diff options
| -rwxr-xr-x | main.asm | 111 |
1 files changed, 60 insertions, 51 deletions
@@ -24,58 +24,58 @@ Start: ; 0x150 di xor a ld [$ff0f], a - ld a, [$ff40] - bit 7, a - jr nz, .asm_163 + ld a, [$ff40] ; LCD Control + bit 7, a ; Check if LCD Display is enabled + jr nz, .LCDDisplayEnabled set 7, a ld [$ff40], a -.asm_163 +.LCDDisplayEnabled ld bc, $0002 call Func_948 -.asm_169 - ld a, [$ff44] - cp $91 - jr c, .asm_169 +.waitForVBlank + ld a, [$ff44] ; LY register (LCDC Y-Coordinate) + cp 145 ; > 144 means V-Blank + jr c, .waitForVBlank ld a, $81 - ld [$ff40], a + ld [$ff40], a ; Enable LCD Display xor a - ld [$ff47], a + ld [$ff47], a ; Clear Palette Data ld [$ff48], a ld [$ff49], a ld bc, $0002 call Func_948 -.asm_180 - ld a, [$ff44] - cp $91 - jr c, .asm_180 +.waitForVBlank2 + ld a, [$ff44] ; LY register (LCDC Y-Coordinate) + cp 145 ; > 144 means V-Blank + jr c, .waitForVBlank2 xor a - ld [$ff40], a + ld [$ff40], a ; Disable LCD Display ld hl, wc000 ld bc, $2000 - call Func_654 + call ClearData ; Clear WRAM Bank 0 ld hl, $8000 ld bc, $1000 - call Func_654 + call ClearData ; Clear First half of VRAM ld a, $a - ld [$0000], a + ld [$0000], a ; Enable RAM ld a, $1 - ld [$2000], a + ld [$2000], a ; Load ROM Bank $1 ld a, $0 - ld [$6000], a + ld [$6000], a ; Enable ROM Banking Mode ld a, $0 - ld [$4000], a + ld [$4000], a ; Set bits 5 and 6 of ROM Bank Number ld a, $1 ld [$fff8], a ld a, $1 - ld [$6000], a + ld [$6000], a ; Enable RAM Banking Mode ld a, $0 - ld [$4000], a - ld sp, $dfff + ld [$4000], a ; Load RAM Bank $0 + ld sp, $dfff ; Initialize stack pointer to the end of WRAM Bank $1 ld hl, $ff80 ld bc, $007e - call Func_654 - call Func_5f7 - call Func_916 + call ClearData ; Clear High RAM (HRAM) + call InitializeHRAM + call ClearOAMBuffer xor a ld [$d7fb], a ld [$d7fc], a @@ -120,16 +120,16 @@ Start: ; 0x150 ld [$d917], a .asm_222 ld a, $1 - ld [$ffff], a + ld [$ffff], a ; Only enable LCD Status interrupt ei ld a, $ff ld [$d810], a call Func_97a xor a ld [$daa3], a - ld a, $0 - ld hl, $1ffc - call Func_549 + ld a, Bank(Func_1ffc) + ld hl, Func_1ffc + call SwitchBank Func_23b: ; 0x23b ld a, [$fffe] cp $11 @@ -185,14 +185,15 @@ Func_532: ; 0x532 ld l, e jp Func_54f -Func_549: ; 0x549 +SwitchBank: ; 0x549 +; Switches to Bank in register a and jumps to hl. ld [$fff8], a - ld [$2000], a + ld [$2000], a ; Load Bank jp [hl] Func_54f: ; 0x54f ld e, a - ld a, [$fff8] + ld a, [$fff8] ; currently-loaded Bank cp e jr z, .asm_570 push af @@ -283,28 +284,35 @@ Func_5c2: ; 0x5c2 INCBIN "baserom.gbc",$5e1,$5f7 - $5e1 -Func_5f7: ; 0x5f7 +InitializeHRAM: ; 0x5f7 +; Initializes registers $ff80 - $ff8a ld c, $80 - ld b, $a - ld hl, $0605 ; todo -.asm_5fe + ld b, $a ; number of bytes to load + ld hl, InitialHRAM +.loop ld a, [hli] - ld [$ff00+c], a + ld [$ff00+c], a ; add register c to $ff00, and store register a into the resulting address inc c dec b - jr nz, .asm_5fe + jr nz, .loop ret -INCBIN "baserom.gbc",$605,$654 - $605 +InitialHRAM: +; These $a bytes are initially load into $ff80 - $ff8a by InitializeHRAM. + db $3e, $d0, $e0, $46, $3e, $28, $3d, $20, $fd, $c9 + +INCBIN "baserom.gbc",$60f,$654 - $60f -Func_654: ; 0x654 +ClearData: ; 0x654 +; Clears bc bytes starting at hl. +; bc can be a maximum of $7fff, since it checks bit 7 of b when looping. xor a dec bc -.asm_656 +.clearLoop ld [hli], a dec bc bit 7, b - jr z, .asm_656 + jr z, .clearLoop ret Func_65d: ; 0x65d @@ -427,14 +435,15 @@ Func_724: ; 0x724 INCBIN "baserom.gbc",$735,$916 - $735 -Func_916: ; 0x916 - ld hl, wOAMBuffer - ld b, $a0 - ld a, $f0 -.asm_91d +ClearOAMBuffer: ; 0x916 +; Clears the OAM buffer by loading $f0 into all of the entries. + ld hl, wOAMBuffer ; 0xd000 + ld b, 4 * 40 ; wOAMBuffer is 4 * 40 bytes long (40 OAM entries, 4 bytes each) + ld a, $f0 ; byte to write +.loop ld [hli], a dec b - jr nz, .asm_91d + jr nz, .loop xor a ld [$d802], a ret @@ -1284,7 +1293,7 @@ Func_821e: ; 0x821e ld a, [$fffe] ld hl, .data_825e call Func_6a4 - call Func_916 + call ClearOAMBuffer call Func_b66 call Func_588 call Func_14a4 |