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.MEMORYMAP
SLOTSIZE $2000
DEFAULTSLOT 0
SLOT 0 $C000
SLOT 1 $E000
.ENDME
.ROMBANKMAP
BANKSTOTAL 2
BANKSIZE $2000
BANKS 2
.ENDRO
.bank 0
.org $0000
RESET:
SEI ; disable IRQs
CLD ; disable decimal mode
LDX #$40
STX $4017.W ; disable APU frame IRQ
LDX #$FF
TXS ; Set up stack
INX ; now X = 0
STX $2000.W ; disable NMI
STX $2001.W ; disable rendering
STX $4010.W ; disable DMC IRQs
vblankwait1: ; First wait for vblank to make sure PPU is ready
BIT $2002
BPL vblankwait1
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
vblankwait2: ; Second wait for vblank, PPU is ready after this
BIT $2002
BPL vblankwait2
LDA #%10000000 ;intensify blues
STA $2001
LDX #$00
read_controller1:
; latch
LDA #$01
STA $4016
LDA #$00
STA $4016
; clock
LDA $4016 ; A
AND #%00000001
TAY
LDA $4016 ; B
LDA $4016 ; Select
LDA $4016 ; Start
LDA $4016 ; Up
LDA $4016 ; Down
LDA $4016 ; Left
LDA $4016 ; Right
CPY #$00
BEQ read_controller1
CPX #$00
BEQ turn_green
CPX #$01
BEQ turn_red
turn_blue:
LDA #%10000000
STA $2001
LDX #$00
JMP read_controller1
turn_green:
LDA #%01000000
STA $2001
LDX #$01
JMP read_controller1
turn_red:
LDA #%00100000
STA $2001
LDX #$02
JMP read_controller1
NMI:
RTI
.bank 1 slot 1
.orga $FFFA ;first of the three vectors starts here
.dw NMI ;when an NMI happens (once per frame if enabled) the
;processor will jump to the label NMI:
.dw RESET ;when the processor first turns on or is reset, it will jump
;to the label RESET:
.dw 0 ;external interrupt IRQ is not used in this tutorial
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