PIC16C712T-04/SO View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC16C712T-04/SO

8-Bit CMOS Microcontrollers with A/D Converter and Capture/Compare/PWM

Microchip Technology 

PIC16C712/716

7.1 Capture Mode

In Capture mode, CCPR1H:CCPR1L captures the

16-bit value of the TMR1 register when an event occurs

on pin RB3/CCP1. An event is defined as:

• every falling edge

• every rising edge

• every 4th rising edge

• every 16th rising edge

An event is selected by control bits CCP1M3:CCP1M0

(CCP1CON<3:0>). When a capture is made, the inter-

rupt request flag bit CCP1IF (PIR1<2>) is set. It must

be cleared in software. If another capture occurs before

the value in register CCPR1 is read, the old captured

value will be lost.

FIGURE 7-3: CAPTURE MODE OPERATION

BLOCK DIAGRAM

RB3/CCP1

Pin

Set flag bit CCP1IF

Prescaler

(PIR1<2>)

÷ 1, 4, 16

CCPR1H

and

edge detect

Capture

Enable

CCP1CON<3:0>

Q’s

TMR1H

CCPR1L

TMR1L

7.1.1 CCP PIN CONFIGURATION

In Capture mode, the CCP output must be disabled by

setting the TRISCCP<2> bit.

Note:

If the RB3/CCP1 is configured as an output

by clearing the TRISCCP<2> bit, a write to

the DCCP bit can cause a capture condi-

tion.

7.1.2 TIMER1 MODE SELECTION

Timer1 must be running in timer mode or synchronized

counter mode for the CCP module to use the capture

feature. In asynchronous counter mode, the capture

operation may not work.

7.1.3 SOFTWARE INTERRUPT

When the Capture mode is changed, a false capture

interrupt may be generated. The user should keep bit

CCP1IE (PIE1<2>) clear to avoid false interrupts and

should clear the flag bit CCP1IF following any such

change in operating mode.

7.1.4 CCP PRESCALER

There are four prescaler settings, specified by bits

CCP1M3:CCP1M0. Whenever the CCP module is

turned off, or the CCP module is not in capture mode,

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 7-1 shows the recom-

mended method for switching between capture pres-

calers. This example also clears the prescaler counter

and will not generate the “false” interrupt.

EXAMPLE 7-1: CHANGING BETWEEN

CAPTURE PRESCALERS

CLRF CCP1CON

;Turn CCP module off

MOVLW NEW_CAPT_PS ;Load the W reg with

; the new prescaler

; mode value and CCP ON

MOVWF CCP1CON

;Load CCP1CON with this

; value

DS41106A-page 40

Preliminary

© 1999 Microchip Technology Inc.

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