PIC16F877ATISLASHML datasheet(68/234 Pages) MICROCHIP

68 / 234 page

PIC16F87XA

DS39582B-page 66

 2003 Microchip Technology Inc.

8.2

Compare Mode

In Compare mode, the 16-bit CCPR1 register value is

constantly compared against the TMR1 register pair

value. When a match occurs, the RC2/CCP1 pin is:

• Driven high

•Driven low

• Remains unchanged

The action on the pin is based on the value of control

bits, CCP1M3:CCP1M0 (CCP1CON<3:0>). At the

same time, interrupt flag bit CCP1IF is set.

FIGURE 8-2:

COMPARE MODE

OPERATION BLOCK

DIAGRAM

8.2.1

CCP PIN CONFIGURATION

The user must configure the RC2/CCP1 pin as an

output by clearing the TRISC<2> bit.

8.2.2

TIMER1 MODE SELECTION

Timer1 must be running in Timer mode, or Synchro-

nized Counter mode, if the CCP module is using the

compare feature. In Asynchronous Counter mode, the

compare operation may not work.

8.2.3

SOFTWARE INTERRUPT MODE

When Generate Software Interrupt mode is chosen, the

CCP1 pin is not affected. The CCPIF bit is set, causing

a CCP interrupt (if enabled).

8.2.4

SPECIAL EVENT TRIGGER

In this mode, an internal hardware trigger is generated

which may be used to initiate an action.

The special event trigger output of CCP1 resets the

TMR1 register pair. This allows the CCPR1 register to

effectively be a 16-bit programmable period register for

Timer1.

The special event trigger output of CCP2 resets the

TMR1 register pair and starts an A/D conversion (if the

A/D module is enabled).

Note:

Clearing the CCP1CON register will force

the RC2/CCP1 compare output latch to

the default low level. This is not the

PORTC I/O data latch.

CCPR1H CCPR1L

TMR1H

TMR1L

Comparator

Output

Logic

Special Event Trigger

Set Flag bit CCP1IF

(PIR1<2>)

Match

RC2/CCP1

TRISC<2>

CCP1CON<3:0>

Mode Select

Output Enable

Special event trigger will:

reset Timer1, but not set interrupt flag bit TMR1IF (PIR1<0>)

and set bit GO/DONE (ADCON0<2>).

Note:

The special event trigger from the CCP1

and CCP2 modules will not set interrupt

flag bit TMR1IF (PIR1<0>).

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