#include 	"c:\miniide\hcs12.inc"

		org	$1000
count		ds.b	1		; reserve one byte for counter
		org	$1500
		lds	#$3C00		; initialize stack pointer
		movb	#$FF,ddrb	; configure port B for output
		clr	count		; initialize count to 0
		movb	count,portb	; output count to portb
		movb	#$C0,irqcr	; enable IRQ interrupt and edge triggered
		cli			;	"
forever		nop			; wait for interrupt to occur
		bra	forever		;	"

irq_ISR		inc	count
		movb	count,portb
		rti
		org     $EFF2
		fdb	irq_ISR
		end