© 2004 Microchip Technology Inc. DS70060C-page 13-7
Section 13. Input Capture
Input Capture
13
Example 13-1: Prescaled Capture Code Example
; The following code example will set the Input Capture 1 module
; for interrupts on every second capture event, capture on every
; fourth rising edge and select Timer 2 as the time-base. This
; code example clears ICxCON to avoid unexpected interrupts.
BSET IPC0, #IC1IP0 ; Setup Input Capture 1 interrupt for
BCLR IPC0, #IC1IP1 ; desired priority level
BCLR IPC0, #IC1IP2 ; (this example assigns level 1 priority)
BCLR IFS0, #IC1IF ; Clear the IC1 interrupt status flag
BSET IEC0, #IC1IE ; Enable IC1 interrupts
CLR IC1CON ; Turn off Input Capture 1 Module.
MOV #0x00A2, w0 ; Load the working register with the new
MOV w0, IC1CON ; prescaler mode and write to IC1CON
MOV #IC1BUF, w0 ; Create capture data fetch pointer
MOV #TEMP_BUFF, w1 ; Create data storage pointer
; Assumes TEMP_BUFF is already defined
; The following code shows how to read the capture buffer when
; an interrupt is generated. W0 contains the capture buffer address.
; Example code for Input Capture 1 ISR:
__IC1Interrupt:
BCLR IFS0, #IC1IF ; Reset respective interrupt flag
MOV [w0++], [w1++] ; Read and save off first capture entry
MOV [w0], [w1] ; Read and save off second capture entry
; Remaining user code here
RETFIE ; Return from ISR
Note: It is recommended that the user turn off the capture module (i.e., clear ICM<2:0>
(ICxCON<2:0>)) before switching to a new mode. If the user switches to a new
Capture mode, the prescaler counter is not cleared. Therefore, it is possible that the
first capture event and its associated interrupt is generated due to a non-zero
prescaler counter (at the time of switching modes).
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