PIC16F722-ESLASHML datasheet(137/302 Pages) MICROCHIP

137 / 302 page

DS41341E-page 137

PIC16F72X/PIC16LF72X

15.1

Capture Mode

In Capture mode, CCPRxH:CCPRxL captures the

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

on pin CCPx. An event is defined as one of the

following and is configured by the CCPxM<3:0> bits of

the CCPxCON register:

• Every falling edge

• Every rising edge

• Every 4th rising edge

• Every 16th rising edge

When a capture is made, the Interrupt Request Flag bit

CCPxIF of the PIRx register is set. The interrupt flag

must be cleared in software. If another capture occurs

before the value in the CCPRxH, CCPRxL register pair

is read, the old captured value is overwritten by the new

captured value (refer to Figure 15-1).

15.1.1

CCPx PIN CONFIGURATION

In Capture mode, the CCPx pin should be configured

as an input by setting the associated TRIS control bit.

Either RC1 or RB3 can be selected as the CCP2 pin.

Refer to Section 6.1 “Alternate Pin Function” for

more information.

FIGURE 15-1:

CAPTURE MODE

OPERATION BLOCK

DIAGRAM

15.1.2

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 or when

Timer1 is clocked at FOSC, the capture operation may

not work.

15.1.3

SOFTWARE INTERRUPT

When the Capture mode is changed, a false capture

interrupt may be generated. The user should keep the

CCPxIE interrupt enable bit of the PIEx register clear to

avoid false interrupts. Additionally, the user should

clear the CCPxIF interrupt flag bit of the PIRx register

following any change in operating mode.

15.1.4

CCP PRESCALER

There are four prescaler settings specified by the

CCPxM<3:0> bits of the CCPxCON register. Whenever

the CCP module is turned off, or the CCP module is not

in Capture mode, the prescaler counter is cleared. Any

Reset will clear the prescaler counter.

Switching from one capture prescaler to another does not

clear the prescaler and may generate a false interrupt. To

avoid this unexpected operation, turn the module off by

clearing the CCPxCON register before changing the

prescaler (refer to Example 15-1).

EXAMPLE 15-1:

CHANGING BETWEEN

CAPTURE PRESCALERS

15.1.5

CAPTURE DURING SLEEP

Capture mode depends upon the Timer1 module for

proper operation. There are two options for driving the

Timer1 module in Capture mode. It can be driven by

the instruction clock (FOSC/4), or by an external clock

source.

If Timer1 is clocked by FOSC/4, then Timer1 will not

increment during Sleep. When the device wakes from

Sleep, Timer1 will continue from its previous state.

If Timer1 is clocked by an external clock source, then

Capture mode will operate as defined in Section 15.1

“Capture Mode”.

Note:

If the CCPx pin is configured as an output,

a write to the port can cause a capture

condition.

CCPRxH

CCPRxL

TMR1H

TMR1L

Set Flag bit CCPxIF

(PIRx register)

Capture

Enable

CCPxCON<3:0>

Prescaler

÷ 1, 4, 16

and

Edge Detect

CCPx

System Clock (FOSC)

Note:

Clocking Timer1 from the system clock

(FOSC) should not be used in Capture

Mode. In order for Capture Mode to

recognize the trigger event on the CCPx

pin, Timer1 must be clocked from the

Instruction Clock (FOSC/4) or from an

external clock source.

BANKSEL CCP1CON

;Set Bank bits to point

;to CCP1CON

CLRF

CCP1CON

;Turn CCP module off

MOVLW

NEW_CAPT_PS ;Load the W reg with

; the new prescaler

; move value and CCP ON

MOVWF

CCP1CON

;Load CCP1CON with this

; value

PIC16F722-E/ML Datasheet(PDF) 137 Page - Microchip Technology

PIC16F722-E/ML Datasheet(HTML) 137 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL