ref: d461689704c05c878ef094e34dd7b6fd6fb4b445
dir: /home/vblank.asm/
; VBlank is the interrupt responsible for updating VRAM. ; In Pokemon Crystal, VBlank has been hijacked to act as the ; main loop. After time-sensitive graphics operations have been ; performed, joypad input and sound functions are executed. ; This prevents the display and audio output from lagging. VBlank: ; 283 push af push bc push de push hl ; get vblank type ld a, [$ff9e] and $7 ; get fn pointer ld e, a ld d, $0 ld hl, .VBlanks add hl, de add hl, de ld a, [hli] ld h, [hl] ld l, a ; down to business call _hl_ ; since this is called once per frame call GameTimer pop hl pop de pop bc pop af reti ; 2a1 .VBlanks ; 2a1 dw VBlank0 ; 0 dw VBlank1 ; 1 dw VBlank2 ; 2 dw VBlank3 ; 3 dw VBlank4 ; 4 dw VBlank5 ; 5 dw VBlank6 ; 6 dw VBlank0 ; 7 ; 2b1 VBlank0: ; 2b1 ; normal operation ; rng ; scx, scy, wy, wx ; bg map buffer ; palettes ; dma transfer ; bg map ; tiles ; oam ; joypad ; sound ; inc frame counter ld hl, $ff9b inc [hl] ; advance rng ld a, [rDIV] ld b, a ld a, [hRandomAdd] adc b ld [hRandomAdd], a ld a, [rDIV] ld b, a ld a, [hRandomSub] sbc b ld [hRandomSub], a ; save bank ld a, [hROMBank] ; current bank ld [$ff8a], a ; scroll x ld a, [hSCX] ld [rSCX], a ; scroll y ld a, [hSCY] ld [rSCY], a ; window y ld a, [hWY] ld [rWY], a ; window x + 7 ld a, [hWX] ld [rWX], a ; some time management is in order ; only have time for one of these during vblank ; bg map buffer has priority call UpdateBGMapBuffer jr c, .doneframeaction ; then pals call UpdatePalsIfCGB jr c, .doneframeaction ; dma transfer call DMATransfer jr c, .doneframeaction ; bg map call UpdateBGMap ; these have their own timing checks call Serve2bppRequest call Serve1bppRequest call AnimateTileset .doneframeaction ; oam update off? ld a, [hOAMUpdate] and a jr nz, .vblankoccurred ; update oam by dma transfer call hPushOAM ; @PushOAM: ; ld a, Sprites >> 8 ; ld [rDMA], a ; ld a, $28 ; .loop ; dec a ; jr nz, .loop ; ret ; vblank-sensitive operations are done .vblankoccurred ; tell other fns vblank happened xor a ld [VBlankOccurred], a ; dec OverworldDelay until 0 ld a, [OverworldDelay] and a jr z, .textdelay dec a ld [OverworldDelay], a .textdelay ; dec text delay counter until 0 ld a, [TextDelayFrames] and a jr z, .joypad dec a ld [TextDelayFrames], a .joypad call Joypad ; update sound ld a, BANK(_UpdateSound) rst Bankswitch ; bankswitch call _UpdateSound ld a, [$ff8a] rst Bankswitch ; restore bank ; ld a, [hSeconds] ld [$ffe3], a ret ; 325 VBlank2: ; 325 ; sound only ; save bank ld a, [hROMBank] ld [$ff8a], a ; update sound ld a, BANK(_UpdateSound) rst Bankswitch ; bankswitch call _UpdateSound ; restore bank ld a, [$ff8a] rst Bankswitch ; tell other fns vblank happened xor a ld [VBlankOccurred], a ret ; 337 VBlank1: ; 337 ; scx, scy ; palettes ; bg map ; tiles ; oam ; sound / lcd stat ; save bank ld a, [hROMBank] ld [$ff8a], a ; scroll x ld a, [hSCX] ld [rSCX], a ; scroll y ld a, [hSCY] ld [rSCY], a ; time-sensitive fns call UpdatePals jr c, .vblankoccurred ; these have their own timing checks call UpdateBGMap call Serve2bppRequest@VBlank ; update oam by dma transfer call hPushOAM ; @PushOAM: ; ld a, Sprites >> 8 ; ld [rDMA], a ; ld a, $28 ; .loop ; dec a ; jr nz, .loop ; ret .vblankoccurred ; tell other fns vblank happened xor a ld [VBlankOccurred], a ; get requested ints ld a, [rIF] ld b, a ; discard requested ints xor a ld [rIF], a ; enable lcd stat ld a, %10 ; lcd stat ld [rIE], a ; rerequest serial int if applicable (still disabled) ; request lcd stat ld a, b and %1000 ; serial or %10 ; lcd stat ld [rIF], a ei ; update sound ld a, BANK(_UpdateSound) rst Bankswitch ; bankswitch call _UpdateSound ; restore bank ld a, [$ff8a] rst Bankswitch di ; get requested ints ld a, [rIF] ld b, a ; discard requested ints xor a ld [rIF], a ; enable ints besides joypad ld a, %1111 ; serial timer lcdstat vblank ld [rIE], a ; rerequest ints ld a, b ld [rIF], a ret ; 37f UpdatePals: ; 37f ; update pals for either dmg or cgb ; check cgb ld a, [hCGB] and a jp nz, UpdateCGBPals ; update gb pals ld a, [$cfc7] ld [rBGP], a ld a, [$cfc8] ld [rOBP0], a ld a, [$cfc9] ld [rOBP1], a and a ret ; 396 VBlank3: ; 396 ; scx, scy ; palettes ; bg map ; tiles ; oam ; sound / lcd stat ; save bank ld a, [hROMBank] ld [$ff8a], a ; scroll x ld a, [hSCX] ld [rSCX], a ; scroll y ld a, [hSCY] ld [rSCY], a ; any pals to update? ld a, [hCGBPalUpdate] and a call nz, ForceUpdateCGBPals jr c, .vblankoccurred ; else call UpdateBGMap call Serve2bppRequest@VBlank ; update oam by dma transfer call hPushOAM ; @PushOAM: ; ld a, Sprites >> 8 ; ld [rDMA], a ; ld a, $28 ; .loop ; dec a ; jr nz, .loop ; ret .vblankoccurred ; tell other fns vblank happened xor a ld [VBlankOccurred], a ; save int flag ld a, [rIF] push af ; reset ints xor a ld [rIF], a ; force lcdstat int during sound update ld a, %10 ; lcd stat ld [rIE], a ld [rIF], a ei ; update sound ld a, BANK(_UpdateSound) rst Bankswitch ; bankswitch call _UpdateSound ; restore bank ld a, [$ff8a] rst Bankswitch di ; request lcdstat ld a, [rIF] ld b, a ; and any other ints pop af or b ld b, a ; reset ints xor a ld [rIF], a ; enable ints besides joypad ld a, %1111 ; serial timer lcdstat vblank ld [rIE], a ; request ints ld a, b ld [rIF], a ret ; 3df VBlank4: ; 3df ; bg map ; tiles ; oam ; joypad ; serial ; sound ; save bank ld a, [hROMBank] ld [$ff8a], a call UpdateBGMap call Serve2bppRequest ; update oam by dma transfer call hPushOAM ; @PushOAM: ; ld a, Sprites >> 8 ; ld [rDMA], a ; ld a, $28 ; .loop ; dec a ; jr nz, .loop ; ret ; update joypad call Joypad ; tell other fns vblank happened xor a ld [VBlankOccurred], a ; handshake call AskSerial ; update sound ld a, BANK(_UpdateSound) rst Bankswitch ; bankswitch call _UpdateSound ; restore bank ld a, [$ff8a] rst Bankswitch ret ; 400 VBlank5: ; 400 ; scx ; palettes ; bg map ; tiles ; joypad ; ; save bank ld a, [hROMBank] ld [$ff8a], a ; scroll x ld a, [hSCX] ld [rSCX], a ; if we can update pals, skip this part call UpdatePalsIfCGB jr c, .vblankoccurred call UpdateBGMap call Serve2bppRequest .vblankoccurred ; tell other fns vblank happened xor a ld [VBlankOccurred], a ; joypad call Joypad ; discard requested ints xor a ld [rIF], a ; enable lcd stat ld a, %10 ; lcd stat ld [rIE], a ; request lcd stat ld [rIF], a ei ; update sound ld a, BANK(_UpdateSound) rst Bankswitch ; bankswitch call _UpdateSound ; restore bank ld a, [$ff8a] rst Bankswitch di ; discard requested ints xor a ld [rIF], a ; enable ints besides joypad ld a, %1111 ; serial timer lcdstat vblank ld [rIE], a ret ; 436 VBlank6: ; 436 ; palettes ; tiles ; dma transfer ; sound ; save bank ld a, [hROMBank] ld [$ff8a], a ; inc frame counter ld hl, $ff9b inc [hl] call UpdateCGBPals jr c, .vblankoccurred call Serve2bppRequest call Serve1bppRequest call DMATransfer .vblankoccurred ; tell other fns vblank happened xor a ld [VBlankOccurred], a ; update sound ld a, BANK(_UpdateSound) rst Bankswitch ; bankswitch call _UpdateSound ; restore bank ld a, [$ff8a] rst Bankswitch ret ; 45a