putscreen:
; Wait for vblank
-.stat: ld a, [$FF41]
- ld [$FF51], a
- and $03 ; mode
- cp $01 ; VBLANK
- jr nz, .stat
+ call .vblwait
ld hl, $8000 ; Copy two tiles.
ld a, $AA
ld [hli], a
ld hl, $9800
+.vloop: call .vblwait
+ ld c, $40
.loop: ld a, $01
ld [hli], a
xor a
ld [hli], a
ld a, h
cp $9C
- jp nz,.loop
+ ret z
+ dec c
+ xor a
+ cp c
+ jr nz,.loop
+ jr .vloop
+
+.vblwait:
+.stat1: ld a, [$FF41] ; STAT
+ and $03
+ cp $00
+ jp nz, .stat1
+.stat2: ld a, [$FF41]
+ and $03
+ cp $01
+ jr nz, .stat2
ret
vbl:
xor a
ld [$FF0F], a
- ld c, $42 ; SCY
- ld a, [c]
- inc a
- ld [c], a
+ ld a, [$FF51]
+ ld b, a
+ and $80
+ cp $80
+ jr nz, .nothing
+ ld c, $0
+
+ ld a, b
+ and $1
+ cp c
+ call nz, .scyup
- ld c, $43 ; SCX
- ld a, [c]
- inc a
- ld [c], a
+ ld a, b
+ and $2
+ cp c
+ call nz, .scydown
+
+ ld a, b
+ and $4
+ cp c
+ call nz, .scxup
+
+ ld a, b
+ and $8
+ cp c
+ call nz, .scxdown
+.nothing:
POP HL
POP DE
POP BC
RETI
+.scyup: ld hl, $FF42
+ inc [hl]
+ ret
+
+.scydown: ld hl, $FF42
+ dec [hl]
+ ret
+
+.scxup: ld hl, $FF43
+ inc [hl]
+ ret
+
+.scxdown: ld hl, $FF43
+ dec [hl]
+ ret
+
+
lcdc:
PUSH AF
PUSH BC