76 lines
2.5 KiB
NASM
76 lines
2.5 KiB
NASM
INCLUDE "hardware.inc"
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INCLUDE "game/game.asm"
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INCLUDE "tools.asm"
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SECTION "Header", ROM0[$100]
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EntryPoint: ;
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di ; Disable interrupts. That way we can avoid dealing with them, especially since we didn't talk about them yet
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jp Start ; Leave this tiny space
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REPT $150 - $104
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db 0
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ENDR
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SECTION "Intro code", ROM0
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Start:
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; First step is to access the VRAM to insert our graphics data.
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; To do so, we must wait until we are in VBLANK period.
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; Loop until we find ourselves in VBLANK
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; Turn off the LCD
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.waitVBlank
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ld a, [rLY] ; Load the current vertical line being rendered
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cp 144 ; Check if we're past VBlank (1 to 144 = carry bit set)
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jr c, .waitVBlank ; Jump back to waitVBlank if rLY is less than 144
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xor a ; ld a, 0 ; Reset the accumilator register
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; Our target is to set bit 7 reset on the LDC to turn it off
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ld [rLCDC], a ; We will have to write to LCDC again later, so it's not a bother, really.
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; ----------- Font Begin copying to VRAM -----------
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; Start copying our font to vram
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ld de, FontTiles ; 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, FontTilesEnd - FontTiles ; The total length of font tiles
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call Memcpy
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; ----------- Begin copying string to palette -----------
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ld hl, $9800 ; This will print the string at the top-left corner of screen
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ld de, HelloWorldStr
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.copyString
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ld a, [de] ; Read the first byte in the string to accumilator
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ld [hli], a ; Write the byte from the accumilator to the destination while incrementing destination address
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inc de ; Move to next byte in string
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and a ; AND a with A, Checking if we copied a zero (end of string)
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jr nz, .copyString ; Continue copying while not zero
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; ----------- Start the display -----------
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; Init the display register
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ld a, %11100100 ; Load the palette of white, light gray, dark gray, black
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ld a, %00011011 ; Load the palette of white, light gray, dark gray, black
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ld [rBGP], a ; Store the palette to display
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xor a ; ld a, 0 ; Reset the accumilator
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ld [rSCY], a ; Set our scroll Y position to 0
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ld [rSCX], a ; Set our scroll X position to 0
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ld [rNR52], a ; Turn off sound
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; Turn the screen on, display background
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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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jp GameLoop
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SECTION "Font", ROM0
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FontTiles:
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INCBIN "font.chr"
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FontTilesEnd:
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Section "Hello wrold string", ROM0
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HelloWorldStr:
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db "Hello World!", 0
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