snes-asm/test_gfx.asm

.include "header.inc"
.include "snes_init.asm"
.include "my_custom.asm"

.BANK 0 SLOT 0
.org 0
.section "Vblank"

VBlank:
    rti

.ENDS

.BANK 0 SLOT 0
.ORG 0
.section "Main"

.MACRO Video_Port_Control
    ;VRAM transfer, word-access, increment by 1
    lda #%10000000 
    sta $2115
.ENDM

;assumes 8-bit a, 16-bit xy
.MACRO Load_Block_to_VRAM ARGS SOURCE DEST SIZE
    Video_Port_Control

    ldx #DEST
    stx $2116 ; $2116/2117 is 2byte address for VRAM upload/download. most significant bit must be 0 

    lda #:SOURCE ; source bank
    ldx #SOURCE ; source offset
    ldy #SIZE

    stx $4302 ; store data offset into DMA control register
    sta $4304 ; store bank into DMA source bank
    sty $4305 ; store size of block

    lda #$01  
    sta $4300  ; set DMA mode (word, normal increment)

    lda #$18
    sta $4301 ; set destination register (VRAM write register) - add value to $2100 to get destination address
              ; i.e. this is writing to $2118, which when written writes a byte to VRAM

    lda #$01
    sta $420b ; and start the transfer
.ENDM

Start:
    Snes_Init

    Set_A_8_XY_16

    Load_Palette_Color $00, $00
    Load_Palette_Color $00, $00
    Load_Palette_Color $00, $00
    Load_Palette_Color $ff, $0a

    Set_Screen_Brightness %00001111

    lda #%00000000 ; 8x8 for all 4 backgrounds,  no priority flip, Mode: 4 colors/tile w/ 32 palettes
    sta $2105      ; store to screen mode register

    ; size (last argument) depends on color mode
    ; location is beginning of VRAM
    Load_Block_to_VRAM Tiles, $0000, (8*2*2),

    ; put character data at VRAM $0000, tile data at $0400
    lda #$04
    sta $2107 ; BG1 tile map location (upper 6 bits)
    lda #$00
    sta $210b ; BG1 character location ($1000 word intervals - can't go over $8000 b/c size of VRAM)

    ; main screen designation
    lda #%00000001
    sta $212c ; enable bkg 1,

    ldx #$0400 ; load $0400 (VRAM address of tile data)
TileLoadLoop:

    stx $2116  ; store VRAM address of tile data to VRAM address word-sized register

    lda #$01   ; smile tile
    sta $2118  ;store tile map entry to the address specified in $2116 - this increments or not based on 2115

    inx
    stx $2116

    lda #$00 ; blank tile
    sta $2118

    inx

    cpx #$0780 ; $400 - $780 seems to be limit of snes screen tile memory
    bne TileLoadLoop


lda #%10000001  ; enable NMI and joypads
sta $4200

mainloop:
    Spin_Loop $02

    Reset_Palette_Offset
    Load_Palette_Color $00, $00
    Load_Palette_Color $00, $00
    Load_Palette_Color $00, $00
    Load_Palette_Color $ff, $0a

    Spin_Loop $02

    Reset_Palette_Offset
    Load_Palette_Color $ff, $a0
    Load_Palette_Color $00, $00
    Load_Palette_Color $00, $00
    Load_Palette_Color $ff, $0a

    jmp mainloop

.ENDS


.BANK 1 SLOT 0
.org 0
.section "TileData"

Tiles:

;blank tile
    .db $00, $00, $00, $00, $00, $00, $00, $00
    .db $00, $00, $00, $00, $00, $00, $00, $00

;face
    .db %00000000
    .db %00000000

    .db %11000011
    .db %11000011

    .db %11000011
    .db %11000011

    .db %00111000
    .db %00111000

    .db %00111000
    .db %00111000

    .db %10000001
    .db %10000001

    .db %01000010
    .db %01000010

    .db %00111100
    .db %00111100

.ENDS