pokecrystal/home/vblank.asm

422 lines
5.4 KiB
NASM

; 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 [hSecondsBackup], 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