qr.asm

	processor 6502
	include "vcs.h"
	include "macro.h"

	SEG
	ORG $F000

Reset
	; Clear RAM and all TIA registers
	ldx #0
	lda #0

Clear
	sta 0,x
	inx
	bne Clear

StartOfFrame
	; Start of new frame
	; Start of vertical blank processing

	lda #0
	sta VBLANK

	lda #2
	sta VSYNC

	sta WSYNC
	sta WSYNC
	sta WSYNC ; 3 scanlines of VSYNC signal

	lda #0
	sta VSYNC

	ldx #0

VerticalBlank
	sta WSYNC

	inx
	cpx #37
	bne VerticalBlank

	ldx #0 ; what line of the code are we on
	ldy #9 ; how many pixels in this line

DrawLine
	sta WSYNC	; wait till end of scanline

	lda #0
	sta PF0

	lda PFData1Left,X
	sta PF1

	lda PFData2Left,X
	sta PF2

	sleep 20

	lda PFData0Right,X
	sta PF0

	lda PFData1Right,X
	sta PF1

	lda #0
	sta PF2

	dey
	bne RedrawLine

	inx
	cpx #21
	beq StartFinish

	ldy #9

RedrawLine
	jmp DrawLine

StartFinish
	ldx #189

Finish
	sta WSYNC

	lda #0
	sta PF0
	sta PF1
	sta PF2

	inx
	cpx #192
	bne Finish

	;------------------------------------------------
 
	lda #%01000010
	sta VBLANK ; end of screen - enter blanking

	; 30 scanlines of overscan...

	ldx #0

Overscan
	sta WSYNC
	inx
	cpx #30
	bne Overscan

	jmp StartOfFrame

;------------------------------------------------------------------------------

PFData1Left
	.byte #%00000111
	.byte #%00000100
	.byte #%00000101
	.byte #%00000101
	.byte #%00000101
	.byte #%00000100
	.byte #%00000111
	.byte #%00000000
	.byte #%00000111
	.byte #%00000001
	.byte #%00000111
	.byte #%00000111
	.byte #%00000001
	.byte #%00000000
	.byte #%00000111
	.byte #%00000100
	.byte #%00000101
	.byte #%00000101
	.byte #%00000101
	.byte #%00000100
	.byte #%00000111

PFData2Left
	.byte #%00001111
	.byte #%00101000
	.byte #%01001011
	.byte #%01101011
	.byte #%10001011
	.byte #%11101000
	.byte #%10101111
	.byte #%10000000
	.byte #%01111011
	.byte #%10010010
	.byte #%01011001
	.byte #%01000010
	.byte #%10001000
	.byte #%10100000
	.byte #%00101111
	.byte #%00001000
	.byte #%11101011
	.byte #%00101011
	.byte #%10101011
	.byte #%00101000
	.byte #%11101111

PFData0Right
	.byte #%10000000
	.byte #%10110000
	.byte #%10110000
	.byte #%10010000
	.byte #%10000000
	.byte #%10110000
	.byte #%10100000
	.byte #%00110000
	.byte #%01100000
	.byte #%00000000
	.byte #%00110000
	.byte #%01000000
	.byte #%10010000
	.byte #%00000000
	.byte #%01110000
	.byte #%01000000
	.byte #%10010000
	.byte #%01000000
	.byte #%00100000
	.byte #%01010000
	.byte #%10010000

PFData1Right
	.byte #%11111100
	.byte #%00000100
	.byte #%01110100
	.byte #%01110100
	.byte #%01110100
	.byte #%00000100
	.byte #%11111100
	.byte #%00000000
	.byte #%10101000
	.byte #%01111100
	.byte #%00011000
	.byte #%01110000
	.byte #%01100100
	.byte #%11110100
	.byte #%10011000
	.byte #%01110000
	.byte #%01100000
	.byte #%11011000
	.byte #%10010000
	.byte #%11010000
	.byte #%11101000

	ORG $FFFA

InterruptVectors
	.word Reset          ; NMI
	.word Reset          ; RESET
	.word Reset          ; IRQ

END

To be fair, I was really bored.