ref: 9dec80b07e3638c722b9768a1ca0184edea20392
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:: push af push bc push de push hl ld a, [hVBlank] and 7 ld e, a ld d, 0 ld hl, .VBlanks add hl, de add hl, de ld a, [hli] ld h, [hl] ld l, a call _hl_ call GameTimer pop hl pop de pop bc pop af reti .VBlanks: dw VBlank0 dw VBlank1 dw VBlank2 dw VBlank3 dw VBlank4 dw VBlank5 dw VBlank6 dw VBlank0 ; just in case VBlank0:: ; normal operation ; rng ; scx, scy, wy, wx ; bg map buffer ; palettes ; dma transfer ; bg map ; tiles ; oam ; joypad ; sound ; inc frame counter ld hl, hVBlankCounter inc [hl] ; advance random variables 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 ld a, [hROMBank] ld [hROMBankBackup], a ld a, [hSCX] ld [rSCX], a ld a, [hSCY] ld [rSCY], a ld a, [hWY] ld [rWY], a ld a, [hWX] ld [rWX], a ; There's only time to call one of these in one vblank. ; Calls are in order of priority. call UpdateBGMapBuffer jr c, .done call UpdatePalsIfCGB jr c, .done call DMATransfer jr c, .done call UpdateBGMap ; These have their own timing checks. call Serve2bppRequest call Serve1bppRequest call AnimateTileset .done ld a, [hOAMUpdate] and a jr nz, .done_oam call hTransferVirtualOAM .done_oam ; vblank-sensitive operations are done xor a ld [wVBlankOccurred], a ld a, [wOverworldDelay] and a jr z, .ok dec a ld [wOverworldDelay], a .ok ld a, [wTextDelayFrames] and a jr z, .ok2 dec a ld [wTextDelayFrames], a .ok2 call Joypad ld a, BANK(_UpdateSound) rst Bankswitch call _UpdateSound ld a, [hROMBankBackup] rst Bankswitch ld a, [hSeconds] ld [hSecondsBackup], a ret VBlank2:: ; sound only ld a, [hROMBank] ld [hROMBankBackup], a ld a, BANK(_UpdateSound) rst Bankswitch call _UpdateSound ld a, [hROMBankBackup] rst Bankswitch xor a ld [wVBlankOccurred], a ret VBlank1:: ; scx, scy ; palettes ; bg map ; tiles ; oam ; sound / lcd stat ld a, [hROMBank] ld [hROMBankBackup], a ld a, [hSCX] ld [rSCX], a ld a, [hSCY] ld [rSCY], a call UpdatePals jr c, .done call UpdateBGMap call Serve2bppRequest_VBlank call hTransferVirtualOAM .done xor a ld [wVBlankOccurred], 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 ld a, BANK(_UpdateSound) rst Bankswitch call _UpdateSound ld a, [hROMBankBackup] 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 UpdatePals:: ; update pals for either dmg or cgb ld a, [hCGB] and a jp nz, UpdateCGBPals ; update gb pals ld a, [wBGP] ld [rBGP], a ld a, [wOBP0] ld [rOBP0], a ld a, [wOBP1] ld [rOBP1], a and a ret VBlank3:: ; scx, scy ; palettes ; bg map ; tiles ; oam ; sound / lcd stat ld a, [hROMBank] ld [hROMBankBackup], a ld a, [hSCX] ld [rSCX], a ld a, [hSCY] ld [rSCY], a ld a, [hCGBPalUpdate] and a call nz, ForceUpdateCGBPals jr c, .done call UpdateBGMap call Serve2bppRequest_VBlank call hTransferVirtualOAM .done xor a ld [wVBlankOccurred], a ld a, [rIF] push af xor a ld [rIF], a ld a, %10 ; lcd stat ld [rIE], a ld [rIF], a ei ld a, BANK(_UpdateSound) rst Bankswitch call _UpdateSound ld a, [hROMBankBackup] 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 VBlank4:: ; bg map ; tiles ; oam ; joypad ; serial ; sound ld a, [hROMBank] ld [hROMBankBackup], a call UpdateBGMap call Serve2bppRequest call hTransferVirtualOAM call Joypad xor a ld [wVBlankOccurred], a call AskSerial ld a, BANK(_UpdateSound) rst Bankswitch call _UpdateSound ld a, [hROMBankBackup] rst Bankswitch ret VBlank5:: ; scx ; palettes ; bg map ; tiles ; joypad ; ld a, [hROMBank] ld [hROMBankBackup], a ld a, [hSCX] ld [rSCX], a call UpdatePalsIfCGB jr c, .done call UpdateBGMap call Serve2bppRequest .done xor a ld [wVBlankOccurred], a call Joypad xor a ld [rIF], a ld a, %10 ; lcd stat ld [rIE], a ; request lcd stat ld [rIF], a ei ld a, BANK(_UpdateSound) rst Bankswitch call _UpdateSound ld a, [hROMBankBackup] rst Bankswitch di xor a ld [rIF], a ; enable ints besides joypad ld a, %1111 ; serial timer lcdstat vblank ld [rIE], a ret VBlank6:: ; palettes ; tiles ; dma transfer ; sound ld a, [hROMBank] ld [hROMBankBackup], a ; inc frame counter ld hl, hVBlankCounter inc [hl] call UpdateCGBPals jr c, .done call Serve2bppRequest call Serve1bppRequest call DMATransfer .done xor a ld [wVBlankOccurred], a ld a, BANK(_UpdateSound) rst Bankswitch call _UpdateSound ld a, [hROMBankBackup] rst Bankswitch ret