DarrelsExample

' PIC18F242 @20MHz
DEFINE OSC 20
DEFINE DEBUG_REG PORTC
DEFINE DEBUG_BIT 6 
DEFINE DEBUG_BAUD 115200
DEFINE DEBUG_MODE 0 ' 1 = inverted, 0 = true

OverFlows  VAR BYTE ' Timer1 overflow total
Remainder  VAR WORD ' Remaining Timer1 ticks after falling edge capture

INCLUDE "DT_INTS-18.bas"       ; Base Interrupt System
INCLUDE "ReEnterPBP-18.bas"    ; Include if using PBP interrupts

;----[High Priority Interrupts]----------------------------------------
ASM
INT_LIST  macro    ; IntSource,   Label,   Type, ResetFlag?
        INT_Handler   CCP1_INT,  _Capture,  PBP,  yes
        INT_Handler   TMR1_INT,  _Timer1,   PBP,  yes
    endm
    INT_CREATE               ; Creates the High Priority interrupt processor
ENDASM

CCP1CON = %00000101  ' Capture mode, capture on rising edge
T1CON = 0            ' TMR1 prescale=1, clock=Fosc/4, TMR1=off (200nS per count @20MHz)
@    INT_ENABLE  CCP1_INT    ; enable Capture interrupts

Main:    
    IF T1CON.0 = 0 THEN ' If done, show result
      DEBUG "Timer Overflows = ",DEC OverFlows
      DEBUG " Remaining ticks = ",dec Remainder,13,10
    ENDIF
    PAUSE 2000
    @    INT_ENABLE  CCP1_INT     ; Start new capture
    GOTO Main

'---[CCP1 - interrupt handler]------------------------------------------
Capture:
   IF CCP1CON = %00000101 THEN     ' If rising edge capture then
     TMR1L = 0                     ' Clear Timer1 counts
     TMR1H = 0
     T1CON.0 = 1                   ' Turn Timer1 on at rising edge capture
     OverFlows = 0                 ' Clear over flow counts
     Remainder = 0                 ' Clear remainder
     CCP1CON = %00000100           ; Switch to falling edge capture
     PIR1.0 = 0                    ; Clear Timer1 overflow flag before enable
     @    INT_ENABLE  TMR1_INT     ; Enable Timer 1 Interrupts 
     GOTO OVER_CCP                 ; Done, exit
   ENDIF

   IF CCP1CON = %00000100 THEN     ; If falling edge capture then
     T1CON.0 = 0                   ; Stop Timer1
     CCP1CON = %00000101           ; Switch back to rising edge capture
     @    INT_DISABLE  TMR1_INT    ; Disable Timer 1 Interrupts
     @    INT_DISABLE  CCP1_INT    ; Disable CCP1 Interrupts
     Remainder.LowByte = TMR1L     ; Get remaining Timer1 counts on falling edge
     Remainder.HighByte = TMR1H
   ENDIF
OVER_CCP:
@ INT_RETURN

'---[TMR1 - interrupt handler]---------------------------------------------
Timer1:
    OverFlows = OverFlows + 1
@ INT_RETURN

     END