0

1,2 1!'!&$& "!**&"&&!

.32 %'!("!"*&"&&(%%'&"!!

&&255***''54

6&! 99..

'!9'&! 7 7: ;

7"')%! 7 

&  ?1,

: 8&  <  

&#%%    

,&&4!! - .3

: >#& . <1,

.$!##>#& . ?- ? ?<

: 9&  <1,

.$!##9&  ?- ? ?<

,&&>#& )  - -<

,&&9& 9 -  

,&&&.$!## C  = =

DEXPOSED

PAD

NOTE 1

BOTTOM VIEW

TOP VIEW

A3 A1

  * ,-1

PIC18F2221/2321/4221/4321 FAMILY

33*+%!,-/*+!

&&255***''54

PIC18F2221/2321/4221/4321 FAMILY

3341*+546/6/6%'4*+

!"

  !"#$%&"' ()"&'"!&)&#*&&&#

 ,'%!&!&D!E' 

- '!!#.#&"#'#%!&"!!#%!&"!!!&$#''!#

 '!#&.0

1,2 1!'!&$& "!**&"&&!

.32 %'!("!"*&"&&(%%'&"!!

&&255***''54

6&! 99..

'!9'&! 7 7: ;

7"')%9#! 7 

9#&  <1,

: 8&  = = 

##44!!    

&#%%   = 

3&9& 9  ? 

3&& 9 .3

3& IB -B B

: >#& . 1,

: 9&  1,

##4>#& . 1,

##49&  1,

9#4!!   = 

9#>#& ) - - 

#%& DB B -B

#%&1&&' EB B -B

NOTE 1 NOTE 2

123

  * ,?1

PIC18F2221/2321/4221/4321 FAMILY

3341*+546/6/6%'4*+

&&255***''54

PIC18F2221/2321/4221/4321 FAMILY

APPENDIX A: REVISION HISTORY

Revision A (July 2005)

Original data sheet for PIC18F2221/2321/4221/4321

devices.

Revision B (August 2006)

Updated Section 26.0 “Electrical Characteristic”.

Revision C (October 2006)

This revision includes updates to the packaging

diagrams.

Revision D (January 2007)

This revision includes updates to the packaging

diagrams.

Revision E (February 2007)

This revision includes updates to the packaging

diagrams.

Revision F (September 2009)

This revision includes a new chapter, Section 2.0

“Guidelines for Getting Started with PIC18F

Microcontrollers”. There are also updates to

Section 27.0 “Electrical Characteristics”,

Section 28.0 “Packaging Information” and minor

text edits throughout document.

PIC18F2221/2321/4221/4321 FAMILY

APPENDIX B: DEVICE

DIFFERENCES

The differences between the devices listed in this data

sheet are shown in Table B-1.

TABLE B-1: DEVICE DIFFERENCES

Features PIC18F2221 PIC18F2321 PIC18F4221 PIC18F4321

Program Memory (Bytes) 4096 8192 4096 8192

Program Memory (Instructions) 2048 4096 2048 4096

Interrupt Sources 19 19 20 20

I/O Ports Ports A, B, C, (E) Ports A, B, C, (E) Ports A, B, C, D, E Ports A, B, C, D, E

Capture/Compare/PWM Modules 2 2 1 1

Enhanced Capture/Compare/

PWM Modules

0011

Parallel Communications (PSP) No No Yes Yes

10-Bit Analog-to-Digital Module 10 input channels 10 input channels 13 input channels 13 input channels

Packages 28-pin SPDIP

28-pin SOIC

28-pin SSOP

28-pin QFN

28-pin SPDIP

28-pin SOIC

28-pin SSOP

28-pin QFN

40-pin PDIP

44-pin TQFP

44-pin QFN

40-pin PDIP

44-pin TQFP

44-pin QFN

PIC18F2221/2321/4221/4321 FAMILY

APPENDIX C: CONVERSION

CONSIDERATIONS

This appendix discusses the considerations for

converting from previous versions of a device to the

ones listed in this data sheet. Typically, these changes

are due to the differences in the process technology

used. An example of this type of conversion is from a

PIC16C74A to a PIC16C74B.

The PIC18F2221/2321/4221/4321 family of devices is

functionally the same as the PIC18F4320 family. Code

written for a PIC18F4320 will generally work on a

PIC18F4321 with few or no changes.

The following is a list of changes the user should be

aware of when migrating an application from the

PIC18F4320 to the PIC18F4321. Code written for the

PIC18F4321 may not run as expected due to these

differences.

1. Entry to power-managed modes has changed.

Modifying the SCS1:SCS0 bits (OSCCON<1:0>)

immediately changes the current clock source. It

is not necessary to execute a SLEEP instruction

to change clock sources. Refer to Section 4.1.2

“Entering Power-Managed Modes” for details.

2. Exit from power-managed modes has changed.

A WDT wake or interrupt does not cause an

automatic return to PRI_RUN mode. The

controller will execute code while continuing to

use the current clock source. If the controller

was operating in RC_IDLE or RC_RUN mode,

an interrupt will cause entry to RC_RUN mode

until code selects another power-managed

mode. Refer to Section 4.4 “Idle Modes” for

details.

3. The extended instruction set can be con-

figured as enabled using the XINST bit

(CONFIG4L<6>). The access memory map is

also modified when the extended instruction set

is enabled. Refer to Section 6.5 “Data Memory

and the Extended Instruction Set” and

Section 24.2 “Extended Instruction Set” for

details.

4. There may also be changes to the electrical spec-

ifications. Refer to Section 27.0 “Electrical

Characteristics” for details.

APPENDIX D: MIGRATION FROM

BASELINE TO

ENHANCED DEVICES

This section discusses how to migrate from a Baseline

device (i.e., PIC16C5X) to an Enhanced MCU device

(i.e., PIC18FXXX).

The following are the list of modifications over the

PIC16C5X microcontroller family:

Not Currently Available

PIC18F2221/2321/4221/4321 FAMILY

APPENDIX E: MIGRATION FROM

MID-RANGE TO

ENHANCED DEVICES

A detailed discussion of the differences between the

mid-range MCU devices (i.e., PIC16CXXX) and the

Enhanced devices (i.e., PIC18FXXX) is provided in

AN716, “Migrating Designs from PIC16C74A/74B to

PIC18C442”. The changes discussed, while device

specific, are generally applicable to all mid-range to

Enhanced device migrations.

This Application Note is available as Literature Number

DS00716.

APPENDIX F: MIGRATION FROM

HIGH-END TO

ENHANCED DEVICES

A detailed discussion of the migration pathway and

differences between the high-end MCU devices (i.e.,

PIC17CXXX) and the Enhanced devices (i.e.,

PIC18FXXX) is provided in AN726, “PIC17CXXX to

PIC18CXXX Migration”.

This Application Note is available as Literature Number

DS00726.

PIC18F2221/2321/4221/4321 FAMILY

INDEX

A/D ................................................................................... 233

Acquisition Requirements ........................................ 238

ADCON0 Register .................................................... 233

ADCON1 Register .................................................... 233

ADCON2 Register .................................................... 233

ADRESH Register ............................................ 233, 236

ADRESL Register .................................................... 233

Analog Port Pins, Configuring .................................. 240

Associated Registers ............................................... 242

Configuring the Module ............................................ 237

Conversion Clock (TAD) ........................................... 239

Conversion Requirements ....................................... 371

Conversion Status (GO/DONE Bit) .......................... 236

Conversions ............................................................. 241

Converter Characteristics ........................................ 370

Converter Interrupt, Configuring .............................. 237

Discharge ................................................................. 241

Operation in Power-Managed Modes ...................... 240

Selecting and Configuring Acquisition Time ............ 239

Special Event Trigger (CCP) .................................... 242

Special Event Trigger (ECCP) ................................. 154

Use of the CCP2 Trigger .......................................... 242

Absolute Maximum Ratings ............................................. 333

AC (Timing) Characteristics ............................................. 352

Load Conditions for Device Timing

Specifications ................................................... 353

Parameter Symbology ............................................. 352

Temperature and Voltage Specifications ................. 353

Timing Conditions .................................................... 353

AC Characteristics

Internal RC Accuracy ............................................... 355

Access Bank

Mapping with Indexed Literal Offset

Addressing Mode ............................................... 77

ACKSTAT ........................................................................ 201

ACKSTAT Status Flag ..................................................... 201

ADCON0 Register ............................................................ 233

GO/DONE Bit ........................................................... 236

ADCON1 Register ............................................................ 233

ADCON2 Register ............................................................ 233

ADDFSR .......................................................................... 322

ADDLW ............................................................................ 285

ADDULNK ........................................................................ 322

ADDWF ............................................................................ 285

ADDWFC ......................................................................... 286

ADRESH Register ............................................................ 233

ADRESL Register .................................................... 233, 236

Analog-to-Digital Converter. See A/D.

ANDLW ............................................................................ 286

ANDWF ............................................................................ 287

Assembler

MPASM Assembler .................................................. 330

Auto-Wake-up on Sync Break Character ......................... 226

Bank Select Register (BSR) ............................................... 65

Baud Rate Generator ....................................................... 197

BC .................................................................................... 287

BCF .................................................................................. 288

BF .................................................................................... 201

BF Status Flag ................................................................. 201

Block Diagrams

A/D ........................................................................... 236

Analog Input Model .................................................. 237

Baud Rate Generator .............................................. 197

Capture Mode Operation ......................................... 147

Comparator Analog Input Model .............................. 247

Comparator I/O Operating Modes ........................... 244

Comparator Output .................................................. 246

Comparator Voltage Reference ............................... 250

Comparator Voltage Reference Output

Buffer Example ................................................ 251

Compare Mode Operation ....................................... 148

Device Clock .............................................................. 35

Enhanced PWM ....................................................... 155

EUSART Receive .................................................... 225

EUSART Transmit ................................................... 222

External Power-on Reset Circuit

(Slow VDD Power-up) ........................................ 49

Fail-Safe Clock Monitor ........................................... 272

Generic I/O Port ....................................................... 111

High/Low-Voltage Detect with External Input .......... 254

HSPLL ....................................................................... 31

Interrupt Logic ............................................................ 98

INTOSC and PLL ....................................................... 32

MSSP (I2C Master Mode) ........................................ 195

MSSP (I2C Mode) .................................................... 176

MSSP (SPI Mode) ................................................... 167

On-Chip Reset Circuit ................................................ 47

PIC18F2221/2321 ..................................................... 12

PIC18F4221/4321 ..................................................... 13

PORTD and PORTE (Parallel Slave Port) ............... 126

PWM Operation (Simplified) .................................... 150

Reads from Flash Program Memory ......................... 83

Single Comparator ................................................... 245

Table Read Operation ............................................... 79

Table Write Operation ............................................... 80

Table Writes to Flash Program Memory .................... 85

Timer0 in 16-Bit Mode ............................................. 130

Timer0 in 8-Bit Mode ............................................... 130

Timer1 ..................................................................... 134

Timer1 (16-Bit Read/Write Mode) ............................ 134

Timer2 ..................................................................... 140

Timer3 ..................................................................... 142

Timer3 (16-Bit Read/Write Mode) ............................ 142

Watchdog Timer ...................................................... 269

BN .................................................................................... 288

BNC ................................................................................. 289

BNN ................................................................................. 289

BNOV .............................................................................. 290

BNZ ................................................................................. 290

BOR. See Brown-out Reset.

BOV ................................................................................. 293

BRA ................................................................................. 291

Break Character (12-Bit) Transmit and Receive .............. 227

BRG. See Baud Rate Generator.

Brown-out Reset (BOR) ..................................................... 50

Detecting ................................................................... 50

Disabling in Sleep Mode ............................................ 50

Software Enabled ...................................................... 50

BSF .................................................................................. 291

BTFSC ............................................................................. 292

BTFSS ............................................................................. 292

BTG ................................................................................. 293

BZ .................................................................................... 294

PIC18F2221/2321/4221/4321 FAMILY

C Compilers

MPLAB C18 .............................................................330

MPLAB C30 .............................................................330

CALL ................................................................................ 294

CALLW .............................................................................323

Capture (CCP Module) ..................................................... 147

Associated Registers ............................................... 149

CCP Pin Configuration .............................................147

CCPRxH:CCPRxL Registers ................................... 147

Prescaler ..................................................................147

Software Interrupt .................................................... 147

Timer1/Timer3 Mode Selection ................................ 147

Capture (ECCP Module) .................................................. 154

Capture/Compare/PWM (CCP) ........................................145

Capture Mode. See Capture.

CCPRxH Register .................................................... 146

CCPRxL Register ..................................................... 146

Compare Mode. See Compare.

Interaction of Two CCP Modules ............................. 146

Module Configuration ............................................... 146

Pin Assignment ........................................................ 146

Timer Resources ...................................................... 146

Clock Sources .................................................................... 35

Selecting the 31 kHz Source ......................................36

Selection Using OSCCON Register ...........................36

CLRF ................................................................................295

CLRWDT ..........................................................................295

Code Examples

16 x 16 Signed Multiply Routine ................................ 96

16 x 16 Unsigned Multiply Routine ............................ 96

8 x 8 Signed Multiply Routine .................................... 95

8 x 8 Unsigned Multiply Routine ................................ 95

Address Masking ..................................................... 182

Changing Between Capture Prescalers ................... 147

Computed GOTO Using an Offset Value ................... 62

Data EEPROM Read .................................................91

Data EEPROM Refresh Routine ................................ 92

Data EEPROM Write .................................................91

Erasing a Flash Program Memory Row .....................84

Fast Register Stack .................................................... 62

How to Clear RAM (Bank 1) Using Indirect

Addressing ......................................................... 73

Implementing a Real-Time Clock Using a

Timer1 Interrupt Service .................................. 137

Initializing PORTA .................................................... 111

Initializing PORTB .................................................... 114

Initializing PORTC .................................................... 117

Initializing PORTD .................................................... 120

Initializing PORTE .................................................... 123

Loading the SSPBUF (SSPSR) Register ................. 170

Reading a Flash Program Memory Word .................. 83

Saving STATUS, WREG and BSR

Registers in RAM ............................................. 109

Writing to Flash Program Memory ....................... 86–87

Code Protection ....................................................... 259, 274

Associated Registers ............................................... 275

Configuration Register Protection ............................277

Data EEPROM ......................................................... 277

Program Memory ..................................................... 275

COMF ............................................................................... 296

Comparator ...................................................................... 243

Analog Input Connection Considerations ................. 247

Associated Registers ............................................... 247

Configuration ............................................................ 244

Effects of a Reset .................................................... 246

Interrupts ................................................................. 246

Operation ................................................................. 245

Operation During Sleep ........................................... 246

Outputs .................................................................... 245

Reference ................................................................ 245

External Signal ................................................ 245

Internal Signal .................................................. 245

Response Time ........................................................ 245

Comparator Specifications ............................................... 350

Comparator Voltage Reference ....................................... 249

Accuracy and Error .................................................. 250

Associated Registers ............................................... 251

Configuring .............................................................. 249

Connection Considerations ...................................... 250

Effects of a Reset .................................................... 250

Operation During Sleep ........................................... 250

Compare (CCP Module) .................................................. 148

CCPRx Register ...................................................... 148

Pin Configuration ..................................................... 148

Software Interrupt .................................................... 148

Special Event Trigger .............................. 143, 148, 242

Timer1/Timer3 Mode Selection ................................ 148

Compare (ECCP Module) ................................................ 154

Special Event Trigger .............................................. 154

Computed GOTO ............................................................... 62

Configuration Bits ............................................................ 259

Context Saving During Interrupts ..................................... 109

Conversion Considerations .............................................. 387

CPFSEQ .......................................................................... 296

CPFSGT .......................................................................... 297

CPFSLT ........................................................................... 297

Crystal Oscillator/Ceramic Resonator ................................ 29

Customer Change Notification Service ............................ 399

Customer Notification Service ......................................... 399

Customer Support ............................................................ 399

Data Addressing Modes .................................................... 73

Comparing Options with the Extended

Instruction Set Enabled ..................................... 76

Direct ......................................................................... 73

Indexed Literal Offset ................................................ 75

Instructions Affected .......................................... 75

Indirect ....................................................................... 73

Inherent and Literal .................................................... 73

Data EEPROM Memory ..................................................... 89

Associated Registers ................................................. 93

EEADR Register ........................................................ 89

EECON1 Register ...................................................... 89

EECON2 Register ...................................................... 89

EEDATA Register ...................................................... 89

Operation During Code-Protect ................................. 92

Protection Against Spurious Write ............................. 92

Reading ..................................................................... 91

Using ......................................................................... 92

Write Verify ................................................................ 91

Writing ....................................................................... 91

Data Memory ..................................................................... 65

Access Bank .............................................................. 67

and the Extended Instruction Set .............................. 75

Bank Select Register (BSR) ...................................... 65

General Purpose Registers ....................................... 67

Map for PIC18F2221/2321/4221/4321 Family ........... 66

Special Function Registers ........................................ 68

PIC18F2221/2321/4221/4321 FAMILY

DAW ................................................................................. 298

DC Characteristics ........................................................... 347

Power-Down and Supply Current ............................ 337

Supply Voltage ......................................................... 336

DCFSNZ .......................................................................... 299

DECF ............................................................................... 298

DECFSZ ........................................................................... 299

Development Support ...................................................... 329

Device Differences ........................................................... 386

Device Overview .................................................................. 9

Details on Individual Family Members ....................... 10

Features (table) .......................................................... 11

New Core Features ...................................................... 9

Other Special Features .............................................. 10

Device Reset Timers .......................................................... 51

Oscillator Start-up Timer (OST) ................................. 51

PLL Lock Time-out ..................................................... 51

Power-up Timer (PWRT) ........................................... 51

Time-out Sequence .................................................... 51

Direct Addressing ............................................................... 74

Effect on Standard PIC MCU Instructions ........................ 326

Effects of Power-Managed Modes on Various

Clock Sources ............................................................ 38

Electrical Characteristics .................................................. 333

Enhanced Capture/Compare/PWM (ECCP) .................... 153

Associated Registers ............................................... 166

Capture and Compare Modes .................................. 154

Capture Mode. See Capture (ECCP Module).

Outputs and Configuration ....................................... 154

Pin Configurations for ECCP1 ................................. 154

PWM Mode. See PWM (ECCP Module).

Standard PWM Mode ............................................... 154

Timer Resources ...................................................... 154

Enhanced PWM Mode. See PWM (ECCP Module). ........ 155

Enhanced Universal Synchronous Asynchronous Receiver

Transmitter (EUSART). See EUSART.

Equations

A/D Acquisition Time ................................................ 238

A/D Minimum Charging Time ................................... 238

Calculating the Minimum Required

Acquisition Time .............................................. 238

Errata ................................................................................... 8

EUSART

Asynchronous Mode ................................................ 221

12-Bit Break Transmit and Receive ................. 227

Associated Registers, Receive ........................ 225

Associated Registers, Transmit ....................... 223

Auto-Wake-up on Sync Break ......................... 226

Receiver ........................................................... 224

Setting up 9-Bit Mode with Address Detect ..... 224

Transmitter ....................................................... 221

Baud Rate Generator

Operation in Power-Managed Mode ................ 215

Baud Rate Generator (BRG) .................................... 215

Associated Registers ....................................... 216

Auto-Baud Rate Detect .................................... 219

Baud Rate Error, Calculating ........................... 216

Baud Rates, Asynchronous Modes ................. 217

High Baud Rate Select (BRGH Bit) ................. 215

Sampling .......................................................... 215

Synchronous Master Mode ...................................... 228

Associated Registers, Receive ........................ 230

Associated Registers, Transmit ....................... 229

Reception ........................................................ 230

Transmission ................................................... 228

Synchronous Slave Mode ........................................ 231

Associated Registers, Receive ........................ 232

Associated Registers, Transmit ....................... 231

Reception ........................................................ 232

Transmission ................................................... 231

Extended Instruction Set

ADDFSR .................................................................. 322

ADDULNK ............................................................... 322

and Using MPLAB Tools ......................................... 328

CALLW .................................................................... 323

Considerations for Use ............................................ 326

MOVSF .................................................................... 323

MOVSS .................................................................... 324

PUSHL ..................................................................... 324

SUBFSR .................................................................. 325

SUBULNK ................................................................ 325

Syntax ...................................................................... 321

External Clock Input ........................................................... 30

Fail-Safe Clock Monitor ........................................... 259, 272

Exiting Operation ..................................................... 272

Interrupts in Power-Managed Modes ...................... 273

POR or Wake From Sleep ....................................... 273

WDT During Oscillator Failure ................................. 272

Fast Register Stack ........................................................... 62

Firmware Instructions ...................................................... 279

Flash Program Memory ..................................................... 79

Associated Registers ................................................. 87

Control Registers ....................................................... 80

EECON1 and EECON2 ..................................... 80

TABLAT (Table Latch) Register ........................ 82

TBLPTR (Table Pointer) Register ...................... 82

Erase Sequence ........................................................ 84

Erasing ...................................................................... 84

Operation During Code-Protect ................................. 87

Reading ..................................................................... 83

Table Pointer

Boundaries ........................................................ 82

Boundaries Based on Operation ....................... 82

Operations with TBLRD and TBLWT (table) ..... 82

Table Reads and Table Writes .................................. 79

Write Sequence ......................................................... 85

Writing ....................................................................... 85

Protection Against Spurious Writes ................... 87

Unexpected Termination ................................... 87

Write Verify ........................................................ 87

FSCM. See Fail-Safe Clock Monitor.

GOTO .............................................................................. 300

Hardware Multiplier ............................................................ 95

Introduction ................................................................ 95

Operation ................................................................... 95

Performance Comparison .......................................... 95

PIC18F2221/2321/4221/4321 FAMILY

High/Low-Voltage Detect ................................................. 253

Applications .............................................................. 256

Associated Registers ............................................... 257

Characteristics ......................................................... 351

Current Consumption ...............................................255

Effects of a Reset ..................................................... 257

Operation .................................................................254

During Sleep .................................................... 257

Setup ........................................................................ 255

Start-up Time ........................................................... 255

Typical Application ................................................... 256

HLVD. See High/Low-Voltage Detect. ............................. 253

I/O Ports ........................................................................... 111

I2C Mode (MSSP)

Acknowledge Sequence Timing ............................... 204

Associated Registers ............................................... 210

Baud Rate Generator ...............................................197

Bus Collision

During a Repeated Start Condition .................. 208

During a Start Condition ................................... 206

During a Stop Condition ................................... 209

Clock Arbitration .......................................................198

Clock Stretching .......................................................190

10-Bit Slave Receive Mode (SEN = 1) ............. 190

10-Bit Slave Transmit Mode ............................. 190

7-Bit Slave Receive Mode (SEN = 1) ............... 190

7-Bit Slave Transmit Mode ............................... 190

Clock Synchronization and the CKP Bit ................... 191

Effects of a Reset ..................................................... 205

General Call Address Support ................................. 194

I2C Clock Rate w/BRG ............................................. 197

Master Mode ............................................................ 195

Operation ......................................................... 196

Reception ......................................................... 201

Repeated Start Condition Timing ..................... 200

Start Condition Timing ..................................... 199

Transmission .................................................... 201

Multi-Master Communication, Bus Collision

and Arbitration .................................................. 205

Multi-Master Mode ...................................................205

Operation .................................................................181

Read/Write Bit Information (R/W Bit) ....................... 181

Read/Write Bit Information (R/W Bit) ....................... 183

Registers .................................................................. 176

Serial Clock (RC3/SCK/SCL) ................................... 183

Slave Mode ..............................................................181

Address Masking ............................................. 182

Addressing ....................................................... 181

Reception ......................................................... 183

Transmission .................................................... 183

Sleep Operation ....................................................... 205

Stop Condition Timing ..............................................204

ID Locations ............................................................. 259, 277

INCF .................................................................................300

INCFSZ ............................................................................ 301

In-Circuit Debugger .......................................................... 277

In-Circuit Serial Programming (ICSP) ...................... 259, 277

Single-Supply ........................................................... 277

Indexed Literal Offset Addressing

and Standard PIC18 Instructions ............................. 326

Indexed Literal Offset Mode ............................................. 326

Indirect Addressing ............................................................ 74

INFSNZ ............................................................................301

Initialization Conditions for all Registers ...................... 55–58

Instruction Cycle ................................................................ 63

Clocking Scheme ....................................................... 63

Instruction Flow/Pipelining ................................................. 63

Instruction Set .................................................................. 279

ADDLW .................................................................... 285

ADDWF .................................................................... 285

ADDWF (Indexed Literal Offset Mode) .................... 327

ADDWFC ................................................................. 286

ANDLW .................................................................... 286

ANDWF .................................................................... 287

BC ............................................................................ 287

BCF ......................................................................... 288

BN ............................................................................ 288

BNC ......................................................................... 289

BNN ......................................................................... 289

BNOV ...................................................................... 290

BNZ ......................................................................... 290

BOV ......................................................................... 293

BRA ......................................................................... 291

BSF .......................................................................... 291

BSF (Indexed Literal Offset Mode) .......................... 327

BTFSC ..................................................................... 292

BTFSS ..................................................................... 292

BTG ......................................................................... 293

BZ ............................................................................ 294

CALL ........................................................................ 294

CLRF ....................................................................... 295

CLRWDT ................................................................. 295

COMF ...................................................................... 296

CPFSEQ .................................................................. 296

CPFSGT .................................................................. 297

CPFSLT ................................................................... 297

DAW ........................................................................ 298

DCFSNZ .................................................................. 299

DECF ....................................................................... 298

DECFSZ .................................................................. 299

Extended Instruction Set ......................................... 321

General Format ........................................................ 281

GOTO ...................................................................... 300

INCF ........................................................................ 300

INCFSZ .................................................................... 301

INFSNZ .................................................................... 301

IORLW ..................................................................... 302

IORWF ..................................................................... 302

LFSR ....................................................................... 303

MOVF ...................................................................... 303

MOVFF .................................................................... 304

MOVLB .................................................................... 304

MOVLW ................................................................... 305

MOVWF ................................................................... 305

MULLW .................................................................... 306

MULWF .................................................................... 306

NEGF ....................................................................... 307

NOP ......................................................................... 307

Opcode Field Descriptions ....................................... 280

POP ......................................................................... 308

PUSH ....................................................................... 308

RCALL ..................................................................... 309

RESET ..................................................................... 309

RETFIE .................................................................... 310

RETLW .................................................................... 310

RETURN .................................................................. 311

RLCF ....................................................................... 311

RLNCF ..................................................................... 312

RRCF ....................................................................... 312

PIC18F2221/2321/4221/4321 FAMILY

RRNCF .................................................................... 313

SETF ........................................................................ 313

SETF (Indexed Literal Offset Mode) ........................ 327

SLEEP ..................................................................... 314

Standard Instructions ............................................... 279

SUBFWB .................................................................. 314

SUBLW .................................................................... 315

SUBWF .................................................................... 315

SUBWFB .................................................................. 316

SWAPF .................................................................... 316

TBLRD ..................................................................... 317

TBLWT ..................................................................... 318

TSTFSZ ................................................................... 319

XORLW .................................................................... 319

XORWF .................................................................... 320

INTCON Registers ..................................................... 99–101

Inter-Integrated Circuit. See I2C.

Internal Oscillator Block ..................................................... 32

Adjustment ................................................................. 32

INTIO Modes .............................................................. 32

INTOSC Frequency Drift ............................................ 33

INTOSC Output Frequency ........................................ 32

OSCTUNE Register ................................................... 32

PLL in INTOSC Modes .............................................. 33

Internal RC Oscillator

Use with WDT .......................................................... 269

Internet Address ............................................................... 399

Interrupt Sources ............................................................. 259

A/D Conversion Complete ....................................... 237

Capture Complete (CCP) ......................................... 147

Compare Complete (CCP) ....................................... 148

Interrupt-on-Change (RB7:RB4) .............................. 114

INTx Pin ................................................................... 109

PORTB, Interrupt-on-Change .................................. 109

TMR0 ....................................................................... 109

TMR0 Overflow ........................................................ 131

TMR1 Overflow ........................................................ 133

TMR2 to PR2 Match (PWM) ............................ 150, 155

TMR3 Overflow ................................................ 141, 143

Interrupts ............................................................................ 97

INTOSC, INTRC. See Internal Oscillator Block.

IORLW ............................................................................. 302

IORWF ............................................................................. 302

IPR Registers ................................................................... 106

LFSR ................................................................................ 303

Low-Voltage ICSP Programming. See Single-Supply ICSP

Programming

Master Clear (MCLR) ......................................................... 49

Master Synchronous Serial Port (MSSP). See MSSP.

Memory Organization ......................................................... 59

Data Memory ............................................................. 65

Program Memory ....................................................... 59

Memory Programming Requirements .............................. 349

Microchip Internet Web Site ............................................. 399

Migration from Baseline to Enhanced Devices ................ 387

Migration from High-End to Enhanced Devices ............... 388

Migration from Mid-Range to Enhanced Devices ............ 388

MOVF ............................................................................... 303

MOVFF ............................................................................ 304

MOVLB ............................................................................ 304

MOVLW ........................................................................... 305

MOVSF ............................................................................ 323

MOVSS ............................................................................ 324

MOVWF ........................................................................... 305

MPLAB ASM30 Assembler, Linker, Librarian .................. 330

MPLAB ICD 2 In-Circuit Debugger .................................. 331

MPLAB ICE 2000 High-Performance Universal

In-Circuit Emulator ................................................... 331

MPLAB Integrated Development Environment

Software .................................................................. 329

MPLAB PM3 Device Programmer ................................... 331

MPLAB REAL ICE In-Circuit Emulator System ............... 331

MPLINK Object Linker/MPLIB Object Librarian ............... 330

MSSP

ACK Pulse ....................................................... 181, 183

Control Registers (general) ..................................... 167

I2C Mode. See I2C Mode.

Module Overview ..................................................... 167

SPI Master/Slave Connection .................................. 171

SPI Mode. See SPI Mode.

SSPBUF Register .................................................... 172

SSPSR Register ...................................................... 172

MULLW ............................................................................ 306

MULWF ............................................................................ 306

NEGF ............................................................................... 307

NOP ................................................................................. 307

Oscillator Configuration ..................................................... 29

EC .............................................................................. 29

ECIO .......................................................................... 29

HS .............................................................................. 29

HSPLL ....................................................................... 29

Internal Oscillator Block ............................................. 32

INTIO1 ....................................................................... 29

INTIO2 ....................................................................... 29

LP .............................................................................. 29

RC ............................................................................. 29

RCIO .......................................................................... 29

XT .............................................................................. 29

Oscillator Selection .......................................................... 259

Oscillator Start-up Timer (OST) ................................... 38, 51

Oscillator Switching ........................................................... 35

Oscillator Transitions ......................................................... 36

Oscillator, Timer1 ..................................................... 133, 143

Oscillator, Timer3 ............................................................. 141

Packaging Information ..................................................... 373

Marking .................................................................... 373

Parallel Slave Port (PSP) ......................................... 120, 126

Associated Registers ............................................... 127

CS (Chip Select) ...................................................... 126

PORTD .................................................................... 126

RD (Read Input) ...................................................... 126

Select (PSPMODE Bit) .................................... 120, 126

WR (Write Input) ...................................................... 126

PICSTART Plus Development Programmer .................... 332

PIE Registers ................................................................... 104

Pin Functions

MCLR/VPP/RE3 ................................................... 14, 18

OSC1/CLKI/RA7 .................................................. 14, 18

OSC2/CLKO/RA6 ................................................ 14, 18

RA0/AN0 .............................................................. 15, 19

RA1/AN1 .............................................................. 15, 19

PIC18F2221/2321/4221/4321 FAMILY

RA2/AN2/VREF-/CVREF ........................................ 15, 19

RA3/AN3/VREF+ ................................................... 15, 19

RA4/T0CKI/C1OUT .............................................. 15, 19

RA5/AN4/SS/HLVDIN/C2OUT ............................. 15, 19

RB0/INT0/FLT0/AN12 .......................................... 16, 20

RB1/INT1/AN10 ................................................... 16, 20

RB2/INT2/AN8 ..................................................... 16, 20

RB3/AN9/CCP2 ................................................... 16, 20

RB4/KBI0/AN11 ................................................... 16, 20

RB5/KBI1/PGM .................................................... 16, 20

RB6/KBI2/PGC .................................................... 16, 20

RB7/KBI3/PGD .................................................... 16, 20

RC0/T1OSO/T13CKI ...........................................17, 21

RC1/T1OSI/CCP2 ................................................ 17, 21

RC2/CCP1 .................................................................17

RC2/CCP1/P1A ......................................................... 21

RC3/SCK/SCL ..................................................... 17, 21

RC4/SDI/SDA ...................................................... 17, 21

RC5/SDO ............................................................. 17, 21

RC6/TX/CK .......................................................... 17, 21

RC7/RX/DT .......................................................... 17, 21

RD0/PSP0 .................................................................. 22

RD1/PSP1 .................................................................. 22

RD2/PSP2 .................................................................. 22

RD3/PSP3 .................................................................. 22

RD4/PSP4 .................................................................. 22

RD5/PSP5/P1B ..........................................................22

RD6/PSP6/P1C .......................................................... 22

RD7/PSP7/P1D .......................................................... 22

RE0/RD/AN5 .............................................................. 23

RE1/WR/AN6 ............................................................. 23

RE2/CS/AN7 .............................................................. 23

VDD ....................................................................... 17, 23

VSS ....................................................................... 17, 23

Pinout I/O Descriptions

PIC18F2221/2321 ...................................................... 14

PIC18F4221/4321 ...................................................... 18

PIR Registers ................................................................... 102

PLL Frequency Multiplier ...................................................31

HSPLL Oscillator Mode .............................................. 31

Use with INTOSC ....................................................... 31

POP .................................................................................. 308

POR. See Power-on Reset.

PORTA

Associated Registers ............................................... 113

LATA Register .......................................................... 111

PORTA Register ...................................................... 111

TRISA Register ........................................................ 111

PORTB

Associated Registers ............................................... 116

LATB Register .......................................................... 114

PORTB Register ...................................................... 114

TRISB Register ........................................................ 114

PORTC

Associated Registers ............................................... 119

LATC Register ......................................................... 117

PORTC Register ...................................................... 117

RC3/SCK/SCL Pin ...................................................183

TRISC Register ........................................................117

PORTD

Associated Registers ............................................... 122

LATD Register ......................................................... 120

Parallel Slave Port (PSP) Function .......................... 120

PORTD Register ...................................................... 120

TRISD Register ........................................................120

PORTE

Associated Registers ............................................... 125

LATE Register ......................................................... 123

PORTE Register ...................................................... 123

PSP Mode Select (PSPMODE Bit) .......................... 120

TRISE Register ........................................................ 123

Power-Managed Modes ..................................................... 39

and A/D Operation ................................................... 240

and EUSART Operation .......................................... 215

and PWM Operation ................................................ 165

and SPI Operation ................................................... 175

Clock Sources ............................................................ 39

Clock Transitions and Status Indicators .................... 40

Effects on Clock Sources ........................................... 38

Entering ..................................................................... 39

Exiting Idle and Sleep Modes .................................... 45

By Interrupt ........................................................ 45

By Reset ............................................................ 45

By WDT Time-out .............................................. 45

Without an Oscillator Start-up Delay ................. 46

Idle Modes ................................................................. 43

PRI_IDLE ........................................................... 44

RC_IDLE ........................................................... 45

SEC_IDLE ......................................................... 44

Multiple Sleep Commands ......................................... 40

Run Modes ................................................................ 40

PRI_RUN ........................................................... 40

RC_RUN ............................................................ 41

SEC_RUN ......................................................... 40

Sleep Mode ............................................................... 43

Summary (table) ........................................................ 39

Power-on Reset (POR) ...................................................... 49

Power-up Timer (PWRT) ........................................... 51

Time-out Sequence ................................................... 51

Power-up Delays ............................................................... 38

Power-up Timer (PWRT) ................................................... 38

Prescaler

Timer2 ..................................................................... 156

Prescaler, Timer0 ............................................................ 131

Prescaler, Timer2 ............................................................ 151

PRI_IDLE Mode ................................................................. 44

PRI_RUN Mode ................................................................. 40

Program Counter ............................................................... 60

PCL, PCH and PCU Registers .................................. 60

PCLATH and PCLATU Registers .............................. 60

Program Memory

and Extended Instruction Set .................................... 77

Instructions ................................................................ 64

Two-Word .......................................................... 64

Interrupt Vector .......................................................... 59

Look-up Tables .......................................................... 62

Map and Stack (diagram) .......................................... 59

Reset Vector .............................................................. 59

Program Verification ........................................................ 274

Programming, Device Instructions ................................... 279

PSP. See Parallel Slave Port.

Pulse-Width Modulation. See PWM (CCP Module) and

PWM (ECCP Module).

PUSH ............................................................................... 308

PUSH and POP Instructions .............................................. 61

PUSHL ............................................................................. 324

PWM (CCP Module)

Associated Registers ............................................... 152

Auto-Shutdown (CCP1 Only) ................................... 151

Duty Cycle ............................................................... 150

PIC18F2221/2321/4221/4321 FAMILY

Example Frequencies/Resolutions .......................... 151

Operation Setup ....................................................... 151

Period ....................................................................... 150

TMR2 to PR2 Match ........................................ 150, 155

PWM (ECCP Module) ...................................................... 155

CCPR1H:CCPR1L Registers ................................... 155

Duty Cycle ................................................................ 156

Effects of a Reset ..................................................... 165

Enhanced PWM Auto-Shutdown ............................. 162

Example Frequencies/Resolutions .......................... 156

Full-Bridge Application Example .............................. 160

Full-Bridge Mode ...................................................... 159

Direction Change ............................................. 160

Half-Bridge Mode ..................................................... 158

Half-Bridge Output Mode Applications

Example ........................................................... 158

Operation in Power-Managed Modes ...................... 165

Operation with Fail-Safe Clock Monitor ................... 165

Output Configurations .............................................. 156

Output Relationships (Active-High) .......................... 157

Output Relationships (Active-Low) ........................... 157

Period ....................................................................... 155

Programmable Dead-Band Delay ............................ 162

Setup for PWM Operation ........................................ 165

Start-up Considerations ........................................... 164

Q Clock .................................................................... 151, 156

RAM. See Data Memory.

RC Oscillator

RCIO Oscillator Mode ................................................ 31

RC_IDLE Mode .................................................................. 45

RC_RUN Mode .................................................................. 41

RCALL ............................................................................. 309

RCON Register

Bit Status During Initialization .................................... 54

Reader Response ............................................................ 400

Registers

ADCON0 (A/D Control 0) ......................................... 233

ADCON1 (A/D Control 1) ......................................... 234

ADCON2 (A/D Control 2) ......................................... 235

BAUDCON (Baud Rate Control) .............................. 214

CCP1CON (Enhanced Capture/Compare/PWM

Control 1) ......................................................... 153

CCPxCON (CCPx Control) ...................................... 145

CMCON (Comparator Control) ................................ 243

CONFIG1H (Configuration 1 High) .......................... 260

CONFIG2H (Configuration 2 High) .......................... 262

CONFIG2L (Configuration 2 Low) ............................ 261

CONFIG3H (Configuration 3 High) .......................... 263

CONFIG4L (Configuration 4 Low) ............................ 264

CONFIG5H (Configuration 5 High) .......................... 265

CONFIG5L (Configuration 5 Low) ............................ 265

CONFIG6H (Configuration 6 High) .......................... 266

CONFIG6L (Configuration 6 Low) ............................ 266

CONFIG7H (Configuration 7 High) .......................... 267

CONFIG7L (Configuration 7 Low) ............................ 267

CVRCON (Comparator Voltage

Reference Control) .......................................... 249

DEVID1 (Device ID 1) .............................................. 268

DEVID2 (Device ID 2) .............................................. 268

ECCP1AS (ECCP Auto-Shutdown Control) ............. 163

ECCP1DEL (PWM Dead-Band Delay) .................... 162

EECON1 (Data EEPROM Control 1) ................... 81, 90

HLVDCON (High/Low-Voltage Detect Control) ....... 253

INTCON (Interrupt Control) ....................................... 99

INTCON2 (Interrupt Control 2) ................................ 100

INTCON3 (Interrupt Control 3) ................................ 101

IPR1 (Peripheral Interrupt Priority 1) ....................... 106

IPR2 (Peripheral Interrupt Priority 2) ....................... 107

OSCCON (Oscillator Control) .................................... 37

OSCTUNE (Oscillator Tuning) ................................... 33

PIE1 (Peripheral Interrupt Enable 1) ....................... 104

PIE2 (Peripheral Interrupt Enable 2) ....................... 105

PIR1 (Peripheral Interrupt Request (Flag) 1) ........... 102

PIR2 (Peripheral Interrupt Request (Flag) 2) ........... 103

RCON (Reset Control) ....................................... 48, 108

RCSTA (Receive Status and Control) ..................... 213

SSPADD(MSSP Address) ....................................... 180

SSPCON1 (MSSP Control 1, I2C Mode) ................. 178

SSPCON1 (MSSP Control 1, SPI Mode) ................ 169

SSPCON2 (MSSP Control 2, I2C Mode) ................. 179

SSPSTAT (MSSP Status, I2C Mode) ...................... 177

SSPSTAT (MSSP Status, SPI Mode) ...................... 168

STATUS .................................................................... 72

STKPTR (Stack Pointer) ............................................ 61

T0CON (Timer0 Control) ......................................... 129

T1CON (Timer1 Control) ......................................... 133

T2CON (Timer2 Control) ......................................... 139

T3CON (Timer3 Control) ......................................... 141

TRISE (PORTE/PSP Control) ................................. 124

TXSTA (Transmit Status and Control) ..................... 212

WDTCON (Watchdog Timer Control) ...................... 270

RESET ............................................................................. 309

Reset State of Registers .................................................... 54

Resets ....................................................................... 47, 259

Brown-out Reset (BOR) ........................................... 259

Oscillator Start-up Timer (OST) ............................... 259

Power-on Reset (POR) ............................................ 259

Power-up Timer (PWRT) ......................................... 259

RETFIE ............................................................................ 310

RETLW ............................................................................ 310

RETURN .......................................................................... 311

Return Address Stack ........................................................ 60

Associated Registers ................................................. 60

Return Stack Pointer (STKPTR) ........................................ 61

Revision History ............................................................... 385

RLCF ............................................................................... 311

RLNCF ............................................................................. 312

RRCF ............................................................................... 312

RRNCF ............................................................................ 313

SCK ................................................................................. 167

SDI ................................................................................... 167

SDO ................................................................................. 167

SEC_IDLE Mode ............................................................... 44

SEC_RUN Mode ................................................................ 40

Serial Clock, SCK ............................................................ 167

Serial Data In (SDI) .......................................................... 167

Serial Data Out (SDO) ..................................................... 167

Serial Peripheral Interface. See SPI Mode.

SETF ............................................................................... 313

Single-Supply ICSP Programming.

Slave Select (SS) ............................................................. 167

SLEEP ............................................................................. 314

Sleep

OSC1 and OSC2 Pin States ...................................... 38

PIC18F2221/2321/4221/4321 FAMILY

Software Simulator (MPLAB SIM) .................................... 330

Special Event Trigger. See Compare (CCP Mode).

Special Event Trigger. See Compare (ECCP Module).

Special Features of the CPU ............................................ 259

Special Function Registers ................................................ 68

Map ............................................................................68

SPI Mode (MSSP)

Associated Registers ............................................... 175

Bus Mode Compatibility ........................................... 175

Effects of a Reset ..................................................... 175

Enabling SPI I/O ...................................................... 171

Master Mode ............................................................ 172

Master/Slave Connection ......................................... 171

Operation .................................................................170

Operation in Power-Managed Modes ...................... 175

Serial Clock .............................................................. 167

Serial Data In ........................................................... 167

Serial Data Out ........................................................ 167

Slave Mode ..............................................................173

Slave Select .............................................................167

Slave Select Synchronization .................................. 173

SPI Clock ................................................................. 172

Typical Connection .................................................. 171

SS .................................................................................... 167

SSPOV ............................................................................. 201

SSPOV Status Flag .......................................................... 201

SSPSTAT Register

R/W Bit ............................................................. 181, 183

Stack Full/Underflow Resets .............................................. 62

SUBFSR ........................................................................... 325

SUBFWB ..........................................................................314

SUBLW ............................................................................315

SUBULNK ........................................................................325

SUBWF ............................................................................ 315

SUBWFB .......................................................................... 316

SWAPF ............................................................................316

Table Reads/Table Writes .................................................. 62

TBLRD .............................................................................317

TBLWT .............................................................................318

Time-out in Various Situations (table) ................................51

Timer0 .............................................................................. 129

Associated Registers ............................................... 131

Operation .................................................................130

Overflow Interrupt .................................................... 131

Prescaler ..................................................................131

Prescaler Assignment (PSA Bit) ..............................131

Prescaler Select (T0PS2:T0PS0 Bits) ..................... 131

Prescaler. See Prescaler, Timer0.

Reads and Writes in 16-Bit Mode ............................ 130

Source Edge Select (T0SE Bit) ................................ 130

Source Select (T0CS Bit) ......................................... 130

Switching Prescaler Assignment .............................. 131

Timer1 .............................................................................. 133

16-Bit Read/Write Mode ........................................... 135

Associated Registers ............................................... 137

Interrupt .................................................................... 136

Operation .................................................................134

Oscillator .......................................................... 133, 135

Layout Considerations ..................................... 136

Low-Power Option ........................................... 135

Overflow Interrupt .................................................... 133

Resetting, Using the CCP Special Event Trigger ..... 136

Special Event Trigger (ECCP) ................................. 154

TMR1H Register ...................................................... 133

TMR1L Register ....................................................... 133

Use as a Real-Time Clock ....................................... 136

Timer2 .............................................................................. 139

Associated Registers ............................................... 140

Interrupt ................................................................... 140

Operation ................................................................. 139

Output ...................................................................... 140

PR2 Register ................................................... 150, 155

TMR2 to PR2 Match Interrupt .................................. 155

TMR2-to-PR2 Match Interrupt ................................. 150

Timer3 .............................................................................. 141

16-Bit Read/Write Mode .......................................... 143

Associated Registers ............................................... 143

Operation ................................................................. 142

Oscillator .......................................................... 141, 143

Overflow Interrupt ............................................ 141, 143

Special Event Trigger (CCP) ................................... 143

TMR3H Register ...................................................... 141

TMR3L Register ....................................................... 141

Timing Diagrams

A/D Conversion ........................................................ 371

Acknowledge Sequence .......................................... 204

Asynchronous Reception ......................................... 225

Asynchronous Transmission .................................... 222

Asynchronous Transmission (Back to Back) ........... 222

Automatic Baud Rate Calculation ............................ 220

Auto-Wake-up Bit (WUE) During

Normal Operation ............................................ 226

Auto-Wake-up Bit (WUE) During Sleep ................... 226

Baud Rate Generator with Clock Arbitration ............ 198

BRG Overflow Sequence ......................................... 220

BRG Reset Due to SDA Arbitration During

Start Condition ................................................. 207

Brown-out Reset (BOR) ........................................... 357

Bus Collision During a Repeated Start

Condition (Case 1) ........................................... 208

Bus Collision During a Repeated Start

Condition (Case 2) ........................................... 208

Bus Collision During a Start Condition

(SCL = 0) ......................................................... 207

Bus Collision During a Stop Condition (Case 1) ...... 209

Bus Collision During a Stop Condition (Case 2) ...... 209

Bus Collision During Start Condition

(SDA Only) ...................................................... 206

Bus Collision for Transmit and Acknowledge .......... 205

Capture/Compare/PWM (All CCP Modules) ............ 359

CLKO and I/O .......................................................... 356

Clock Synchronization ............................................. 191

Clock/Instruction Cycle .............................................. 63

EUSART Synchronous Receive (Master/Slave) ...... 369

EUSART Synchronous Transmission

(Master/Slave) ................................................. 369

Example SPI Master Mode (CKE = 0) ..................... 361

Example SPI Master Mode (CKE = 1) ..................... 362

Example SPI Slave Mode (CKE = 0) ....................... 363

Example SPI Slave Mode (CKE = 1) ....................... 364

External Clock (All Modes Except PLL) ................... 354

Fail-Safe Clock Monitor ........................................... 273

First Start Bit Timing ................................................ 199

Full-Bridge PWM Output .......................................... 159

Half-Bridge PWM Output ......................................... 158

High/Low-Voltage Detect Characteristics ................ 351

High-Voltage Detect Operation (VDIRMAG = 1) ..... 256

I2C Bus Data ............................................................ 365

I2C Bus Start/Stop Bits ............................................ 365

PIC18F2221/2321/4221/4321 FAMILY

I2C Master Mode (7 or 10-Bit Transmission) ........... 202

I2C Master Mode (7-Bit Reception) .......................... 203

I2C Slave Mode (10-Bit Reception, SEN = 0,

ADMSK = 01001) ............................................. 187

I2C Slave Mode (10-Bit Reception, SEN = 0) .......... 188

I2C Slave Mode (10-Bit Reception, SEN = 1) .......... 193

I2C Slave Mode (10-Bit Transmission) ..................... 189

I2C Slave Mode (7-Bit Reception, SEN = 0,

ADMSK = 01011) ............................................. 185

I2C Slave Mode (7-Bit Reception, SEN = 0) ............ 184

I2C Slave Mode (7-Bit Reception, SEN = 1) ............ 192

I2C Slave Mode (7-Bit Transmission) ....................... 186

I2C Slave Mode General Call Address

Sequence (7 or 10-Bit Addressing Mode) ........ 194

I2C Stop Condition Receive or Transmit Mode ........ 204

Low-Voltage Detect Operation (VDIRMAG = 0) ...... 255

Master SSP I2C Bus Data ........................................ 367

Master SSP I2C Bus Start/Stop Bits ........................ 367

Parallel Slave Port (PIC18F4221/4321) ................... 360

Parallel Slave Port (PSP) Read ............................... 127

Parallel Slave Port (PSP) Write ............................... 127

PWM Auto-Shutdown (PRSEN = 0,

Auto-Restart Disabled) .................................... 164

PWM Auto-Shutdown (PRSEN = 1,

Auto-Restart Enabled) ..................................... 164

PWM Direction Change ........................................... 161

PWM Direction Change at Near

100% Duty Cycle ............................................. 161

PWM Output ............................................................ 150

Repeated Start Condition ......................................... 200

Reset, Watchdog Timer (WDT), Oscillator Start-up

Timer (OST), Power-up Timer (PWRT) ........... 357

Send Break Character Sequence ............................ 227

Slave Synchronization ............................................. 173

Slow Rise Time (MCLR Tied to VDD,

VDD Rise > TPWRT) ............................................ 53

SPI Mode (Master Mode) ......................................... 172

SPI Mode (Slave Mode, CKE = 0) ........................... 174

SPI Mode (Slave Mode, CKE = 1) ........................... 174

Synchronous Reception (Master Mode, SREN) ...... 230

Synchronous Transmission ...................................... 228

Synchronous Transmission (Through TXEN) .......... 229

Time-out Sequence on POR w/PLL Enabled

(MCLR Tied to VDD) ........................................... 53

Time-out Sequence on Power-up

(MCLR Not Tied to VDD, Case 1) ....................... 52

Time-out Sequence on Power-up

(MCLR Not Tied to VDD, Case 2) ....................... 52

Time-out Sequence on Power-up

(MCLR Tied to VDD, VDD Rise < TPWRT) ........... 52

Timer0 and Timer1 External Clock .......................... 358

Transition for Entry to Idle Mode ................................ 44

Transition for Entry to SEC_RUN Mode .................... 41

Transition for Entry to Sleep Mode ............................ 43

Transition for Two-Speed Start-up

(INTOSC to HSPLL) ........................................ 271

Transition for Wake from Idle to Run Mode ............... 44

Transition for Wake from Sleep (HSPLL) ................... 43

Transition from RC_RUN Mode to PRI_RUN Mode .. 42

Transition from SEC_RUN Mode to

PRI_RUN Mode (HSPLL) .................................. 41

Transition to RC_RUN Mode ..................................... 42

Timing Diagrams and Specifications ............................... 354

Capture/Compare/PWM Requirements

(All CCP Modules) ........................................... 359

CLKO and I/O Requirements ................................... 356

EUSART Synchronous Receive Requirements ....... 369

EUSART Synchronous Transmission Requirements ....

369

Example SPI Mode Requirements

(Master Mode, CKE = 0) .................................. 361

Example SPI Mode Requirements

(Master Mode, CKE = 1) .................................. 362

Example SPI Mode Requirements

(Slave Mode, CKE = 0) .................................... 363

Example SPI Mode Requirements

(Slave Mode, CKE = 1) .................................... 364

External Clock Requirements .................................. 354

I2C Bus Data Requirements (Slave Mode) .............. 366

I2C Bus Start/Stop Requirements (Slave Mode) ..... 365

Master SSP I2C Bus Data Requirements ................ 368

Master SSP I2C Bus Start/Stop Bits

Requirements .................................................. 367

Parallel Slave Port Requirements

(PIC18F4221/4321) ......................................... 360

PLL Clock ................................................................ 355

Reset, Watchdog Timer, Oscillator Start-up

Timer, Power-up Timer and

Brown-out Reset Requirements ...................... 357

Timer0 and Timer1 External Clock

Requirements .................................................. 358

Top-of-Stack Access .......................................................... 60

TRISE Register

PSPMODE Bit ......................................................... 120

TSTFSZ ........................................................................... 319

Two-Speed Start-up ................................................. 259, 271

Two-Word Instructions

Example Cases ......................................................... 64

TXSTA Register

BRGH Bit ................................................................. 215

Voltage Reference Specifications .................................... 350

Watchdog Timer (WDT) ........................................... 259, 269

Associated Registers ............................................... 270

Control Register ....................................................... 269

During Oscillator Failure .......................................... 272

Programming Considerations .................................. 269

WCOL ...................................................... 199, 200, 201, 204

WCOL Status Flag ................................... 199, 200, 201, 204

WWW Address ................................................................ 399

WWW, On-Line Support ...................................................... 8

XORLW ........................................................................... 319

XORWF ........................................................................... 320

PIC18F2221/2321/4221/4321 FAMILY

NOTES:

PIC18F2221/2321/4221/4321 FAMILY

THE MICROCHIP WEB SITE

Microchip provides online support via our WWW site at

www.microchip.com. This web site is used as a means

to make files and information easily available to

customers. Accessible by using your favorite Internet

browser, the web site contains the following

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Microchip’s customer notification service helps keep

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will receive e-mail notification whenever there are

changes, updates, revisions or errata related to a

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To register, access the Microchip web site at

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Notification and follow the registration instructions.

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Users of Microchip products can receive assistance

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Customers should contact their distributor,

representative or field application engineer (FAE) for

support. Local sales offices are also available to help

customers. A listing of sales offices and locations is

included in the back of this document.

Technical support is available through the web site

at: http://support.microchip.com

PIC18F2221/2321/4221/4321 FAMILY

READER RESPONSE

It is our intention to provide you with the best documentation possible to ensure successful use of your Microchip prod-

uct. If you wish to provide your comments on organization, clarity, subject matter, and ways in which our documentation

can better serve you, please FAX your comments to the Technical Publications Manager at (480) 792-4150.

Please list the following information, and use this outline to provide us with your comments about this document.

To: Technical Publications Manager

RE: Reader Response

Total Pages Sent ________

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Application (optional):

Would you like a reply? Y N

Device: Literature Number:

Questions:

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DS39689FPIC18F2221/2321/4221/4321 Family

1. What are the best features of this document?

2. How does this document meet your hardware and software development needs?

3. Do you find the organization of this document easy to follow? If not, why?

4. What additions to the document do you think would enhance the structure and subject?

5. What deletions from the document could be made without affecting the overall usefulness?

6. Is there any incorrect or misleading information (what and where)?

7. How would you improve this document?

PIC18F2221/2321/4221/4321 FAMILY

PIC18F2221/2321/4221/4321 PRODUCT IDENTIFICATION SYSTEM

To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.

PART NO. X/XX XXX

PatternPackageTemperature

Range

Device

Device PIC18F2221/2321(1), PIC18F4221/4321(1),

PIC18F2221/2321T(2), PIC18F4221/4321T(2);

VDD range 4.2V to 5.5V

PIC18LF2221/2321(1), PIC18LF4221/4321(1),

PIC18LF2221/2321T(2), PIC18LF4221/4321T(2);

VDD range 2.0V to 5.5V

Temperature Range I = -40°C to +85°C (Industrial)

E= -40°C to +125°C (Extended)

Package PT = TQFP (Thin Quad Flatpack)

SO = SOIC

SS = SSOP

SP = Skinny Plastic DIP

P=PDIP

ML = QFN

Pattern QTP, SQTP, Code or Special Requirements

(blank otherwise)

Examples:

a) PIC18F4321-I/P 301 = Industrial temp., PDIP

package, Extended VDD limits, QTP pattern

#301.

b) PIC18LF2321-I/SO = Industrial temp., SOIC

package, Extended VDD limits.

c) PIC18LF4321-I/P = Industrial temp., PDIP

package, normal VDD limits.

Note 1: F = Standard Voltage Range

LF = Wide Voltage Range

2: T = in tape and reel

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WORLDWIDE SALES AND SERVICE

03/26/09