mirror of https://github.com/pret/pokecrystal.git
487 lines
5.7 KiB
NASM
487 lines
5.7 KiB
NASM
; Functions dealing with VRAM.
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DMATransfer:: ; 15d8
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; Return carry if the transfer is completed.
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ld a, [hDMATransfer]
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and a
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ret z
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; Start transfer
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ld [rHDMA5], a
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; Execution is halted until the transfer is complete.
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xor a
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ld [hDMATransfer], a
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scf
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ret
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; 15e3
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UpdateBGMapBuffer:: ; 15e3
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; Copy [hFFDC] 16x8 tiles from BGMapBuffer
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; to bg map addresses in BGMapBufferPtrs.
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; [hFFDC] must be even since this is done in pairs.
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; Return carry on success.
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ld a, [hBGMapUpdate]
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and a
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ret z
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ld a, [rVBK]
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push af
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ld [hSPBuffer], sp
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ld hl, BGMapBufferPtrs
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ld sp, hl
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; We can now pop the addresses of affected spots on the BG Map
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ld hl, BGMapPalBuffer
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ld de, BGMapBuffer
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.next
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; Copy a pair of 16x8 blocks (one 16x16 block)
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rept 2
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; Get our BG Map address
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pop bc
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; Palettes
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ld a, 1
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ld [rVBK], a
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ld a, [hli]
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ld [bc], a
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inc c
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ld a, [hli]
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ld [bc], a
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dec c
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; Tiles
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ld a, 0
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ld [rVBK], a
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ld a, [de]
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inc de
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ld [bc], a
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inc c
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ld a, [de]
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inc de
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ld [bc], a
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endr
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; We've done 2 16x8 blocks
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ld a, [hFFDC]
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dec a
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dec a
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ld [hFFDC], a
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jr nz, .next
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ld a, [hSPBuffer]
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ld l, a
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ld a, [hSPBuffer + 1]
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ld h, a
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ld sp, hl
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pop af
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ld [rVBK], a
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xor a
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ld [hBGMapUpdate], a
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scf
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ret
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; 163a
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WaitTop:: ; 163a
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; Wait until the top third of the BG Map is being updated.
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ld a, [hBGMapMode]
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and a
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ret z
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ld a, [hBGMapThird]
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and a
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jr z, .done
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call DelayFrame
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jr WaitTop
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.done
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xor a
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ld [hBGMapMode], a
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ret
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; 164c
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UpdateBGMap:: ; 164c
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; Update the BG Map, in thirds, from TileMap and AttrMap.
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ld a, [hBGMapMode]
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and a
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ret z
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; BG Map 0
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dec a ; 1
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jr z, .Tiles
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dec a ; 2
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jr z, .Attr
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; BG Map 1
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dec a
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ld a, [hBGMapAddress]
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ld l, a
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ld a, [hBGMapAddress + 1]
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ld h, a
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push hl
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xor a ; LOW(vBGMap1)
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ld [hBGMapAddress], a
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ld a, HIGH(vBGMap1)
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ld [hBGMapAddress + 1], a
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ld a, [hBGMapMode]
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push af
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cp 3
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call z, .Tiles
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pop af
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cp 4
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call z, .Attr
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pop hl
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ld a, l
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ld [hBGMapAddress], a
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ld a, h
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ld [hBGMapAddress + 1], a
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ret
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.Attr:
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ld a, 1
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ld [rVBK], a
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hlcoord 0, 0, AttrMap
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call .update
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ld a, 0
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ld [rVBK], a
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ret
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.Tiles:
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hlcoord 0, 0
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.update
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ld [hSPBuffer], sp
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; Which third?
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ld a, [hBGMapThird]
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and a ; 0
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jr z, .top
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dec a ; 1
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jr z, .middle
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; 2
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THIRD_HEIGHT EQU SCREEN_HEIGHT / 3
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.bottom
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ld de, 2 * THIRD_HEIGHT * SCREEN_WIDTH
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add hl, de
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ld sp, hl
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ld a, [hBGMapAddress + 1]
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ld h, a
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ld a, [hBGMapAddress]
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ld l, a
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ld de, 2 * THIRD_HEIGHT * BG_MAP_WIDTH
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add hl, de
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; Next time: top third
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xor a
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jr .start
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.middle
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ld de, THIRD_HEIGHT * SCREEN_WIDTH
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add hl, de
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ld sp, hl
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ld a, [hBGMapAddress + 1]
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ld h, a
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ld a, [hBGMapAddress]
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ld l, a
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ld de, THIRD_HEIGHT * BG_MAP_WIDTH
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add hl, de
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; Next time: bottom third
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ld a, 2
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jr .start
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.top
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ld sp, hl
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ld a, [hBGMapAddress + 1]
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ld h, a
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ld a, [hBGMapAddress]
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ld l, a
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; Next time: middle third
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ld a, 1
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.start
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; Which third to update next time
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ld [hBGMapThird], a
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; Rows of tiles in a third
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ld a, SCREEN_HEIGHT / 3
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; Discrepancy between TileMap and BGMap
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ld bc, BG_MAP_WIDTH - (SCREEN_WIDTH - 1)
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.row
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; Copy a row of 20 tiles
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rept SCREEN_WIDTH / 2 - 1
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pop de
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ld [hl], e
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inc l
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ld [hl], d
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inc l
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endr
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pop de
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ld [hl], e
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inc l
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ld [hl], d
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add hl, bc
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dec a
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jr nz, .row
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ld a, [hSPBuffer]
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ld l, a
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ld a, [hSPBuffer + 1]
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ld h, a
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ld sp, hl
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ret
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; 170a
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Serve1bppRequest:: ; 170a
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; Only call during the first fifth of VBlank
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ld a, [Requested1bpp]
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and a
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ret z
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; Back out if we're too far into VBlank
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ld a, [rLY]
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cp LY_VBLANK
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ret c
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cp LY_VBLANK + 2
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ret nc
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; Copy [Requested1bpp] 1bpp tiles from [Requested1bppSource] to [Requested1bppDest]
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ld [hSPBuffer], sp
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; Source
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ld hl, Requested1bppSource
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ld a, [hli]
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ld h, [hl]
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ld l, a
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ld sp, hl
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; Destination
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ld hl, Requested1bppDest
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ld a, [hli]
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ld h, [hl]
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ld l, a
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; # tiles to copy
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ld a, [Requested1bpp]
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ld b, a
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xor a
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ld [Requested1bpp], a
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.next
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rept 3
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pop de
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ld [hl], e
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inc l
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ld [hl], e
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inc l
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ld [hl], d
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inc l
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ld [hl], d
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inc l
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endr
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pop de
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ld [hl], e
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inc l
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ld [hl], e
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inc l
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ld [hl], d
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inc l
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ld [hl], d
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inc hl
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dec b
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jr nz, .next
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ld a, l
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ld [Requested1bppDest], a
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ld a, h
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ld [Requested1bppDest + 1], a
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ld [Requested1bppSource], sp
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ld a, [hSPBuffer]
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ld l, a
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ld a, [hSPBuffer + 1]
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ld h, a
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ld sp, hl
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ret
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; 1769
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Serve2bppRequest:: ; 1769
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; Only call during the first fifth of VBlank
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ld a, [Requested2bpp]
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and a
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ret z
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; Back out if we're too far into VBlank
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ld a, [rLY]
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cp LY_VBLANK
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ret c
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cp LY_VBLANK + 2
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ret nc
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jr _Serve2bppRequest
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Serve2bppRequest@VBlank:: ; 1778
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ld a, [Requested2bpp]
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and a
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ret z
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_Serve2bppRequest:: ; 177d
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; Copy [Requested2bpp] 2bpp tiles from [Requested2bppSource] to [Requested2bppDest]
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ld [hSPBuffer], sp
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; Source
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ld hl, Requested2bppSource
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ld a, [hli]
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ld h, [hl]
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ld l, a
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ld sp, hl
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; Destination
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ld hl, Requested2bppDest
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ld a, [hli]
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ld h, [hl]
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ld l, a
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; # tiles to copy
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ld a, [Requested2bpp]
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ld b, a
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xor a
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ld [Requested2bpp], a
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.next
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rept 7
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pop de
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ld [hl], e
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inc l
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ld [hl], d
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inc l
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endr
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pop de
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ld [hl], e
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inc l
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ld [hl], d
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inc hl
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dec b
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jr nz, .next
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ld a, l
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ld [Requested2bppDest], a
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ld a, h
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ld [Requested2bppDest + 1], a
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ld [Requested2bppSource], sp
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ld a, [hSPBuffer]
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ld l, a
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ld a, [hSPBuffer + 1]
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ld h, a
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ld sp, hl
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ret
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; 17d3
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AnimateTileset:: ; 17d3
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; Only call during the first fifth of VBlank
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ld a, [hMapAnims]
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and a
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ret z
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; Back out if we're too far into VBlank
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ld a, [rLY]
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cp LY_VBLANK
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ret c
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cp LY_VBLANK + 7
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ret nc
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ld a, [hROMBank]
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push af
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ld a, BANK(_AnimateTileset)
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rst Bankswitch
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ld a, [rSVBK]
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push af
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ld a, BANK(TilesetAnim)
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ld [rSVBK], a
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ld a, [rVBK]
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push af
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ld a, 0
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ld [rVBK], a
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call _AnimateTileset
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pop af
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ld [rVBK], a
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pop af
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ld [rSVBK], a
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pop af
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rst Bankswitch
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ret
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; 17ff
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