gameboy/main.asm

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INCLUDE "hardware.inc"
INCLUDE "game/game.asm"
INCLUDE "tools.asm"
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SECTION "InterruptVblank", ROM0[$0040]
reti
SECTION "InterruptLCDC", ROM0[$0048]
reti
SECTION "InterruptTimer_Overflow", ROM0[$0050]
reti
SECTION "InterruptSerial", ROM0[$0058]
reti
SECTION "Interruptp1thru4", ROM0[$0060]
reti
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SECTION "Header", ROM0[$100]
EntryPoint: ;
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ei ; Simple nop ; di ; Disable interrupts for now
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jp Start ; Leave this tiny space
REPT $150 - $104
db 0
ENDR
SECTION "Intro code", ROM0
Start:
; First step is to access the VRAM to insert our graphics data.
; To do so, we must wait until we are in VBLANK period.
; Loop until we find ourselves in VBLANK
; Turn off the LCD
.waitVBlank
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ld a, $01
ld [$FFFF], a ; Force enable VBLANK Interrupt
halt
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xor a ; ld a, 0 ; Reset the accumilator register
; Our target is to set bit 7 reset on the LDC to turn it off
ld [rLCDC], a ; We will have to write to LCDC again later, so it's not a bother, really.
; ----------- Font Begin copying to VRAM -----------
; Start copying our font to vram
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ld de, Page1 ; The start of the font tiles
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ld hl, $9000 ; Set registers hl to $9000 which is the beginning of vram
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ld bc, Page1End - Page1 ; The total length of font tiles
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call Memcpy
; ----------- Start the display -----------
; Init the display register
ld a, %11100100 ; Load the palette of white, light gray, dark gray, black
ld a, %00011011 ; Load the palette of white, light gray, dark gray, black
ld [rBGP], a ; Store the palette to display
xor a ; ld a, 0 ; Reset the accumilator
ld [rSCY], a ; Set our scroll Y position to 0
ld [rSCX], a ; Set our scroll X position to 0
ld [rNR52], a ; Turn off sound
; Turn the screen on, display background
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ld a, LCDCF_ON|LCDCF_BGON
; ld a, %10000001 ; screen on = 8th bit, background display = 1st bit
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ld [rLCDC], a ; Set the screen flags
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ei ; Enable interrupts again?
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jp GameLoop
SECTION "Font", ROM0
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Page1:
INCBIN "assets/page1.chr"
Page1End:
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