list p=16F628a
	#include "p16f628a.inc"	; De definities
	__CONFIG _CP_OFF & _BODEN_OFF & _DATA_CP_OFF & _PWRTE_ON & _WDT_OFF & _LVP_OFF & _MCLRE_ON & _INTRC_OSC_NOCLKOUT

teller		EQU	20h
sleept1		EQU	21h
sleept2		EQU	22h
tempw		EQU	23h

#define		PULSE	PORTB,0
#define		SHUTTER	PORTB,1
#define		LED	PORTB,2

	; Begin prog
	ORG 00h
		GOTO 	init

	;  Begin Interrupt
	ORG 04h
		MOVWF	tempw		; 1
		CALL	sleep993usec	; +2  +993
		NOP
		NOP
		NOP					; + 3 = 999
		CLRF	teller		; en nu 1000 usec
		
		;  1 msec is nu om, nu moeten we gaan tellen
postel	INCF	teller		; 1
		BTFSC	PULSE		; 1
		GOTO	postel		; 2 -> totaal 4 us

		BCF		INTCON, INTF	; bit 1
		MOVFW	tempw
		RETFIE

	;  Init
init	CLRF	PORTB
		BCF		STATUS, RP1
		BSF		STATUS, RP0
		CLRF	TRISB		; Portb wordt output
		BSF		PULSE		;  Uitzondering, pulse ingang

		CLRF	INTCON
		BSF		OPTION_REG, INTEDG	; rising edge
		BSF		INTCON, INTE	; enable INT interrupt
		BSF		INTCON, GIE	; enable alle interrupts
		BCF		STATUS, RP0
		CLRF	teller;
begin	MOVFW	teller
		BSF		PORTB,3
		BTFSC	teller,7
		GOTO	aan
		GOTO	uit
aan		BSF		LED
		BSF		SHUTTER
		GOTO	begin
uit		BCF		LED
		BCF		SHUTTER
		GOTO	begin

sleep993usec
		MOVLW	d'198'		; 1
		MOVWF	sleept1		; 1
sleep993in	
		NOP			; \
		NOP			;  | 5 msec 
		DECFSZ	sleept1, 1	;  |
		GOTO	sleep993in	; /
		RETURN			;
	END