ref: 0817dee42ca7482db81a8eb66413e77ad903888f
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 ldh 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 ldh a, [rDIV] ld b, a ldh a, [hRandomAdd] adc b ldh [hRandomAdd], a ldh a, [rDIV] ld b, a ldh a, [hRandomSub] sbc b ldh [hRandomSub], a ldh a, [hROMBank] ldh [hROMBankBackup], a ldh a, [hSCX] ldh [rSCX], a ldh a, [hSCY] ldh [rSCY], a ldh a, [hWY] ldh [rWY], a ldh a, [hWX] ldh [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 ldh 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 UpdateJoypad ld a, BANK(_UpdateSound) rst Bankswitch call _UpdateSound ldh a, [hROMBankBackup] rst Bankswitch ldh a, [hSeconds] ldh [hUnusedBackup], a ret VBlank2:: ; sound only ldh a, [hROMBank] ldh [hROMBankBackup], a ld a, BANK(_UpdateSound) rst Bankswitch call _UpdateSound ldh a, [hROMBankBackup] rst Bankswitch xor a ld [wVBlankOccurred], a ret VBlank1:: ; scx, scy ; palettes ; bg map ; tiles ; oam ; sound / lcd stat ldh a, [hROMBank] ldh [hROMBankBackup], a ldh a, [hSCX] ldh [rSCX], a ldh a, [hSCY] ldh [rSCY], a call UpdatePals jr c, .done call UpdateBGMap call Serve2bppRequest_VBlank call hTransferVirtualOAM .done xor a ld [wVBlankOccurred], a ; get requested ints ldh a, [rIF] ld b, a ; discard requested ints xor a ldh [rIF], a ; enable lcd stat ld a, 1 << LCD_STAT ldh [rIE], a ; rerequest serial int if applicable (still disabled) ; request lcd stat ld a, b and 1 << SERIAL or 1 << LCD_STAT ldh [rIF], a ei ld a, BANK(_UpdateSound) rst Bankswitch call _UpdateSound ldh a, [hROMBankBackup] rst Bankswitch di ; get requested ints ldh a, [rIF] ld b, a ; discard requested ints xor a ldh [rIF], a ; enable ints besides joypad ld a, IE_DEFAULT ldh [rIE], a ; rerequest ints ld a, b ldh [rIF], a ret UpdatePals:: ; update pals for either dmg or cgb ldh a, [hCGB] and a jp nz, UpdateCGBPals ; update gb pals ld a, [wBGP] ldh [rBGP], a ld a, [wOBP0] ldh [rOBP0], a ld a, [wOBP1] ldh [rOBP1], a and a ret VBlank3:: ; scx, scy ; palettes ; bg map ; tiles ; oam ; sound / lcd stat ldh a, [hROMBank] ldh [hROMBankBackup], a ldh a, [hSCX] ldh [rSCX], a ldh a, [hSCY] ldh [rSCY], a ldh a, [hCGBPalUpdate] and a call nz, ForceUpdateCGBPals jr c, .done call UpdateBGMap call Serve2bppRequest_VBlank call hTransferVirtualOAM .done xor a ld [wVBlankOccurred], a ldh a, [rIF] push af xor a ldh [rIF], a ld a, 1 << LCD_STAT ldh [rIE], a ldh [rIF], a ei ld a, BANK(_UpdateSound) rst Bankswitch call _UpdateSound ldh a, [hROMBankBackup] rst Bankswitch di ; request lcdstat ldh a, [rIF] ld b, a ; and any other ints pop af or b ld b, a ; reset ints xor a ldh [rIF], a ; enable ints besides joypad ld a, IE_DEFAULT ldh [rIE], a ; request ints ld a, b ldh [rIF], a ret VBlank4:: ; bg map ; tiles ; oam ; joypad ; serial ; sound ldh a, [hROMBank] ldh [hROMBankBackup], a call UpdateBGMap call Serve2bppRequest call hTransferVirtualOAM call UpdateJoypad xor a ld [wVBlankOccurred], a call AskSerial ld a, BANK(_UpdateSound) rst Bankswitch call _UpdateSound ldh a, [hROMBankBackup] rst Bankswitch ret VBlank5:: ; scx ; palettes ; bg map ; tiles ; joypad ; ldh a, [hROMBank] ldh [hROMBankBackup], a ldh a, [hSCX] ldh [rSCX], a call UpdatePalsIfCGB jr c, .done call UpdateBGMap call Serve2bppRequest .done xor a ld [wVBlankOccurred], a call UpdateJoypad xor a ldh [rIF], a ld a, 1 << LCD_STAT ldh [rIE], a ; request lcd stat ldh [rIF], a ei ld a, BANK(_UpdateSound) rst Bankswitch call _UpdateSound ldh a, [hROMBankBackup] rst Bankswitch di xor a ldh [rIF], a ; enable ints besides joypad ld a, IE_DEFAULT ldh [rIE], a ret VBlank6:: ; palettes ; tiles ; dma transfer ; sound ldh a, [hROMBank] ldh [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 ldh a, [hROMBankBackup] rst Bankswitch ret