snes-asm/homebrew-tutorial/main.asm

137 lines
1.9 KiB
NASM
Raw Normal View History

2022-06-13 16:00:17 -07:00
.p816
.smart
.include "macros.inc"
.include "registers.inc"
2022-06-16 13:40:58 -07:00
.include "keys.inc"
2022-06-13 16:00:17 -07:00
.include "header.asm"
2022-06-16 14:33:46 -07:00
.segment "ZEROPAGE"
nmi_count: .res 2
2022-06-13 16:00:17 -07:00
.segment "CODE"
2022-06-13 17:09:27 -07:00
VRAM_CHARS = $0000
VRAM_BG1 = $1000
2022-06-13 16:00:17 -07:00
start:
.include "init.asm"
; Set up the color palette
stz CGADD
2022-06-13 17:09:27 -07:00
; Color 0 - black
lda #$00
sta CGDATA
lda #$00
sta CGDATA
; Color 1 - red
lda #$1f
2022-06-13 17:09:27 -07:00
sta CGDATA
lda #$00
2022-06-13 17:09:27 -07:00
sta CGDATA
2022-06-15 11:06:47 -07:00
; Color 2 - green
2022-06-13 17:09:27 -07:00
lda #$e0
2022-06-13 16:00:17 -07:00
sta CGDATA
2022-06-13 16:00:41 -07:00
lda #$03
2022-06-13 16:00:17 -07:00
sta CGDATA
2022-06-15 11:06:47 -07:00
; Color 3 - blue
2022-06-13 17:09:27 -07:00
lda #$00
sta CGDATA
lda #$7c
sta CGDATA
; Graphics mode 0, 8x8 tiles
stz BGMODE
; Set BG1 and tile map and character data
lda #>VRAM_BG1
sta BG1SC
lda #VRAM_CHARS
sta BG12NBA
; Load character data into VRAM
lda #$80
sta VMAIN
ldx #VRAM_CHARS
stx VMADDL
@charset_loop:
lda charset,x
sta VMDATAL
inx
lda charset,x
sta VMDATAH
inx
cpx #(charset_end - charset)
bne @charset_loop
; Manually clear screen
ldx #(VRAM_BG1)
@loop:
stx VMADDL
2022-06-15 11:10:07 -07:00
lda #$00
2022-06-15 11:08:30 -07:00
sta VMDATAL
stz VMDATAH
inx
cpx #(VRAM_BG1 + 32 * 29)
bne @loop
2022-06-13 17:09:27 -07:00
; write tile to position (1, 1)
TILE_X = 1
TILE_Y = 1
ldx #(VRAM_BG1 + (TILE_Y * 32) + TILE_X)
stx VMADDL
lda #$01 ; tile number
sta VMDATAL
stz VMDATAH
; Show bg1
lda #%00000001
sta TM
2022-06-13 16:00:17 -07:00
lda #$0f
sta INIDISP
2022-06-16 14:33:46 -07:00
lda #%10000001
2022-06-15 11:30:27 -07:00
sta NMITIMEN
mainloop:
2022-06-16 14:33:46 -07:00
lda nmi_count
nmi_check:
wai
cmp nmi_count
beq nmi_check
2022-06-16 13:40:58 -07:00
lda JOY1L
bit #JOYL_L
2022-06-15 11:30:27 -07:00
beq down_not_pressed
; write tile 2 to position (4, 8)
TILE_X2= 4
TILE_Y2= 8
ldx #(VRAM_BG1 + (TILE_Y2* 32) + TILE_X2)
stx VMADDL
lda #$02
sta VMDATAL
stz VMDATAH
down_not_pressed:
bra mainloop
2022-06-13 16:00:17 -07:00
busywait:
bra busywait
nmi:
bit RDNMI
2022-06-16 14:33:46 -07:00
inc nmi_count
2022-06-13 16:00:17 -07:00
_rti:
rti
2022-06-13 17:09:27 -07:00
.include "charset.asm"