reset.asm

reset:  ; the reset subroutine

RESET:
  SEI           ;disable IRQ
  CLD           ;disable decimal mode
  LDX #$40
  STX $4017 ;disable APU frame IRQ
  LDX #$FF
  TXS           ;set up the stack
  INX           ;now x = 0 (wrapped back around) so we don't need to STX for clrmem
  STX $2000 ;disable NMI
  STX $2001 ;disable rendering
  STX $4010 ;disable DMC IRQs

  JSR vblankwait

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
  INX
  BNE clrmem

  JSR vblankwait

LoadPalettes:
  LDA $2002
  LDA #$3F
  STA $2006
  LDA #$00
  STA $2006
  LDX #$00

LoadPalettesLoop:
  LDA palette, X
  STA $2007
  INX
  CPX #$20
  BNE LoadPalettesLoop

LoadSprites:
  LDX #$00

LoadSpritesLoop:
  LDA sprites, X
  STA $0200, X
  INX
  CPX #$10
  BNE LoadSpritesLoop

LoadBackground:
  LDA $2002
  LDA #$20
  STA $2006
  LDA #$00
  STA $2006
  LDX #$00
  LDY #$00

LoadBackgroundLoop:
  LDA background, x
  STA $2007
  INX
  CPX #$80
  BNE LoadBackgroundLoop
  INY
  LDX #$00
  CPY #$08
  BNE LoadBackgroundLoop

LoadAttribute:
  LDA $2002
  LDA #$23
  STA $2006
  LDA #$C0
  STA $2006
  LDX #$80
  LDA #$00

LoadAttributeLoop:
  STA $2007
  DEX
  BNE LoadAttributeLoop

PlayerVariablesInit:
  ;; Let's set some initial stats here
  ;object speed
  LDA #$01

  STA speedx

  ;player speed
  LDA #$02
  STA speedy

  ; initial score

  LDA #$00
  STA score

  ; set collide flag to off
  STA collide_flag

  ; player position
  LDA #$80
  STA player

  LDA #$10
  STA player ; static

  ;; Set starting game state

  LDA #STATEPLAYING
  STA gamestate

  LDA #$00
  STA scroll
  sta nametable

  sta sleep_flag
  sta draw_flag
  jsr sound_engine_init ; initialize the sound engine

PPU_Init:

  ;; Finish up our initialization -- begin rendering graphics and enable sound

  LDA #%10010000   ; enable NMI, sprites from Pattern Table 1
  STA $2000
  LDA #%00010000
  STA $2001

  rts