****************************************************
;
; Example program for testing the Cross64 assembler
;
; Expanding screen borders vertcally.
; After expansion a sprite placed under the top or
; bottom screen border will be visible.
;
****************************************************
	ORG $C000

* Initialize the interrupt.
START	SEI
	LDA #>IRQ	; interrupt vector
	STA $FFFE
	LDA #<IRQ
	STA $FFFF
	LDA #$7F	; disable IRQ interrupt
	STA $DC0D
	LDA #1		; enable raster interrupt
	STA $D01A
	LDA #$F8	; interrupt at $F8
	STA $D012
	LDA #$1B
	STA $D011
	LDA $DC0D
	CLI

L001	JMP L001

* Expanding top & bottom borders.
* Interrupt at raster line $F8.
;IRQ	STA REMA+1	; store registers
;	STX REMX+1	; note that arithmetic operations are not implemented
;	STY REMY+1	;   in Cross64 yet...
IRQ	STA REMA	; store registers
	STX REMX
	STY REMY
	LDA $D019	; acknowledge the interrupt
	STA $D019
	LDA #$13	; shrink screen vertically
	STA $D011	; (24 lines)
	LDA #$FC	; wait for raster line $FC
L002	CMP $D012
	BNE L002
	LDA #$1B	; restore screen height
	STA $D011	; to normal (25 lines)
REMA	LDA #0
REMX	LDX #0
REMY	LDY #0
	RTI