1 files changed, 442 insertions, 0 deletions
diff --git a/home/vblank.asm b/home/vblank.asm
new file mode 100644
index 00000000..1c0824c5
--- /dev/null
+++ b/home/vblank.asm
@@ -0,0 +1,442 @@
+; 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
+
+	ld a, [hVBlank]
+	and 7
+
+	ld e, a
+	ld d, 0
+	ld hl, .VBlanks
+rept 2
+	add hl, de
+endr
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+
+	call _hl_
+
+	call GameTimer
+
+	pop hl
+	pop de
+	pop bc
+	pop af
+	reti
+; 2a1
+
+.VBlanks ; 2a1
+	dw VBlank0
+	dw VBlank1
+	dw VBlank2
+	dw VBlank3
+	dw VBlank4
+	dw VBlank5
+	dw VBlank6
+	dw VBlank0 ; just in case
+; 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, 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 hPushOAM
+.done_oam
+
+
+	; vblank-sensitive operations are done
+
+	xor a
+	ld [VBlankOccurred], a
+
+	ld a, [OverworldDelay]
+	and a
+	jr z, .ok
+	dec a
+	ld [OverworldDelay], a
+.ok
+
+	ld a, [TextDelayFrames]
+	and a
+	jr z, .ok2
+	dec a
+	ld [TextDelayFrames], a
+.ok2
+
+	call Joypad
+
+	ld a, BANK(_UpdateSound)
+	rst Bankswitch
+	call _UpdateSound
+	ld a, [hROMBankBackup]
+	rst Bankswitch
+
+	ld a, [hSeconds]
+	ld [hSecondsBackup], a
+
+	ret
+; 325
+
+
+VBlank2:: ; 325
+; sound only
+
+	ld a, [hROMBank]
+	ld [hROMBankBackup], a
+
+	ld a, BANK(_UpdateSound)
+	rst Bankswitch
+	call _UpdateSound
+
+	ld a, [hROMBankBackup]
+	rst Bankswitch
+
+	xor a
+	ld [VBlankOccurred], a
+	ret
+; 337
+
+
+VBlank1:: ; 337
+; 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 hPushOAM
+.done
+
+	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
+	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
+; 37f
+
+
+UpdatePals:: ; 37f
+; 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
+; 396
+
+
+VBlank3:: ; 396
+; 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 hPushOAM
+.done
+
+	xor a
+	ld [VBlankOccurred], 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
+; 3df
+
+
+VBlank4:: ; 3df
+; bg map
+; tiles
+; oam
+; joypad
+; serial
+; sound
+
+	ld a, [hROMBank]
+	ld [hROMBankBackup], a
+
+	call UpdateBGMap
+	call Serve2bppRequest
+
+	call hPushOAM
+
+	call Joypad
+
+	xor a
+	ld [VBlankOccurred], a
+
+	call AskSerial
+
+	ld a, BANK(_UpdateSound)
+	rst Bankswitch
+	call _UpdateSound
+
+	ld a, [hROMBankBackup]
+	rst Bankswitch
+	ret
+; 400
+
+
+VBlank5:: ; 400
+; 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 [VBlankOccurred], 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
+; 436
+
+
+VBlank6:: ; 436
+; 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 [VBlankOccurred], a
+
+	ld a, BANK(_UpdateSound)
+	rst Bankswitch
+	call _UpdateSound
+
+	ld a, [hROMBankBackup]
+	rst Bankswitch
+	ret
+; 45a