;;;; ; Create an iNES header .ines {"prog": 1, "char": 1, "mapper": 0, "mirror": 0} ;;;; ; Here is a good spot to associate zero page memory addresses ; with quick access variables in the program. .org $0200 sprite: ;;;; ; Setup the interrupt vectors .org $FFFA .dw vblank .dw main .dw irq .org $C000 ;;;; ; Here is our code entry point, which we'll call main. main: ; Disable interrupts and decimal flag sei cld ; Wait for 2 vblanks wait_vb1: lda $2002 bpl wait_vb1 wait_vb2: lda $2002 bpl wait_vb2 ; Now we want to initialize the hardware to a known state lda #$00 ldx #$00 clear_segments: sta $00, X sta $0100, X sta $0200, X sta $0300, X sta $0400, X sta $0500, X sta $0600, X sta $0700, X inx bne clear_segments ; Reset the stack pointer ldx #$FF txs ; Disable all graphics. lda #$00 sta $2000 sta $2001 jsr init_graphics jsr init_input jsr init_sound jsr init_ppu ; Resume interrupts and loop here forever cli forever: jmp forever ;;;; ; Set basic PPU registers. Load background from $0000, ; sprites from $1000, and the name table from $2000. init_ppu: lda #$88 sta $2000 lda #$1E sta $2001 rts ;;;; ; Initialize all the sprites, palettes, nametables, and scrolling init_graphics: jsr init_sprites jsr load_palette jsr load_name_tables jsr init_scrolling rts ;;;; ; Initialize the controller input, keeping track of the A button init_input: lda #$00 sta $01 ; $01 = A button rts init_sound: ; initialize sound hardware lda #$01 sta $4015 lda #$00 sta $4001 lda #$40 sta $4017 rts init_sprites: ; Clear page #2, which we'll use to hold sprite data lda #$00 ldx #$00 sprite_clear1: sta sprite, x inx bne sprite_clear1 ; initialize Sprite 0 lda #$70 sta $0200 ; sprite Y coordinate lda #$01 sta $0201 ; sprite + 1Pattern number sta $0203 ; sprite+3 X coordinate ; sprite+2, color, stays 0. ; Set initial value of dx lda #$01 sta $00 ; dx = $00 ; Set initial value of dy lda #$70 sta $03 ; dy = $03 rts ; Load palette into $3F00 load_palette: lda #$3F ldx #$00 sta $2006 stx $2006 loady_loop: lda palette, X sta $2007 inx cpx #$20 bne loady_loop rts ; Jam some text into the first name table (at $2400, thanks to mirroring) load_name_tables: ldy #$00 ldx #$04 lda #bg sta $11 lda #$24 sta $2006 lda #$00 sta $2006 go_back: lda ($10), Y sta $2007 iny bne go_back inc $11 dex bne go_back rts ; Clear out the Name Table at $2800 (where we already are. Yay.) ldy #$00 ldx #$04 lda #$00 back: sta $2007 iny bne back dex bne back rts init_scrolling: lda #$F0 sta $02 ; scroll rts update_sprite: lda #>sprite sta $4014 ; Jam page $200-$2FF into SPR-RAM lda $0203 ; sprite+3 Is this right??? beq hit_left cmp #$F7 bne edge_done ; Hit right ldx #$FF stx $00 ; dx jsr high_c jmp edge_done hit_left: ldx #$01 stx $00 ; dx jsr high_c edge_done: ; update X and store it. clc adc $00 ; dx sta $0203 ; sprite+3 Is this right? rts react_to_input: lda #$01 ; strobe joypad sta $4016 lda #$00 sta $4016 lda $4016 ; Is the A button down? AND #$01 beq not_a ldx $01 ; a bne a_done ; Only react if the A button wasn't down last time. sta $01 ; Store the 1 in local variable 'a' so that we this is jsr reverse_dx ; only called once per press. jmp a_done not_a: sta $01 ; A has been released, so put that zero into 'a'. a_done: lda $4016 ; B does nothing lda $4016 ; Select does nothing lda $4016 ; Start does nothing lda $4016 ; Up and #$01 beq not_up ldx sprite ; Load Y value cpx #$07 beq not_up ; No going past the top of the screen dex stx sprite not_up: lda $4016 ; Down and #$01 beq not_dn ldx sprite cpx #$DF ; No going past the bottom of the screen. beq not_dn inx stx sprite not_dn: rts ; Ignore left and right, we don't use 'em reverse_dx: lda #$FF eor $00 ; dx clc adc #$01 sta $00 ; dx jsr low_c rts scroll_screen: ldx #$00 ; Reset VRAM stx $2006 stx $2006 ldx $02 ; scroll ; Do we need to scroll at all? beq no_scroll dex stx $02 ; scroll lda #$00 sta $2005 ; Write 0 for Horiz. Scroll value stx $2005 ; Write the value of 'scroll' for Vert. Scroll value no_scroll: rts low_c: pha lda #$84 sta $4000 lda #$AA sta $4002 lda #$09 sta $4003 pla rts high_c: pha lda #$86 sta $4000 lda #$69 sta $4002 lda #$08 sta $4003 pla rts vblank: jsr scroll_screen jsr update_sprite jsr react_to_input irq: rti ; palette data palette: .bytes $0E,$00,$0E,$19,$00,$00,$00,$00,$00,$00,$00,$00,$01,$00,$01,$21 .bytes $0E,$20,$22,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00 ; Background data bg: .ascii " " .ascii " " .ascii " SAF'S 6502 NES ASSEMBLER " .ascii " " .ascii " " .ascii " " .ascii " VSS RES " .ascii " RDY PHI2 " .ascii " PH1 S0 " .ascii " IRQ 6 PHI0 " .ascii " NC NC " .ascii " NMI NC " .ascii " SYNC 5 R/W " .ascii " VCC D0 " .ascii " A0 D1 " .ascii " A1 0 D2 " .ascii " A2 D3 " .ascii " A3 D4 " .ascii " A4 2 D5 " .ascii " A5 D6 " .ascii " A6 D7 " .ascii " A7 A15 " .ascii " A8 A14 " .ascii " A9 A13 " .ascii " A10 A12 " .ascii " A11 VSS " .ascii " " .ascii " " .ascii " " .ascii " " ; Attribute table .bytes $00,$00,$00,$00,$00,$00,$00,$00, .bytes $00,$00,$FF,$FF,$FF,$00,$00,$00, .bytes $00,$00,$FF,$FF,$FF,$00,$00,$00, .bytes $00,$00,$FF,$FF,$FF,$00,$00,$00, .bytes $00,$00,$FF,$FF,$FF,$00,$00,$00, .bytes $00,$00,$FF,$FF,$FF,$00,$00,$00, .bytes $00,$00,$FF,$FF,$FF,$00,$00,$00, .bytes $00,$00,$00,$00,$00,$00,$00,$00, ; This is CHR-ROM page 1, which starts at 0x0000, but I'm skipping the first bit ; So this is where tile memory is going to go, this is the commodore 64's character ROM ; mapped to ASCII for tile numbers. We are only using 4KB of this 8KB page. .org $0200 .bytes $00,$00,$00,$00,$00,$00,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 32 .bytes $18,$18,$18,$18,$00,$00,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 33 .bytes $66,$66,$66,$00,$00,$00,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 34 .bytes $66,$66,$FF,$66,$FF,$66,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 35 .bytes $18,$3E,$60,$3C,$06,$7C,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 36 .bytes $62,$66,$0C,$18,$30,$66,$46,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 37 .bytes $3C,$66,$3C,$38,$67,$66,$3F,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 38 .bytes $06,$0C,$18,$00,$00,$00,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 39 .bytes $0C,$18,$30,$30,$30,$18,$0C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 40 .bytes $30,$18,$0C,$0C,$0C,$18,$30,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 41 .bytes $00,$66,$3C,$FF,$3C,$66,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 42 .bytes $00,$18,$18,$7E,$18,$18,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 43 .bytes $00,$00,$00,$00,$00,$18,$18,$30,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 44 .bytes $00,$00,$00,$7E,$00,$00,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 45 .bytes $00,$00,$00,$00,$00,$18,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 46 .bytes $00,$03,$06,$0C,$18,$30,$60,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 47 .bytes $3C,$66,$6E,$76,$66,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 48 .bytes $18,$18,$38,$18,$18,$18,$7E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 49 .bytes $3C,$66,$06,$0C,$30,$60,$7E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 50 .bytes $3C,$66,$06,$1C,$06,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 51 .bytes $06,$0E,$1E,$66,$7F,$06,$06,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 52 .bytes $7E,$60,$7C,$06,$06,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 53 .bytes $3C,$66,$60,$7C,$66,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 54 .bytes $7E,$66,$0C,$18,$18,$18,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 55 .bytes $3C,$66,$66,$3C,$66,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 56 .bytes $3C,$66,$66,$3E,$06,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 57 .bytes $00,$00,$18,$00,$00,$18,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 58 .bytes $00,$00,$18,$00,$00,$18,$18,$30,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 59 .bytes $0E,$18,$30,$60,$30,$18,$0E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 60 .bytes $00,$00,$7E,$00,$7E,$00,$00,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 61 .bytes $70,$18,$0C,$06,$0C,$18,$70,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 62 .bytes $3C,$66,$06,$0C,$18,$00,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 63 .bytes $3C,$66,$6E,$6E,$60,$62,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 64 .bytes $18,$3C,$66,$7E,$66,$66,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 65 .bytes $7C,$66,$66,$7C,$66,$66,$7C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 66 .bytes $3C,$66,$60,$60,$60,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 67 .bytes $78,$6C,$66,$66,$66,$6C,$78,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 68 .bytes $7E,$60,$60,$78,$60,$60,$7E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 69 .bytes $7E,$60,$60,$78,$60,$60,$60,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 70 .bytes $3C,$66,$60,$6E,$66,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 71 .bytes $66,$66,$66,$7E,$66,$66,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 72 .bytes $3C,$18,$18,$18,$18,$18,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 73 .bytes $1E,$0C,$0C,$0C,$0C,$6C,$38,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 74 .bytes $66,$6C,$78,$70,$78,$6C,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 75 .bytes $60,$60,$60,$60,$60,$60,$7E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 76 .bytes $63,$77,$7F,$6B,$63,$63,$63,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 77 .bytes $66,$76,$7E,$7E,$6E,$66,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 78 .bytes $3C,$66,$66,$66,$66,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 79 .bytes $7C,$66,$66,$7C,$60,$60,$60,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 80 .bytes $3C,$66,$66,$66,$66,$3C,$0E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 81 .bytes $7C,$66,$66,$7C,$78,$6C,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 82 .bytes $3C,$66,$60,$3C,$06,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 83 .bytes $7E,$18,$18,$18,$18,$18,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 84 .bytes $66,$66,$66,$66,$66,$66,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 85 .bytes $66,$66,$66,$66,$66,$3C,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 86 .bytes $63,$63,$63,$6B,$7F,$77,$63,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 87 .bytes $66,$66,$3C,$18,$3C,$66,$66,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 88 .bytes $66,$66,$66,$3C,$18,$18,$18,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 89 .bytes $7E,$06,$0C,$18,$30,$60,$7E,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 90 .bytes $3C,$30,$30,$30,$30,$30,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 91 .bytes $0C,$12,$30,$7C,$30,$62,$FC,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 92 .bytes $3C,$0C,$0C,$0C,$0C,$0C,$3C,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 93 .bytes $00,$18,$3C,$7E,$18,$18,$18,$18,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 94 .bytes $00,$10,$30,$7F,$7F,$30,$10,$00,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; Character 95 ; This is CHR-ROM page 2, which starts at 0x2000, and we put the sprite data here. .org $1000 .bytes $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00 ; Character 0: Blank .bytes $18,$24,$66,$99,$99,$66,$24,$18,$00,$18,$18,$66,$66,$18,$18,$00 ; Character 1: Diamond sprite