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|
;;;
;; This is an empty wrapper for the NES. It does some basic hardware
;; initialization and finally calls a `Main` subroutine that is to be provided
;; by another file. After that, it loops indefinitely.
;;
;; There are some variations of this file already, I just took it from
;; NESHacker: https://github.com/NesHacker (definitely check his Youtube
;; channel, it's extra-dope!); originally licensed under the MIT License.
;;;
.import Main
.segment "HEADER"
.byte $4E, $45, $53, $1A ; iNES header identifier
.byte 2 ; 2x 16KB PRG-ROM Banks
.byte 1 ; 1x 8KB CHR-ROM
.byte $01, $00 ; mapper 0, vertical mirroring
.segment "VECTORS"
.addr nmi
.addr reset
.addr 0
.segment "STARTUP"
.segment "CHARS"
.segment "CODE"
.proc nmi
bit $2002
lda #0
sta $2006
sta $2006
rti
.endproc
.proc ResetPalettes
bit $2002
lda #$3f
sta $2006
lda #$00
sta $2006
lda #$0F
ldx #$20
@paletteLoadLoop:
sta $2007
dex
bne @paletteLoadLoop
rts
.endproc
.proc reset
sei
cld
ldx #%01000000
stx $4017
ldx #$ff
txs
ldx #0
stx $2000
stx $2001
stx $4010
bit $2002
@vblankWait1:
bit $2002
bpl @vblankWait1
@clearMemory:
lda #$00
sta $0000, x
sta $0100, x
sta $0200, x
sta $0300, x
sta $0400, x
sta $0500, x
sta $0600, x
sta $0700, x
inx
bne @clearMemory
@vblankWait2:
bit $2002
bpl @vblankWait2
jsr ResetPalettes
main:
jsr Main
lda #%00001000
sta $2001
endlessLoop:
jmp endlessLoop
.endproc
|
