;
; A small program to demonstrate how to sync to the raster counter.
; This code assumes that there are 63 cycles per raster line.
;
; Michiel Boland 2 Nov 2004

rc	=	$d012	; raster counter
ec	=	$d020	; exterior color

	.org	$c000 - 2

	.word	start

start:	lda	rc			; Wait for next line.
l0:	cmp	rc			; We are now off by at most 7 cycles.
	beq	l0
	jsr	delay			; Delay 50 cycles
	lda	rc
	cmp	rc			; If rc hasn't increased yet, add
	bne	l1			; 4 more cycles.
	bit	0
	nop
l1:	jsr	delay
	lda	rc
	cmp	rc			; Add 2 cycles if needed.
	beq	l2
l2:	beq	l3
l3:	jsr	delay
	lda	rc
	cmp	rc
	beq	l4			; Add 1 cycle if needed.
l4:	inc	ec			; Sync complete.
	jmp	start

delay:	ldy	#7
l5:	dey
	bne	l5
	nop
	rts