SUCCESS!

Have successfully written a background tile to screen!

my_custom.asm

@@ -21,6 +21,11 @@ lvl3\@:
     bne lvl3\@
 .ENDM
 
+.MACRO Set_A_8_XY_16
+; 16-bit xy, 8-bit a
+rep #%00010000
+sep #%00100000
+.ENDM
 
 .MACRO Reset_Palette_Offset
 stz $2121
@@ -37,6 +42,6 @@ sta $2122
 
 .MACRO Set_Screen_Brightness
 lda #\1
-sta $2100
+sta $2100 ; $2100 is the screen brightness register
 
 .ENDM

register_notes

@@ -4,10 +4,10 @@ $2100 - screen on/off + brightness
 
 $2105 - screen format register, changes size of tiles
 
+$2107 - set starting tilemap location
 
 $2121 - stores the index into CGRAM to write a color value via $2122
 
-
 $2122 - write a 2-byte SNES color value to the CGRAM. this auto-increments after writing,
 which is why $2121 needs to be written to reset this. it's common to write `stz $2121`
 

test_gfx.asm

@@ -15,26 +15,74 @@ VBlank:
 .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
 
-; 16-bit xy, 8-bit a
+    Set_A_8_XY_16
-rep #%00010000
-sep #%00100000
-
-; Load palette by writing to $2122
-; .db $00, $00, $E0, $7F, $1F, $00, $FF, $03
 
     Load_Palette_Color $00, $00
     Load_Palette_Color $00, $00
     Load_Palette_Color $00, $00
     Load_Palette_Color $ff, $0a
 
-;lda #%00000
-
-
     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 Face, $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)
+    stx $2116  ; and store it to  VRAM address word-sized register
+
+    ldx #$0001
+    stx $2118  ;store tile map entry to the address specified in $2116 - this eincrements or not based on 2105
+
+
 lda #%10000001  ; enable NMI and joypads
 sta $4200
 
@@ -65,6 +113,10 @@ mainloop:
 .section "TileData"
 
 Face:
+
+    .db $00, $00, $00, $00, $00, $00, $00, $00
+    .db $00, $00, $00, $00, $00, $00, $00, $00
+
     .db %00000000
     .db %00000000