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; iNES Header
; .inesprg 1 ; 1x 16KB bank of PRG code
; .ineschr 1 ; 1x 8KB bank of CHR data
; .inesmap 0 ; mapper 0 = NROM, no bank swapping
; .inesmir 1 ; background mirroring (ignore for now)
; $0000-0800 - Internal RAM, 2KB chip in the NES
; $2000-2007 - PPU access ports
; $4000-4017 - Audio and controller access ports
; $6000-7FFF - Optional WRAM inside the game cart
; $8000-FFFF - Game cart ROM
; iNES Header
; The 16 byte iNES header gives the emulator all the information about the game including mapper, graphics mirroring, and PRG/CHR sizes. You can include all this inside your asm file at the very beginning.
.inesprg 1 ; 1x 16KB PRG code
.ineschr 1 ; 1x 8KB CHR data
.inesmap 0 ; mapper 0 = NROM, no bank swapping
.inesmir 1 ; background mirroring
;; DECLARE SOME VARIABLES HERE
.rsset $0000 ;;start variables at ram location 0 in zero page memory
loopCount .rs 1 ; count the loop
playerx .rs 1 ; players x pos
playervx .rs 1 ; players x vel
playery .rs 1 ; players y pos
playervy .rs 1 ; player y vel (negative is up)
controller1 .rs 1 ; controller 1 button vector
gravity .rs 1 ; gravity
ground .rs 1 ; y value of the ground
inAir .rs 1
enemyx .rs 1
enemyy .rs 1
backgroundLo .rs 1
backgroundHi .rs 1
counterLo .rs 1
counterHi .rs 1
scroll .rs 1 ; horizontal scroll count
nametable .rs 1 ; which nametable to use, 0 or 1
columnLow .rs 1 ; low byte of new column address
columnHigh .rs 1 ; high byte of new column address
sourceLow .rs 1 ; source for column data
sourceHigh .rs 1
columnNumber .rs 1 ; which column of level data to draw
;;;;;;;;;;;;;;;
; NES is powererd on
;
.bank 0 ; NESASM arranges things into 8KB chunks, this is chunk 0
.org $C000 ; Tells the assembler where to start in this 8kb chunk
RESET:
SEI ; disable IRQs
CLD ; disable decimal mode, meant to make decimal arithmetic "easier"
LDX #$40
STX $4017 ; disable APU frame IRQ
LDX #$FF
TXS ; Set up stack
INX ; now X = 0
STX $2000 ; disable NMI
STX $2001 ; disable rendering
STX $4010 ; disable DMC IRQs
vblankwait1: ; First wait for vblank to make sure PPU is ready
BIT $2002
BPL vblankwait1
;; Helper to wipe memory
clrmem:
LDA #$00
STA $0000, x
STA $0100, x
STA $0300, x
STA $0400, x
STA $0500, x
STA $0600, x
STA $0700, x
LDA #$FE
STA $0200, x ;move all sprites off screen
INX
BNE clrmem
vblankwait2: ; Second wait for vblank, PPU is ready after this
BIT $2002
BPL vblankwait2
;;;;;;;;;;;;;;;;;;;;;;
; Load game pallets
LoadPalettes:
LDA $2002 ; read PPU status to reset the high/low latch
LDA #$3F ; max out 0011 1111
STA $2006 ; write the high byte of $3F00 address
LDA #$00
STA $2006 ; 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)
; 1st time through loop it will load palette+0
; 2nd time through loop it will load palette+1
; 3rd time through loop it will load palette+2
; etc
STA $2007 ; write to PPU
INX ; X = X + 1
CPX #$20 ; Compare X to hex $10, decimal 16 - copying 16 bytes = 4 sprites
BNE LoadPalettesLoop ; Branch to LoadPalettesLoop if compare was Not Equal to zero
LoadSprites:
LDX #$00 ; start at 0
LoadSpritesLoop:
LDA playersprite, x ; load data from address (sprites + x)
STA $0200, x ; store into RAM address ($0200 + x)
INX ; X = X + 1
CPX #$1C ; Compare X to hex $20, decimal 32
BNE LoadSpritesLoop ; Branch to LoadSpritesLoop if compare was Not Equal to zero
; if compare was equal to 32, keep going down
;; Background is 960 bytes 240 * 4
LoadBackground:
LDA $2002 ; read PPU status to reset the high/low latch
LDA #$20
STA $2006 ; write the high byte of $2000 address
LDA #$00
STA $2006 ; write the low byte of $2000 address
LDX #$00 ; start out at 0
;; we need to copy more that 256
LDA #LOW(background)
STA backgroundLo
LDA #HIGH(background)
STA backgroundHi
;; 960 bytes = $03C0
LDA #$C0;
STA counterLo
LDA #$03
STA counterHi
LDY #$00; keep y zero, we jut need y to be init to 0 for indirect index mode to work in the square bracket
LoadBackgroundLoop:
LDA [backgroundLo], y ; load data from background
STA $2007 ; write to PPU data port to copy to background data
LDA backgroundLo ; load the low byte of the background address into A
CLC ; clear the carry bit
ADC #$01 ; add 1 to A
STA backgroundLo ; store A back into the mem addr
LDA backgroundHi ; load the high byte of the background address into A
ADC #$00 ; add 0, but if there is a carry (overflow) add 1
STA backgroundHi ; inc poitner to the next byte if necessary
LDA counterLo ; load the counter low byte
SEC ; set cary flag
SBC #$01 ; subtract with carry by 1
STA counterLo ; store the low byte of the counter
LDA counterHi ; load the high byte
SBC #$00 ; sub 0, but there is a carry
STA counterHi ; decrement the loop counter
LDA counterLo ; load the low byte
CMP #$00 ; see if it is zero, if not loop
BNE LoadBackgroundLoop
LDA counterHi
CMP #$00 ; see if the high byte is zero, if not loop
BNE LoadBackgroundLoop ; if the loop counter isn't 0000, keep copying
;LDA background, x ; load data from address (background + the value in x)
;STA $2007 ; write to PPU
;INX ; X = X + 1
;CPX #$80 ; Compare X to hex $80, decimal 128 - copying 128 bytes
;BNE LoadBackgroundLoop ; Branch to LoadBackgroundLoop if compare was Not Equal to zero
; if compare was equal to 128, keep going down
LoadAttribute:
LDA $2002 ; read PPU status to reset the high/low latch
LDA #$23
STA $2006 ; write the high byte of $23C0 address
LDA #$C0
STA $2006 ; 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 $2007 ; write to PPU
INX ; X = X + 1
CPX #$40 ; Compare X to hex $40, decimal 64
BNE LoadAttributeLoop ; Branch to LoadAttributeLoop if compare was Not Equal to zero
; if compare was equal to 128, keep going down
; PPUCTRL ($2000)
; 76543210
; | ||||||
; | ||||++- Base nametable address
; | |||| (0 = $2000; 1 = $2400; 2 = $2800; 3 = $2C00)
; | |||+--- VRAM address increment per CPU read/write of PPUDATA
; | ||| (0: increment by 1, going across; 1: increment by 32, going down)
; | ||+---- Sprite pattern table address for 8x8 sprites (0: $0000; 1: $1000)
; | |+----- Background pattern table address (0: $0000; 1: $1000)
; | +------ Sprite size (0: 8x8; 1: 8x16)
; |
; +-------- Generate an NMI at the start of the
; vertical blanking interval vblank (0: off; 1: on)
LDA #%10010000 ; enable NMI, sprites from Pattern Table 0, background from Pattern Table 1
STA $2000
; PPUMASK ($2001)
; binary byte flags
; 76543210
; ||||||||
; |||||||+- Grayscale (0: normal color; 1: AND all palette entries
; ||||||| with 0x30, effectively producing a monochrome display;
; ||||||| note that colour emphasis STILL works when this is on!)
; ||||||+-- Disable background clipping in leftmost 8 pixels of screen
; |||||+--- Disable sprite clipping in leftmost 8 pixels of screen
; ||||+---- Enable background rendering
; |||+----- Enable sprite rendering
; ||+------ Intensify reds (and darken other colors)
; |+------- Intensify greens (and darken other colors)
; +-------- Intensify blues (and darken other colors)
LDA #%00011110 ; enable sprites, enable background, no clipping on left side
STA $2001
;;;;;;;;;;;;;;;;;;;;
; Initialze some game state variables
InitialzeState:
LDA #$80 ; player x offset
STA playerx
LDA #$00 ; player y offset
STA playery
LDA #$C8 ; player y offset
STA ground
LDA #$00 ; controller state
STA controller1
STA playervx;
STA playervy;
STA loopCount
LDA #$03
STA gravity
Forever:
JMP Forever ;jump back to forever MAINLOOP will interrupt for game logic, infinite loop to keep the rom from exiting
;; Game main loop
MAINLOOP: ; non-maskable interrupt (draw screen)
;; Needs to be done every frame
;; Load graphics into PPU from the memory
LDA #$00 ; load 1 bytes of 0 in A
STA $2003 ; set the low byte (00) of the RAM address
LDA #$02 ; load 1 byte of $02,
STA $4014 ; set the high byte (02) of the RAM address, start the transfer
;; Draw game first
JSR Draw
;; Update game
JSR Update
RTI ; return from interrupt
;;;;;;;;;;;;;;;;;;;;;;
; Draw sprite to screen
Draw:
JSR DrawPlayer
;;This is the PPU clean up section, so rendering the next frame starts properly.
LDA #%10010000 ; enable NMI, sprites from Pattern Table 0, background from Pattern Table 1
STA $2000
LDA #%00011110 ; enable sprites, enable background, no clipping on left side
STA $2001
LDA #$00 ;;tell the ppu there is no background scrolling
STA $2005
STA $2005
RTS
;;;;;;;;;;;;;;;;;;;;;
; Draw Sprites
DrawPlayer:
LDX #$00 ; start at 0
LDY #$00 ; start at 0
DrawPlayerLoop:
LDA $0203, x ; load current x sprite position
CLC
LDA playerspriteoffset, y ; add player x with sprite offset
ADC playerx
INY ; increment sprite offset coutner
STA $0203, x ; store into RAM address ($0203 + x)
LDA $0200, x ; load current y sprite position
CLC
LDA playerspriteoffset, y ; add player y with sprite offset
ADC playery
INY
STA $0200, x ; store into RAM address ($0200 + x)
INX ; X = X + 4 loop to the next sprite
INX
INX
INX
CPX #$1C ; Compare X to hex $1C, decimal 28 meaning all 7 Player sprites done
BNE DrawPlayerLoop ; Branch to LoadSpritesLoop if compare was Not Equal to zero
; if compare was equal to 32, keep going down
RTS
DrawEnemey:
LDX #$00 ; start at 0
LDY #$00 ; start at 0
DrawEnemyLoop:
LDA $0203, x ; load current x sprite position
CLC
LDA enemyspriteoffset, y ; add player x with sprite offset
ADC enemyx
INY ; increment sprite offset coutner
STA $0203, x ; store into RAM address ($0203 + x)
LDA $0200, x ; load current y sprite position
CLC
LDA playerspriteoffset, y ; add player y with sprite offset
ADC enemyy
INY
STA $0200, x ; store into RAM address ($0200 + x)
INX ; X = X + 4 loop to the next sprite
INX
INX
INX
CPX #$08 ; Compare X to hex $1C, decimal 28 meaning all 7 Player sprites done
BNE DrawEnemyLoop ; Branch to LoadSpritesLoop if compare was Not Equal to zero
; if compare was equal to 32, keep going down
RTS
Update:
JSR LatchController
JSR PollController
JSR ReadLeft
JSR ReadRight
JSR ReadA
INC loopCount
JSR UpdatePlayerPosition
RTS
UpdatePlayerPosition:
CLC
LDA loopCount
CMP #$0A
BNE SkipGravity
LDA gravity
ADC playervy
STA playervy
LDA #$00
STA loopCount
SkipGravity:
LDA playervy
CLC
ADC playery
STA playery
CMP ground
BCS PutPlayerOnGround
PlayerOnGroundDone:
LDA playervx
CLC
ADC playerx
STA playerx
RTS
PutPlayerOnGround:
LDA ground
STA playery
LDA #$00
STA playervy
STA inAir
JMP PlayerOnGroundDone
LatchController:
LDA #$01
STA $4016
LDA #$00
STA $4016 ; tell both the controllers to latch buttons
RTS
;;;;;;;;;;;;;;;;;;
; Read controller input into byte vector
; 76543210
; ||||||||
; |||||||+- RIGHT button
; ||||||+-- LEFT Button
; |||||+--- DOWN Button
; ||||+---- UP Button
; |||+----- START Button
; ||+------ SELECT Button
; |+------- B Button
; +-------- A Button
PollController:
LDX #$00 ; 8 buttons total
PollControllerLoop:
LDA $4016 ; player 1 - A
LSR A ; shift right
ROL controller1 ; rotate left button vector in mem location $0003
INX
CPX #$08
BNE PollControllerLoop
RTS
ReadRight:
LDA controller1 ; controller1 1 - A button
AND #%00000001 ; only look at bit 0
BEQ ReadRightDone ; branch to ReadADone if button is NOT pressed (0)
; add instructions here to do something when button IS pressed (1)
LDA $0203 ; load sprite X position
CLC ; make sure the carry flag is clear
LDA playerx
ADC #$02
STA playerx;
ReadRightDone: ; handling this button is done
RTS
ReadLeft:
LDA controller1 ; controller1 1 - B button
AND #%00000010 ; only look at bit 0
BEQ ReadLeftDone ; branch to ReadBDone if button is NOT pressed (0)
; add instructions here to do something when button IS pressed (1)
LDA $0203 ; load sprite X position
CLC
LDA playerx
ADC #$FE
STA playerx
ReadLeftDone: ; handling this button is done
RTS
ReadA:
LDA controller1 ; controller1 1 - B button
AND #%10000000 ; only look at bit 0
BEQ ReadADone ; branch to ReadBDone if button is NOT pressed (0)
; add instructions here to do something when button IS pressed (1)
LDA inAir
CMP #$01
BEQ ReadADone
LDA ground
STA playery
LDA #$FA
STA playervy
LDA #$01
STA inAir
ReadADone: ; handling this button is done
RTS
;;;;;;;;;;;;;;
; Data initialization
; .db command is a macro for storing bytes in memory without having to write
; LDA (byte)
; STA (mem)
.bank 1
.org $E000
palette:
;; Background Palletes (0-3)
.db $08,$1A,$38,$18, $08,$02,$38,$3C, $08,$1C,$15,$14, $08,$02,$38,$2A
;; Character Palletes (0-3)
.db $21,$2C,$11,$15, $0F,$35,$36,$37, $0F,$39,$3A,$3B, $0F,$3D,$3E,$0F
playersprite:
; 1st byte encodes the y position
; 2nd byte encodes the tile index loaded into the PPU
; 3rd byte encodes any sprite attributes
; 76543210
; ||| ||
; ||| ++- Color Palette of sprite. Choose which set of 4 from the 16 colors to use
; |||
; ||+------ Priority (0: in front of background; 1: behind background)
; |+------- Flip sprite horizontally
; +-------- Flip sprite vertically
; 4th byte encodes the x position
;vert tile attr horiz
.db $80, $00, $00, $80 ;sprite 0
.db $80, $01, $00, $88 ;sprite 1
.db $80, $02, $00, $90 ;sprite 2
.db $88, $10, $00, $80 ;sprite 3
.db $88, $11, $00, $88 ;sprite 4
.db $88, $12, $00, $90 ;sprite 5
.db $90, $21, $00, $88 ;sprite 6
playerspriteoffset:
;x y
.db $F8, $F0; (-8, -16)
.db $00, $F0; (0, -16)
.db $08, $F0; (8 , -16)
.db $F8, $F8; (-8, -8)
.db $00, $F8; (0, -8)
.db $08, $F8; (8, -8)
.db $00, $00; (0, 0)
enemyspriteframe1:
.db $F0, $04, $00, $00
.db $F0, $05, $00, $08
enemyspriteframe2:
.db $F0, $14, $00, $00
.db $F0, $15, $00, $08
enemyspriteoffset:
.db $00, $00
.db $00, $08
background:
; nametable 960 bytes long for the background
;.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10
;.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10
;.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10
;.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10
;.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10
;.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10
;.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10
;.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;row 1
.db $11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11,$11 ;;all sky
.db $00,$01,$00,$01,$00,$01,$00,$01,$00,$01,$00,$01,$00,$01,$00,$01
.db $00,$01,$00,$01,$00,$01,$00,$01,$00,$01,$00,$01,$00,$01,$00,$01 ;;ground
.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10
.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10 ;; dirt
.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10
.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10 ;; dirt
.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10
.db $10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10,$10 ;; dirt
attribute:
; 64 bytes following a nametable
;.db $C7,$00,$00,$00, $00,$00,$00,$00
.db $00,$00,$00,$00, $00,$00,$00,$00
.db $00,$00,$00,$00, $00,$00,$00,$00
.db $00,$00,$00,$00, $00,$00,$00,$00
.db $00,$00,$00,$00, $00,$00,$00,$00
.db $00,$00,$00,$00, $00,$00,$00,$00
.db $00,$00,$00,$00, $00,$00,$00,$00
.db $00,$00,$00,$00, $00,$00,$00,$00
.db $00,$00,$00,$00, $00,$00,$00,$00
; Load in level columns
; The first 32 bytes is the first column and so on, each byte is sprite index
;columnData:
;.incbin "level.bin"
; Load column sprite attributes
; TODO how is this defined?
;attribData:
;.incbin "attr.bin"
;;;;;;;;;;;;;;
; Define interrupt vectors at the top of memory $FFFF
; Basically registering callbacks for different functions NMI, RESET, IRQ
; .org means starting at $FFFA
; .dw means store dataword, in the NES that means 16 bits 2 bytes
; stores in little endian order, superior ordering ;) least sig byte first
.bank 1
.org $FFFA ;first of the three vectors starts here
nescallback:
; after this $FFFA + 2 = $FFFC
.dw MAINLOOP ;when an NMI happens (once per frame if enabled) the
;processor will jump to the label NMI:
; after this $FFFC + 2 = $FFFE
.dw RESET ;when the processor first turns on or is reset, it will jump
;to the label RESET:
; after this $FFFC + 1 = $FFFF
.dw 0 ;external interrupt IRQ is not used in this tutorial
;;;;;;;;;;;;;;
; Load in external sprite or audio data
.bank 2
.org $0000
.incbin "art.chr" ;includes 8KB graphics file