Something went wrong. Try again.
Monorepo for Aesthetic.Computer aesthetic.computer
Something went wrong. Try again.
4.4 kB · 86 lines
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687; Background Tile Example for the Nintendo Game Boy; by Dave VanEe 2022; Tested with RGBDS 1.0.0; License: CC0 (https://creativecommons.org/publicdomain/zero/1.0/)
include "hardware.inc" ; Include hardware definitions so we can use nice names for things
; Define a section that starts at the point the bootrom execution endsSECTION "Start", ROM0[$0100] jp EntryPoint ; Jump past the header space to our actual code
ds $150-@, 0 ; Allocate space for RGBFIX to insert our ROM header by allocating ; the number of bytes from our current location (@) to the end of the ; header ($150)
EntryPoint: di ; Disable interrupts as we won't be using them ld sp, $e000 ; Set the stack pointer to the end of WRAM
; Turn off the LCD when it's safe to do so (during VBlank).waitVBlank ldh a, [rLY] ; Read the LY register to check the current scanline cp SCREEN_HEIGHT_PX ; Compare the current scanline to the first scanline of VBlank jr c, .waitVBlank ; Loop as long as the carry flag is set ld a, 0 ; Once we exit the loop we're safely in VBlank ldh [rLCDC], a ; Disable the LCD (must be done during VBlank to protect the LCD)
; Copy our tiles to VRAM ld hl, TileData ; Load the source address of our tiles into HL ld de, STARTOF(VRAM); Load the destination address in VRAM into DE ld b, 2 * TILE_SIZE ; Load the number of bytes to copy into B (2 * 16).copyLoop ld a, [hl] ; Load a byte from the address HL points to into the register A ld [de], a ; Load the byte in the A register to the address DE points to inc hl ; Increment the source pointer in HL inc de ; Increment the destination pointer in DE dec b ; Decrement the loop counter in B jr nz, .copyLoop ; If B isn't zero, continue looping
; This code writes 1 for our tile, and then fills the rest of the tilemap with zero ld hl, TILEMAP0 ; Point HL to the first byte of the tilemap ($9800) ld [hl], 1 ; Load one into the first byte of the tilemap, as pointed to by HL inc hl ; Increment the destination pointer in HL
ld bc, TILEMAP1-TILEMAP0-1 ; Load the size of the remaining tilemap into BC (32x32=1024, or $400, minus 1) ld d, 0 ; Load the value to fill the rest of the tilemap with into D.clearLoop ld [hl], d ; Load the value in D into the location pointed to by HL inc hl ; Increment the destination pointer in HL dec bc ; Decrement the loop counter in BC ld a, b ; Load the value in B into A or c ; Logical OR the value in A (from B) with C jr nz, .clearLoop ; If B and C are both zero, OR C will be zero, otherwise keep looping
; Setup palettes and scrolling ld a, %11100100 ; Define a 4-shade palette from darkest (11) to lightest (00) ldh [rBGP], a ; Set the background palette
ld a, 0 ; Load zero into the register A ldh [rSCX], a ; Set the background scroll registers to show the top-left ldh [rSCY], a ; corner of the background in the top-left corner of the screen
; Combine flag constants defined in hardware.inc into a single value with logical ORs and load it into A ; Note that some of these constants (LCDC_OBJ_OFF, LCDC_WIN_OFF) are zero, but are included for clarity ld a, LCDC_ON | LCDC_BLOCK01 | LCDC_BG_ON | LCDC_OBJ_OFF | LCDC_WIN_OFF ldh [rLCDC], a ; Enable and configure the LCD to show the background
LoopForever: jr LoopForever ; Loop forever
; Our tile data in 2bpp planar format (https://gbdev.io/pandocs/Tile_Data.html)TileData:.empty ; The empty tile is just a zero byte repeated 16 times, so we use REPT to simplify this REPT TILE_SIZE db $00 ENDR.block ; For the block tile we'll use a more verbose syntax so you can see how the tile is built ; low byte high byte db %00000000, %11111111 ; single row of 8 pixels db %01000010, %10000001 db %00000000, %11111111 db %01000010, %10000001 db %00000000, %11111111 db %01000010, %10000001 db %00000000, %11111111 db %11111111, %11111111