mirror of
https://gitlab.com/xCrystal/pokecrystal-board.git
synced 2024-11-16 11:27:33 -08:00
540 lines
7.1 KiB
NASM
540 lines
7.1 KiB
NASM
; VBlank is the interrupt responsible for updating VRAM.
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; In Pokemon Crystal, VBlank has been hijacked to act as the
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; main loop. After time-sensitive graphics operations have been
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; performed, joypad input and sound functions are executed.
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; This prevents the display and audio output from lagging.
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push af
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push bc
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push de
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push hl
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; get vblank type
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ld a, [$ff9e]
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and $7
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; get fn pointer
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ld e, a
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ld d, $0
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ld hl, .VBlanks
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add hl, de
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add hl, de
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ld a, [hli]
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ld h, [hl]
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ld l, a
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; down to business
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call JpHl
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; since this is called once per frame
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call GameTimer
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pop hl
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pop de
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pop bc
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pop af
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reti
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; 2a1
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.VBlanks ; 2a1
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dw VBlank0 ; 0
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dw VBlank1 ; 1
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dw VBlank2 ; 2
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dw VBlank3 ; 3
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dw VBlank4 ; 4
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dw VBlank5 ; 5
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dw VBlank6 ; 6
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dw VBlank0 ; 7
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; 2b1
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VBlank0: ; 2b1
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; normal operation
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; rng
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; scx, scy, wy, wx
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; bg map buffer
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; palettes
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; dma transfer
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; bg map
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; tiles
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; oam
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; joypad
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; sound
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; inc frame counter
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ld hl, $ff9b
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inc [hl]
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; advance rng
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ld a, [rDIV]
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ld b, a
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ld a, [hRandomAdd]
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adc b
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ld [hRandomAdd], a
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ld a, [rDIV]
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ld b, a
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ld a, [hRandomSub]
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sbc b
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ld [hRandomSub], a
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; save bank
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ld a, [hROMBank] ; current bank
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ld [$ff8a], a
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; scroll x
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ld a, [hSCX]
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ld [rSCX], a
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; scroll y
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ld a, [hSCY]
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ld [rSCY], a
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; window y
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ld a, [hWY]
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ld [rWY], a
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; window x + 7
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ld a, [hWX]
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ld [rWX], a
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; some time management is in order
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; only have time for one of these during vblank
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; bg map buffer has priority
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call UpdateBGMapBuffer
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jr c, .doneframeaction
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; then pals
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call UpdatePalsIfCGB
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jr c, .doneframeaction
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; dma transfer
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call DMATransfer
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jr c, .doneframeaction
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; bg map
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call UpdateBGMap
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; these have their own timing checks
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call SafeLoadTiles
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call SafeLoadTiles2
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call SafeTileAnimation
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.doneframeaction
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; oam update off?
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ld a, [hOAMUpdate]
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and a
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jr nz, .vblankoccurred
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; update oam by dma transfer
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call hPushOAM
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; 403f:
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; ld a, $c4
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; ld [rDMA], a
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; ld a, $28
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; .loop
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; dec a
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; jr nz, .loop
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; ret
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; vblank-sensitive operations are done
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.vblankoccurred
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; tell other fns vblank happened
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xor a
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ld [VBlankOccurred], a
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; dec OverworldDelay until 0
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ld a, [OverworldDelay]
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and a
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jr z, .textdelay
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dec a
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ld [OverworldDelay], a
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.textdelay
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; dec text delay counter until 0
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ld a, [TextDelayFrames]
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and a
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jr z, .joypad
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dec a
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ld [TextDelayFrames], a
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.joypad
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call Joypad
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; update sound
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ld a, BANK(UpdateSound)
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rst Bankswitch ; bankswitch
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call UpdateSound
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ld a, [$ff8a]
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rst Bankswitch ; restore bank
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;
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ld a, [hSeconds]
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ld [$ffe3], a
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ret
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; 325
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VBlank2: ; 325
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; sound only
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; save bank
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ld a, [hROMBank]
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ld [$ff8a], a
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; update sound
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ld a, BANK(UpdateSound)
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rst Bankswitch ; bankswitch
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call UpdateSound
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; restore bank
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ld a, [$ff8a]
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rst Bankswitch
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; tell other fns vblank happened
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xor a
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ld [VBlankOccurred], a
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ret
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; 337
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VBlank1: ; 337
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; scx, scy
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; palettes
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; bg map
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; tiles
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; oam
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; sound / lcd stat
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; save bank
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ld a, [hROMBank]
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ld [$ff8a], a
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; scroll x
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ld a, [hSCX]
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ld [rSCX], a
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; scroll y
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ld a, [hSCY]
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ld [rSCY], a
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; time-sensitive fns
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call UpdatePals
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jr c, .vblankoccurred
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; these have their own timing checks
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call UpdateBGMap
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call LoadTiles
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; update oam by dma transfer
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call hPushOAM
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; 403f:
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; ld a, $c4
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; ld [rDMA], a
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; ld a, $28
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; .loop
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; dec a
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; jr nz, .loop
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; ret
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.vblankoccurred
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; tell other fns vblank happened
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xor a
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ld [VBlankOccurred], a
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; get requested ints
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ld a, [rIF]
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ld b, a
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; discard requested ints
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xor a
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ld [rIF], a
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; enable lcd stat
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ld a, %10 ; lcd stat
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ld [rIE], a
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; rerequest serial int if applicable (still disabled)
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; request lcd stat
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ld a, b
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and %1000 ; serial
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or %10 ; lcd stat
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ld [rIF], a
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ei
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; update sound
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ld a, BANK(UpdateSound)
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rst Bankswitch ; bankswitch
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call UpdateSound
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; restore bank
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ld a, [$ff8a]
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rst Bankswitch
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di
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; get requested ints
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ld a, [rIF]
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ld b, a
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; discard requested ints
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xor a
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ld [rIF], a
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; enable ints besides joypad
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ld a, %1111 ; serial timer lcdstat vblank
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ld [rIE], a
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; rerequest ints
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ld a, b
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ld [rIF], a
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ret
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; 37f
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UpdatePals: ; 37f
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; update pals for either dmg or cgb
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; check cgb
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ld a, [hCGB]
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and a
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jp nz, UpdateCGBPals
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; update gb pals
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ld a, [$cfc7]
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ld [rBGP], a
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ld a, [$cfc8]
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ld [rOBP0], a
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ld a, [$cfc9]
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ld [rOBP1], a
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and a
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ret
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; 396
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VBlank3: ; 396
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; scx, scy
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; palettes
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; bg map
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; tiles
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; oam
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; sound / lcd stat
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; save bank
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ld a, [hROMBank]
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ld [$ff8a], a
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; scroll x
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ld a, [hSCX]
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ld [rSCX], a
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; scroll y
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ld a, [hSCY]
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ld [rSCY], a
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; any pals to update?
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ld a, [hCGBPalUpdate]
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and a
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call nz, ForceUpdateCGBPals
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jr c, .vblankoccurred
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; else
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call UpdateBGMap
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call LoadTiles
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; update oam by dma transfer
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call hPushOAM
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; 403f:
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; ld a, $c4 ; Sprites / $100
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; ld [rDMA], a
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; ld a, $28
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; .loop
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; dec a
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; jr nz, .loop
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; ret
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.vblankoccurred
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; tell other fns vblank happened
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xor a
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ld [VBlankOccurred], a
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; save int flag
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ld a, [rIF]
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push af
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; reset ints
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xor a
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ld [rIF], a
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; force lcdstat int during sound update
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ld a, %10 ; lcd stat
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ld [rIE], a
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ld [rIF], a
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ei
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; update sound
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ld a, BANK(UpdateSound)
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rst Bankswitch ; bankswitch
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call UpdateSound
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; restore bank
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ld a, [$ff8a]
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rst Bankswitch
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di
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; request lcdstat
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ld a, [rIF]
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ld b, a
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; and any other ints
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pop af
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or b
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ld b, a
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; reset ints
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xor a
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ld [rIF], a
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; enable ints besides joypad
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ld a, %1111 ; serial timer lcdstat vblank
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ld [rIE], a
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; request ints
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ld a, b
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ld [rIF], a
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ret
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; 3df
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VBlank4: ; 3df
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; bg map
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; tiles
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; oam
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; joypad
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; serial
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; sound
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; save bank
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ld a, [hROMBank]
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ld [$ff8a], a
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call UpdateBGMap
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call SafeLoadTiles
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; update oam by dma transfer
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call hPushOAM
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; 403f:
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; ld a, $c4
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; ld [rDMA], a
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; ld a, $28
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; .loop
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; dec a
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; jr nz, .loop
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; ret
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; update joypad
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call Joypad
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; tell other fns vblank happened
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xor a
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ld [VBlankOccurred], a
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; handshake
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call AskSerial
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; update sound
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ld a, BANK(UpdateSound)
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rst Bankswitch ; bankswitch
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call UpdateSound
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; restore bank
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ld a, [$ff8a]
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rst Bankswitch
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ret
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; 400
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VBlank5: ; 400
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; scx
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; palettes
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; bg map
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; tiles
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; joypad
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;
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; save bank
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ld a, [hROMBank]
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ld [$ff8a], a
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; scroll x
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ld a, [hSCX]
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ld [rSCX], a
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; if we can update pals, skip this part
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call UpdatePalsIfCGB
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jr c, .vblankoccurred
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call UpdateBGMap
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call SafeLoadTiles
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.vblankoccurred
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; tell other fns vblank happened
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xor a
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ld [VBlankOccurred], a
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; joypad
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call Joypad
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; discard requested ints
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xor a
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ld [rIF], a
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; enable lcd stat
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ld a, %10 ; lcd stat
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ld [rIE], a
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; request lcd stat
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ld [rIF], a
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ei
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; update sound
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ld a, BANK(UpdateSound)
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rst Bankswitch ; bankswitch
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call UpdateSound
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; restore bank
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ld a, [$ff8a]
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rst Bankswitch
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di
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; discard requested ints
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xor a
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ld [rIF], a
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; enable ints besides joypad
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ld a, %1111 ; serial timer lcdstat vblank
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ld [rIE], a
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ret
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; 436
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VBlank6: ; 436
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; palettes
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; tiles
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; dma transfer
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; sound
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; save bank
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ld a, [hROMBank]
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ld [$ff8a], a
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; inc frame counter
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ld hl, $ff9b
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inc [hl]
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call UpdateCGBPals
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jr c, .vblankoccurred
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call SafeLoadTiles
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call SafeLoadTiles2
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call DMATransfer
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.vblankoccurred
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; tell other fns vblank happened
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xor a
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ld [VBlankOccurred], a
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; update sound
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ld a, BANK(UpdateSound)
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rst Bankswitch ; bankswitch
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call UpdateSound
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; restore bank
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ld a, [$ff8a]
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rst Bankswitch
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ret
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; 45a
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