mirror of https://github.com/bsnes-emu/bsnes.git
More accurate CGB initial register values. Closes #80
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@ -10,6 +10,8 @@ Start:
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xor a
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; Clear chosen input palette
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ldh [InputPalette], a
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; Clear title checksum
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ldh [TitleChecksum], a
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; Clear memory VRAM
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ld hl, $8000
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call ClearMemoryPage
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@ -723,39 +725,38 @@ Preboot:
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cpl
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ldh [$00], a
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call ClearVRAMViaHDMA
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; Final values for CGB mode
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ld de, $ff56
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ld l, $0d
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ld a, [$143]
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bit 7, a
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jr nz, .cgbGame
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call EmulateDMG
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.cgbGame
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call z, EmulateDMG
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ldh a, [TitleChecksum]
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ld b, a
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ldh [$4C], a ; One day, I will know what this switch does and how it differs from FF6C
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ldh a, [InputPalette]
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and a
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jr nz, .emulateDMGForCGBGame
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IF DEF(AGB)
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; Set registers to match the original AGB-CGB boot
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ld bc, $1100
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push bc
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pop af
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; AF = $1100, C = 0
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xor a
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ld c, a
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add a, $11
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ld h, c
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ld b, 1
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ld c, c
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ld e, $08
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ld l, $7c
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ELSE
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; Set registers to match the original CGB boot
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ld bc, $1180
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push bc
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pop af
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ld c, 0
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; AF = $1180, C = 0
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xor a
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ld c, a
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ld a, $11
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ld h, c
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ld b, c
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ld c, c
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ld e, $08
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ld l, $7c
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; B is set to the title checksum
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ENDC
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ret
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@ -788,25 +789,31 @@ EmulateDMG:
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call WaitFrame
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call LoadPalettesFromIndex
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ld a, 4
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; Set the final values for DMG mode
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ld d, 0
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ld e, $8
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ld l, $7c
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ret
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GetPaletteIndex:
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ld a, [$14B] ; Old Licensee
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ld hl, $14B
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ld a, [hl] ; Old Licensee
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cp $33
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jr z, .newLicensee
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cp 1 ; Nintendo
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jr nz, .notNintendo
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jr .doChecksum
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.newLicensee
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ld a, [$144]
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ld l, $44
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ld a, [hli]
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cp "0"
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jr nz, .notNintendo
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ld a, [$145]
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ld a, [hl]
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cp "1"
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jr nz, .notNintendo
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.doChecksum
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ld hl, $134
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ld l, $34
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ld c, $10
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ld b, 0
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@ -848,6 +855,8 @@ GetPaletteIndex:
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ld a, l
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add PalettePerChecksum - TitleChecksums - 1; -1 since hl was incremented
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ld l, a
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ld a, b
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ldh [TitleChecksum], a
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ld a, [hl]
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ret
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@ -1140,6 +1149,8 @@ SECTION "ROMMax", ROM0[$900]
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ds 1
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SECTION "HRAM", HRAM[$FF80]
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TitleChecksum:
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ds 1
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BgPalettes:
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ds 8 * 4 * 2
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InputPalette:
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