2015-03-22 01:31:44 +00:00
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;------------------------------------------------------------------------------
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; Let's try to recreate a bit of a level from Mario 2
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;
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;;;;
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; Create an iNES header
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.ines {"prog": 1, "char": 1, "mapper": 0, "mirror": 0}
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;;;;
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; Include all the symbols in the nes library
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.inc <nes.sym>
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;;;;
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; Open the prog section bank 0
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.segment prog 0
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;;;;
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; Current horizontal scroll value
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.org $0000
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.space horizontal_scroll 1
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;;;;
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; Setup the interrupt vectors
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.org $FFFA
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.dw vblank
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.dw main
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.dw irq
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;;;;
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; Here is our code entry point, which we'll call main.
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.org $C000
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.scope main
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; Disable interrupts and decimal flag
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sei
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cld
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; Wait for 2 vblanks
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wait_vb1:
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lda nes.ppu.status
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bpl wait_vb1
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wait_vb2:
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lda nes.ppu.status
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bpl wait_vb2
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; Now we want to initialize the hardware to a known state
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lda #$00
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ldx #$00
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clear_segments:
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sta $00, x
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sta $0100, x
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sta $0200, x
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sta $0300, x
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sta $0400, x
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sta $0500, x
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sta $0600, x
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sta $0700, x
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inx
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bne clear_segments
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; Reset the stack pointer
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ldx #$FF
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txs
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; Disable all graphics and vblank nmi
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lda #$00
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2015-03-22 22:52:13 +00:00
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sta nes.ppu.control
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sta nes.ppu.mask
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2015-03-22 01:31:44 +00:00
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; Call subroutines to initialize the graphics
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jsr load_palette
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jsr load_name_tables
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jsr init_scrolling
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jsr init_ppu
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; Resume interrupts and loop here forever
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cli
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forever:
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jmp forever
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.
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;;;;
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2015-03-22 22:52:13 +00:00
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; nes.ppu.control: bitpattern is VPHB SINN
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; V: NMI enable
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; P: PPU master/slave (this does nothing on the NES)
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; H: Sprite height 0 = 8x8, 1 = 8x16
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; B: Background pattern table address (0: $0000; 1: $1000)
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; S: Sprite pattern table address for 8x8 sprites (0: $0000; 1: $1000; ignored in 8x16 mode)
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; I: VRAM address increment per CPU read/write of nes.vram.io (0: add 1, going across; 1: add 32, going down)
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; NN: Base nametable address (0 = $2000; 1 = $2400; 2 = $2800; 3 = $2C00)
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;
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; Equivalently, bits 0 and 1 are the most significant bit of the scrolling coordinates
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;
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; nes.ppu.mask: bitpattern is BGRs bMmG
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; BGR: Color emphasis bits
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; s: Sprite enable
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; b: Background enable
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; M: Background left column enable
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; m: Sprite left column enable
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; G: Greyscale
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;
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2015-03-22 01:31:44 +00:00
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.scope init_ppu
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2015-03-22 22:52:13 +00:00
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lda #%10001000 ; NMI enable, 8x8 tile, Background: $0000, Sprites: $1000, Address increment: 1, Nametable: $2000
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sta nes.ppu.control
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lda #%00011110 ; No color emphasis, Enable sprites, Enable Background, Enable sprite and bg left column, no greyscale
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sta nes.ppu.mask
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2015-03-22 01:31:44 +00:00
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rts
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.
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;;;;
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; This initializes the scrolling value in the zero page
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; So that we begin offscreen and can scroll down
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.scope init_scrolling
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lda #$00
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sta horizontal_scroll zp
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rts
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.
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;;;;
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; Load palette into $3F00
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.scope load_palette
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lda #$3F
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ldx #$00
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sta nes.vram.address
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stx nes.vram.address
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loop:
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lda palette, x
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sta nes.vram.io
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inx
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cpx #$20
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bne loop
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rts
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.
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;;;;
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; Load the background tiles into the name table
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.scope load_name_tables
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ldy #$00
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ldx #$04
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lda #<background
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sta $10
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lda #>background
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sta $11
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lda #$24
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sta nes.vram.address
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lda #$00
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sta nes.vram.address
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loop:
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lda ($10), y
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sta nes.vram.io
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iny
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bne loop
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inc $11
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dex
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bne loop
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; Now clear the second nametable
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ldy #$00
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ldx #$04
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lda #$00
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.scope
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loop:
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sta nes.vram.io
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iny
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bne loop
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dex
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bne loop
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rts
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;;;;
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; Scroll the screen if we have to
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.scope scroll_screen
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ldx #$00 ; Reset VRAM Address to $0000
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stx nes.vram.address
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stx nes.vram.address
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ldx horizontal_scroll zp
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inx
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stx horizontal_scroll zp
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lda #$00
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stx nes.ppu.scroll ; Write the new horizontal scroll value
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sta nes.ppu.scroll ; Write 0 for vertical scroll
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rts
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.
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;;;;
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; VBlank routine
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.scope vblank
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jsr scroll_screen
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rti
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.
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.scope irq
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rti
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.
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;;;;
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; Here is a bg palette which I ripped from Mario 2, but, I just put black for sprite palette
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palette:
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.bytes $21, $30, $12, $0F, $21, $30, $16, $0F, $21, $27, $17, $0F, $21, $29, $1A, $0F
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.bytes $0F, $0F, $0F, $0F, $0F, $0F, $0F, $0F, $0F, $0F, $0F, $0F, $0F, $0F, $0F, $0F
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;;;;
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; This is the background tile map, or "Name Table" for a bit of a Mario 2 Level.
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; Here is how I generated this from a string of hex
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; ary.map{|byte| "$%.2X" % byte.to_i(16) }.each_slice(32){|group| puts ".bytes #{group.join(', ')}" }
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background:
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $BA, $BC, $FA, $FA, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $BB, $BD, $FA, $FA, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $BA, $BC, $FA, $FA, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $BB, $BD, $FA, $FA, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $BA, $BC, $FA, $FA, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $BB, $BD, $FA, $FA, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $BA, $BC, $FA, $FA, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $BB, $BD, $FA, $FA, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $BA, $BC, $FA, $FA, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $BB, $BD, $FA, $FA, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $BA, $BC, $FA, $FA, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $B0, $B1, $B0, $B1, $90, $91, $FA, $FA, $FA, $FA
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.bytes $B4, $B6, $B8, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $60, $62, $64, $62, $64, $62, $64, $62, $64, $66, $FA, $FA
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.bytes $B5, $B7, $B9, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $46, $63, $65, $63, $65, $63, $65, $63, $65, $67, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $61, $63, $65, $63, $65, $63, $65, $63, $65, $67, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $61, $63, $65, $63, $65, $63, $65, $63, $65, $67, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $DE, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $61, $63, $65, $63, $65, $63, $65, $63, $65, $67, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $61, $63, $65, $63, $65, $63, $65, $63, $65, $67, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $61, $63, $65, $63, $65, $63, $65, $63, $65, $67, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $61, $63, $65, $63, $65, $63, $65, $63, $65, $67, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $61, $63, $65, $63, $65, $63, $65, $63, $65, $67, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $61, $63, $65, $63, $65, $63, $65, $63, $65, $67, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $61, $63, $65, $63, $65, $63, $65, $63, $65, $67, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $61, $63, $65, $63, $65, $63, $65, $63, $65, $67, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $61, $63, $65, $63, $65, $63, $65, $63, $65, $67, $FA, $FA
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.bytes $FA, $FA, $FA, $FA, $FA, $FA, $B0, $B1, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $FA, $61, $63, $65, $63, $65, $63, $65, $63, $65, $67, $FA, $FA
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.bytes $70, $72, $70, $72, $70, $72, $70, $72, $70, $72, $70, $72, $70, $72, $70, $72, $70, $72, $70, $72, $70, $72, $70, $72, $70, $72, $70, $72, $70, $72, $70, $72
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.bytes $71, $73, $71, $73, $71, $73, $71, $73, $71, $73, $71, $73, $71, $73, $71, $73, $71, $73, $71, $73, $71, $73, $71, $73, $71, $73, $71, $73, $71, $73, $71, $73
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.bytes $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF
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.bytes $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AE, $AE, $AE, $AE, $AE, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF, $AE, $AF
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.bytes $55, $55, $55, $55, $33, $44, $DD, $DD, $57, $55, $55, $55, $33, $44, $DD, $DD, $55, $55, $55, $55, $33, $44, $DD, $DD, $50, $55, $55, $55, $CC, $FF, $FF, $FF
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.bytes $55, $55, $55, $54, $FF, $FF, $FF, $FF, $55, $55, $55, $55, $33, $FF, $FF, $FF, $F5, $F5, $F5, $F5, $F3, $FF, $FF, $FF, $5A, $5A, $5A, $5A, $0A, $0A, $0A, $0A
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;;;;
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2015-03-22 17:53:45 +00:00
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; Here we include an entire binary char rom from Mario 2, which contains 4KB of tile data
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; No spirte data is included.
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2015-03-22 01:31:44 +00:00
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.segment char 0
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.org $0000
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.incbin "mario2.char"
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