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fullbg.asm
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fullbg.asm
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.include "settings.inc"
.include "constants.inc"
.bank 0, 16, $c000, "NES_PRG0"
;;;;;;;;;;;;;;
.segment "ROData"
.org $E000
palette:
.byte $22,$29,$1a,$0f, $22,$36,$17,$0f, $22,$30,$21,$0f, $22,$27,$17,$0f ;;background palette
.byte $0F,$2C,$25,$24, $0F,$02,$38,$3C, $0F,$1C,$15,$14, $0F,$02,$38,$3C ;;sprite palette
end_palette:
s_palette = (end_palette - palette)
rosprites:
;vert tile attr horiz
.byte $80, $32, $00, $80 ;sprite 0
.byte $80, $33, $00, $88 ;sprite 1
.byte $88, $34, $00, $80 ;sprite 2
.byte $88, $35, $00, $88 ;sprite 3
end_rosprites:
s_rosprites = (end_rosprites - rosprites)
background:
.storage $20, $24 ;;row 1, all sky -- This row is discarded
.byte $24, $f4, $f6, $f6, $f6, $f6, $f6, $f6, $f6, $f6, $f7, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24
.byte $24, $f8, $1c, $1e, $19, $24, $1d, $12, $16, $2b, $f8, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24
.byte $24, $f8, $24, $24, $24, $24, $24, $24, $24, $24, $f8, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24
.byte $24, $f8, $24, $24, $24, $24, $24, $24, $fd, $fe, $f8, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24
.byte $24, $f8, $24, $24, $24, $24, $24, $24, $24, $24, $f8, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24
.byte $24, $f5, $f6, $f6, $f6, $f6, $f6, $f6, $f6, $f6, $f9, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24, $24
;.storage $F0, $24
end_background:
s_background = (end_background - background)
attribute:
.byte %00000000, %00010000, %01010000, %00010000, %00000000, %00000000, %00000000, %00110000
end_attribute:
s_attribute = (end_attribute - attribute)
bg_addr_lo .lobyte background
bg_addr_hi .hibyte background
;;;;;;;;;;;;;;
.segment "Code"
.org $C000
; Zero page data
p_lo = $00
p_hi = $01
.function IRQ
RTI
.endfunction
.function VBLANKWAIT
BIT PPUSTATUS
BPL VBLANKWAIT
.endfunction
.function LOAD_BG
LDA #%10010000 ; enable nmi, sprites from pattern table 0, background from pattern table 1
STA PPUCTRL
LDA bg_addr_lo
STA p_lo
LDA bg_addr_hi
STA p_hi
LDA PPUSTATUS ; read ppu status to reset the high/low latch
LDA #$20
STA PPUADDR ; write the high byte of $2000 address
LDA #$00
STA PPUADDR ; write the low byte of $2000 address
LDX #$00
LDY #$00 ; start out at 0, 0
loadbgloop:
loadlineloop:
LDA (p_lo), y ; load data from address (background + the value in y)
STA PPUDATA ; write to ppu
INY ; y = y + 1
CPY #$00 ; compare y to background size
BNE loadlineloop ; repeat until all bytes copied on this line
INC p_hi
INX
CPX #$04
BNE loadbgloop
.endfunction
.function RESET
SEI ; disable IRQs
CLD ; disable decimal mode
LDX #$40
STX APUIRQ ; disable APU frame IRQ
LDX #$FF
TXS ; Set up stack
INX ; now X = 0
STX PPUCTRL ; disable NMI
STX PPUMASK ; disable rendering
STX DPMCIRQ ; disable DMC IRQs
VBLANKWAIT()
clrmem:
LDA #$00
STA $0000, x
STA $0100, x
STA $0200, x
STA $0400, x
STA $0500, x
STA $0600, x
STA $0700, x
LDA #$FE
STA $0300, x
INX
BNE clrmem
VBLANKWAIT() ; Second wait for vblank, PPU is ready after this
loadpalettes:
LDA PPUSTATUS ; read ppu status to reset the high/low latch
LDA #$3f
STA PPUADDR ; write the high byte of $3f00 address
LDA #$00
STA PPUADDR ; write the low byte of $3f00 address
LDX #$00 ; start out at 0
loadpalettesloop:
LDA palette, x ; load data from address (palette + the value in x)
STA PPUDATA ; write to ppu
INX ; x = x + 1
CPX #s_palette ; compare x to palette size
BNE loadpalettesloop ; repeat until all bytes loaded
LOAD_BG()
loadattribute:
LDA PPUSTATUS ; read ppu status to reset the high/low latch
LDA #$23
STA PPUADDR ; write the high byte of $23c0 address
LDA #$c0
STA PPUADDR ; write the low byte of $23c0 address
LDX #$00 ; start out at 0
loadattributeloop:
LDA attribute, x ; load data from address (attribute + the value in x)
STA PPUDATA ; write to ppu
INX ; x = x + 1
CPX #s_attribute ; compare x to hex $08, decimal 8 - copying 8 bytes
BNE loadattributeloop ; branch to loadattributeloop if compare was not equal to zero
; if compare was equal to 128, keep going down
LDA #%10010000 ; enable nmi, sprites from pattern table 0, background from pattern table 1
STA PPUCTRL
LDA #%00011110 ; enable sprites, enable background, no clipping on left side
STA PPUMASK
LDA #$00 ;;tell the ppu there is no background scrolling
STA PPUSCROLL
sta PPUSCROLL
forever:
JMP forever ;jump back to forever, infinite loop
.endfunction
.function NMI
LDA #$00
STA OAMADDR ; set the low byte (00) of the ram address
LDA #$02
STA OAMDMA ; set the high byte (02) of the ram address, start the transfer
LDA #%10010000 ; enable nmi, sprites from pattern table 0, background from pattern table 1
STA PPUCTRL
LDA #%00011110 ; enable sprites, enable background, no clipping on left side
STA PPUMASK
LDA #$00 ;;tell the ppu there is no background scrolling
STA PPUSCROLL
STA PPUSCROLL
RTI
.endfunction
;;;;;;;;;;;;;;
;.bank 1, 16, $FFFA, "NES_PRG1"
.segment "Vectors"
.org $FFFA ;first of the three vectors starts here
.word NMI ;when an NMI happens (once per frame if enabled) the
;processor will jump to the label NMI:
.word RESET ;when the processor first turns on or is reset, it will jump
;to the label RESET:
.word IRQ ;external interrupt IRQ is not used in this tutorial
;;;;;;;;;;;;;;
.bank 1, 8, $0000, "NES_CHR0"
.segment "Chr"
.org $0000
.incbin "mario.chr" ;includes 8KB graphics file from SMB1