PIC16F684-I/SLG Microchip, PIC16F684-I/SLG Datasheet - Page 78

• Manufacturer Part Number: PIC16F684-I/SLG
• Description: pic, flash, Microcontrollers, Microprocessors, Semiconductors and Actives, ic, mcu
• Manufacturer: Microchip

PIC16F684
11.1
In Capture mode, CCPR1H:CCPR1L captures the
16-bit value of the TMR1 register when an event occurs
on pin RC5/CCP1/P1A. An event is defined as one of
the following and is configured by CCP1CON<3:0>:
• Every falling edge
• Every rising edge
• Every 4th rising edge
• Every 16th rising edge
When a capture is made, the interrupt request flag bit,
CCP1IF (PIR1<5>), is set. The interrupt flag must be
cleared in software. If another capture occurs before
the value in register CCPR1 is read, the old captured
value is overwritten by the new captured value.
11.1.1
In Capture mode, the RC5/CCP1/P1A pin should be
configured as an input by setting the TRISC<5> bit.
FIGURE 11-1:
11.1.2
Timer1 must be running in Timer mode or Synchro-
nized Counter mode for the ECCP module to use the
capture feature. In Asynchronous Counter mode, the
capture operation may not work.
11.1.3
When the Capture mode is changed, a false capture
interrupt may be generated. The user should keep bit
CCP1IE (PIE1<5>) clear to avoid false interrupts and
should clear the flag bit CCP1IF (PIR1<5>) following
any such change in operating mode.
DS41202C-page 76
RC5/CCP1/P1A
pin
Note:
Capture Mode
Edge Detect
Q’s
CCP1 PIN CONFIGURATION
If the RC5/CCP1/P1A pin is configured as
an output, a write to the port can cause a
capture condition.
Prescaler
TIMER1 MODE SELECTION
SOFTWARE INTERRUPT
1, 4, 16
and
CCP1CON<3:0>
Set Flag bit CCP1IF
CAPTURE MODE
OPERATION BLOCK
DIAGRAM
(PIR1<5>)
Capture
Enable
CCPR1H
TMR1H
CCPR1L
TMR1L
Preliminary
11.1.4
There are four prescaler settings specified by bits
CCP1M<3:0> (CCP1CON<3:0>). Whenever the ECCP
module is turned off, or the ECCP 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 may
generate an interrupt. Also, the prescaler counter will
not be cleared; therefore, the first capture may be from
a non-zero prescaler. Example 11-1 shows the recom-
mended method for switching between capture
prescalers. This example also clears the prescaler
counter and will not generate the “false” interrupt.
EXAMPLE 11-1:
CLRF
MOVLW
MOVWF
CCP1CON
NEW_CAPT_PS ;Load the W reg with
CCP1CON
ECCP PRESCALER
CHANGING BETWEEN
CAPTURE PRESCALERS
;Turn ECCP module off
;the new prescaler
;move value and ECCP ON
;Load CCP1CON with this
;value
 2004 Microchip Technology Inc.