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Save 20 bytes in the CGB boot ROM

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This commit is contained in:
Jakub Kądziołka 2019-06-09 15:15:08 +02:00
parent a0c5baecd8
commit 8386aaf12f
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GPG Key ID: E315A75846131564
1 changed files with 31 additions and 42 deletions
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71
BootROMs/cgb_boot.asm
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@ -103,10 +103,11 @@ Start:
; Load Tilemap ; Load Tilemap
ld hl, $98C2 ld hl, $98C2
ld b, 3 ld b, 3
ld a, 8
IF DEF(FAST) IF DEF(FAST)
xor a xor a
ldh [$4F], a ldh [$4F], a
ELSE
ld a, 8
ENDC ENDC
.tilemapLoop .tilemapLoop
@ -120,8 +121,7 @@ IF !DEF(FAST)
; Switch to second VRAM Bank ; Switch to second VRAM Bank
ld a, 1 ld a, 1
ldh [$4F], a ldh [$4F], a
ld a, 8 ld [hl], 8
ld [hl], a
; Switch to back first VRAM Bank ; Switch to back first VRAM Bank
xor a xor a
ldh [$4F], a ldh [$4F], a
@ -628,6 +628,8 @@ ClearMemoryPage:
jr z, ClearMemoryPage jr z, ClearMemoryPage
ret ret
ReadTwoTileLines:
call ReadTileLine
; c = $f0 for even lines, $f for odd lines. ; c = $f0 for even lines, $f for odd lines.
ReadTileLine: ReadTileLine:
ld a, [de] ld a, [de]
@ -647,34 +649,28 @@ ReadTileLine:
.dontSwap .dontSwap
inc hl inc hl
ldi [hl], a ldi [hl], a
swap c
ret ret
ReadCGBLogoHalfTile: ReadCGBLogoHalfTile:
ld c, $f0 call .do_twice
call ReadTileLine .do_twice
ld c, $f call ReadTwoTileLines
call ReadTileLine
inc e
ld c, $f0
call ReadTileLine
ld c, $f
call ReadTileLine
inc e inc e
ld a, e
ret ret
ReadCGBLogoTile: ReadCGBLogoTile:
ld c, $f0
call ReadCGBLogoHalfTile call ReadCGBLogoHalfTile
ld a, e
add a, 22 add a, 22
ld e, a ld e, a
call ReadCGBLogoHalfTile call ReadCGBLogoHalfTile
ld a, e
sub a, 22 sub a, 22
ld e, a ld e, a
ret ret
ReadTrademarkSymbol: ReadTrademarkSymbol:
ld de, TrademarkSymbol ld de, TrademarkSymbol
ld c,$08 ld c,$08
@ -706,19 +702,23 @@ LoadPalettes:
jr nz, .loop jr nz, .loop
ret ret
DoIntroAnimation:
AdvanceIntroAnimation: ; Animate the intro
ld a, 1
ldh [$4F], a
ld d, 26
.animationLoop
ld b, 2
call WaitBFrames
ld hl, $98C0 ld hl, $98C0
ld c, 3 ; Row count ld c, 3 ; Row count
.loop .loop
ld a, [hl] ld a, [hl]
cp $F ; Already blue cp $F ; Already blue
jr z, .nextTile jr z, .nextTile
inc a inc [hl]
ld [hl], a
and $7 and $7
cp $1 ; Changed a white tile, go to next line jr z, .nextLine ; Changed a white tile, go to next line
jr z, .nextLine
.nextTile .nextTile
inc hl inc hl
jr .loop jr .loop
@ -728,18 +728,7 @@ AdvanceIntroAnimation:
ld l, a ld l, a
inc hl inc hl
dec c dec c
ret z jr nz, .loop
jr .loop
DoIntroAnimation:
; Animate the intro
ld a, 1
ldh [$4F], a
ld d, 26
.animationLoop
ld b, 2
call WaitBFrames
call AdvanceIntroAnimation
dec d dec d
jr nz, .animationLoop jr nz, .animationLoop
ret ret
@ -796,7 +785,7 @@ ENDC
.emulateDMGForCGBGame .emulateDMGForCGBGame
call EmulateDMG call EmulateDMG
ldh [$4C], a ldh [$4C], a
ld a, $1; ld a, $1
ret ret
EmulateDMG: EmulateDMG:
@ -833,7 +822,7 @@ GetPaletteIndex:
ld a, [hl] ; Old Licensee ld a, [hl] ; Old Licensee
cp $33 cp $33
jr z, .newLicensee jr z, .newLicensee
cp 1 ; Nintendo dec a ; 1 = Nintendo
jr nz, .notNintendo jr nz, .notNintendo
jr .doChecksum jr .doChecksum
.newLicensee .newLicensee
@ -848,22 +837,22 @@ GetPaletteIndex:
.doChecksum .doChecksum
ld l, $34 ld l, $34
ld c, $10 ld c, $10
ld b, 0 xor a
.checksumLoop .checksumLoop
ld a, [hli] add [hl]
add b inc l
ld b, a
dec c dec c
jr nz, .checksumLoop jr nz, .checksumLoop
ld b, a
; c = 0 ; c = 0
ld hl, TitleChecksums ld hl, TitleChecksums
.searchLoop .searchLoop
ld a, l ld a, l
cp ChecksumsEnd & $FF sub LOW(ChecksumsEnd) ; use sub to zero out a
jr z, .notNintendo ret z
ld a, [hli] ld a, [hli]
cp b cp b
jr nz, .searchLoop jr nz, .searchLoop