162 lines
2.3 KiB
NASM
162 lines
2.3 KiB
NASM
.p816
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.smart
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.include "macros.inc"
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.include "registers.inc"
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.include "keys.inc"
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.include "header.asm"
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.segment "ZEROPAGE"
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nmi_count: .res 2
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.segment "CODE"
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VRAM_CHARS = $0000
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VRAM_BG1 = $1000
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start:
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.include "init.asm"
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; Set up the color palette
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stz CGADD
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; Color 0 - black
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lda #$00
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sta CGDATA
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lda #$00
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sta CGDATA
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; Color 1 - red
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lda #$1f
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sta CGDATA
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lda #$00
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sta CGDATA
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; Color 2 - green
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lda #$e0
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sta CGDATA
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lda #$03
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sta CGDATA
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; Color 3 - blue
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lda #$00
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sta CGDATA
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lda #$7c
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sta CGDATA
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; Graphics mode 0, 8x8 tiles
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stz BGMODE
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; Set BG1 and tile map and character data
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lda #>VRAM_BG1
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sta BG1SC
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lda #VRAM_CHARS
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sta BG12NBA
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; Load character data into VRAM
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lda #$80
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sta VMAIN
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ldx #VRAM_CHARS
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stx VMADDL
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; Set DMA source flags
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lda #%00000001
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sta DMAP0
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; DMA destination VMDATAL register
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lda #<VMDATAL
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sta BBAD0
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; Set starting address to charset
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ldx #.loword(charset)
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stx A1T0L
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lda #^charset
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sta A1B0
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; Write to charset_end bytes
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ldx #(charset_end - charset)
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stx DAS0L
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; actually kick off the DMA
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lda #1
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sta MDMAEN
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; @charset_loop:
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; lda charset,x
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; sta VMDATAL
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; inx
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; lda charset,x
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; sta VMDATAH
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; inx
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; cpx #(charset_end - charset)
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; bne @charset_loop
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; Manually clear screen
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ldx #(VRAM_BG1)
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@loop:
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stx VMADDL
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lda #$00
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sta VMDATAL
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stz VMDATAH
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inx
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cpx #(VRAM_BG1 + 32 * 29)
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bne @loop
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; write tile to position (1, 1)
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TILE_X = 1
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TILE_Y = 1
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ldx #(VRAM_BG1 + (TILE_Y * 32) + TILE_X)
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stx VMADDL
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lda #$01 ; tile number
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sta VMDATAL
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stz VMDATAH
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; Show bg1
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lda #%00000001
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sta TM
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lda #$0f
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sta INIDISP
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lda #%10000001
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sta NMITIMEN
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mainloop:
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lda nmi_count
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nmi_check:
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wai
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cmp nmi_count
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beq nmi_check
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lda JOY1L
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bit #JOYL_L
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beq down_not_pressed
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; write tile 2 to position (4, 8)
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TILE_X2= 4
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TILE_Y2= 8
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ldx #(VRAM_BG1 + (TILE_Y2* 32) + TILE_X2)
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stx VMADDL
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lda #$02
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sta VMDATAL
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stz VMDATAH
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down_not_pressed:
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bra mainloop
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busywait:
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bra busywait
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nmi:
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bit RDNMI
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inc nmi_count
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_rti:
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rti
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.include "charset.asm"
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