PIC16F1933-ESLASHP datasheet(189/418 Pages) MICROCHIP

189 / 418 page

Preliminary

DS41364A-page 187

PIC16F193X/LF193X

19.3

Capture Mode

In Capture mode, the CCPRxH, CCPRxL register pair

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 (see Figure 19-1).

19.3.1

CCPX PIN CONFIGURATION

In Capture mode, the CCPx pin should be configured

as an input by setting the associated TRIS control bit.

Also, the CCPx pin function can be moved to

alternative pins using the APFCON register. Refer to

Section 6.1 “Alternate Pin Function” for more

details.

FIGURE 19-1:

CAPTURE MODE

OPERATION BLOCK

DIAGRAM

19.3.2

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.

19.3.3

SOFTWARE INTERRUPT MODE

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.

19.3.4

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 (see Example 19-1).

EXAMPLE 19-1:

CHANGING BETWEEN

CAPTURE PRESCALERS

19.3.5

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 19.1

“Capture/Compare/PWM”.

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

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