main.asm

;****************************************************************************************************************************************************
;*  Includes
;****************************************************************************************************************************************************

    INCLUDE "tileData/alice.inc"

;****************************************************************************************************************************************************
;*  user data [constants]
;****************************************************************************************************************************************************


;****************************************************************************************************************************************************
;*  equates
;****************************************************************************************************************************************************

;****************************************************************************************************************************************************
;*  macros
;****************************************************************************************************************************************************

;****************************************************************************************************************************************************
;*  cartridge header
;****************************************************************************************************************************************************

    SECTION "Org $00",ROM0[$00]
RST_00:
    jp  $100

    SECTION "Org $08",ROM0[$08]
RST_08:
    jp  $100

    SECTION "Org $10",ROM0[$10]
RST_10:
    jp  $100

    SECTION "Org $18",ROM0[$18]
RST_18:
    jp  $100

    SECTION "Org $20",ROM0[$20]
RST_20:
    jp  $100

    SECTION "Org $28",ROM0[$28]
RST_28:
    jp  $100

    SECTION "Org $30",ROM0[$30]
RST_30:
    jp  $100

    SECTION "Org $38",ROM0[$38]
RST_38:
    jp  $100

    SECTION "V-Blank IRQ Vector",ROM0[$40]
VBL_VECT:
    jp VBlank

    SECTION "LCD IRQ Vector",ROM0[$48]
LCD_VECT:
    reti

    SECTION "Timer IRQ Vector",ROM0[$50]
TIMER_VECT:
    reti

    SECTION "Serial IRQ Vector",ROM0[$58]
SERIAL_VECT:
    reti

    SECTION "Joypad IRQ Vector",ROM0[$60]
JOYPAD_VECT:
    reti

    SECTION "Start",ROM0[$100]
    nop
    jp  Start

    ; $0104-$0133 [Nintendo logo - do _not_ modify the logo data here or the GB will not run the program]
    DB  $CE,$ED,$66,$66,$CC,$0D,$00,$0B,$03,$73,$00,$83,$00,$0C,$00,$0D
    DB  $00,$08,$11,$1F,$88,$89,$00,$0E,$DC,$CC,$6E,$E6,$DD,$DD,$D9,$99
    DB  $BB,$BB,$67,$63,$6E,$0E,$EC,$CC,$DD,$DC,$99,$9F,$BB,$B9,$33,$3E

    ; $0134-$013E [Game title - up to 11 upper case ASCII characters, pad with $00]
    DB  "ALICE IMAGE"
        ;0123456789A

    ; $013F-$0142 [Product code - 4 ASCII characters, assigned by Nintendo, just leave blank]
    DB  "    "
        ;0123

    ; $0143 [Color GameBoy compatibility code]
    DB  $00 ; $00 - DMG
            ; $80 - DMG/GBC
            ; $C0 - GBC Only cartridge

    ; $0144 [High-nibble of license code - normally $00 if $014B != $33]
    DB  $00

    ; $0145 [Low-nibble of license code - normally $00 if $014B != $33]
    DB  $00

    ; $0146 [GameBoy/Super GameBoy indicator]
    DB  $00 ; $00 - GameBoy

    ; $0147 [Cartridge type - all Color GameBoy cartridges are at least $19]
    DB  $00 ; $00 - ROM Only

    ; $0148 [ROM size]
    DB  $00 ; $00 - 256Kbit = 32Kbyte = 2 banks

    ; $0149 [RAM size]
    DB  $00 ; $00 - None

    ; $014A [Destination code]
    DB  $01 ; $01 - All others
            ; $00 - Japan

    ; $014B [Licensee code - this _must_ be $33]
    DB  $33 ; $33 - Check $0144/$0145 for Licensee code.

    ; $014C [Mask ROM version - handled by RGBFIX]
    DB  $00

    ; $014D [Complement check - handled by RGBFIX]
    DB  $00

    ; $014E-$014F [Cartridge checksum - handled by RGBFIX]
    DW  $00


;****************************************************************************************************************************************************
;*  Program Start
;****************************************************************************************************************************************************

    SECTION "Program Start",ROM0[$0150]
Start:
    ld  sp,$FFFE            ;set the stack pointer to $FFFE

    call clearWRAM          ;Clear the Work RAM

    ei
    ld a, $01
    ld [$FFFF], a

Loop:

.waitVBlankDone:
    ld a, [$C002]
    cp a, $01
    jr nz, .waitVBlankDone
    ld a, $00
    ld [$C002], a

    jp Loop

;***************************************************************
;* Subroutines
;***************************************************************

    SECTION "Support Routines",ROM0

clearWRAM:
    ld hl, $C000
    ld bc, $1FFF
.clearWRAMLoop:
    ld a, $00
    ld [hl], a
    inc hl
    dec bc
    ld a, b
    or c
    jr nz, .clearWRAMLoop
    ret

clearOAM:
    ld hl, $FE00
    ld bc, 40*4
.clearOAMLoop:
    ld a, $00
    ld [hl], a
    inc hl
    dec bc
    ld a, b
    or c
    jr nz, .clearOAMLoop
    ret

clearMap:
    ld hl, $9800
    ld de, $9C00
    ld bc, 32*32
.clearMapLoop:
    ld a, $00
    ld [hl], a
    ld [de], a
    inc hl
    inc de
    dec bc
    ld a, b
    or c
    jr nz, .clearMapLoop
    ret

loadTiles:
.loadTilesLoop:
    ld a, [hl]
    ld [de], a
    inc hl
    inc de
    dec bc
    ld a, b
    or c
    jr nz, .loadTilesLoop
    ret

placeImage:
    ld a, $00
    ld [$9800], a
    ld a, $01
    ld [$9801], a
    ld a, $02
    ld [$9802], a
    ld a, $03
    ld [$9803], a
    ret

VBlank:
    ld a, [$C001]
    cp a, $01
    jr z, .skipInit

.waitRealVBlank:
    ld  a,[$FF44]           ;get current scanline
    cp  $91                 ;Are we in v-blank yet?
    jr  nz, .waitRealVBlank ;if A != 0x91 then loop

    ld  a, $00              ;Load 0x00 to A
    ld  [$FF40],a           ;turn off LCD

    call clearOAM           ;Clear OAM
    call clearMap           ;Clear BG

    ld hl, alice3_tile_data     ;Load a pointer to the tiles into HL
    ld de, $8000                ;Load the destination in VRAM to DE
    ld bc, alice3_tile_data_size;Load the number of bytes to load into BC
    call loadTiles              ;Load the tiles

    call placeImage

    ld a, %11100100         ;Load 0xE4 to A
    ld [$FF47], a           ;Load A into 0xFF47 (DMG BG Shades)
    ld [$FF48], a           ;Load A into 0xFF48 (DMG Sprite Shades)

    ld  a, $D2
    ld  [$FF40],a           ;Turn on the LCD, BG, etc

    ld a, $01
    ld [$C001], a

.skipInit:

    ld a, $01
    ld [$C002], a
    reti