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100 lines
1.6 KiB
NASM
100 lines
1.6 KiB
NASM
;------------------------------------------------------------------------------
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; This is a direct port of Michael Martin's tutorial project for NES101
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; With some modifications to the tile map, and extra comments, and ported to
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; suit my assembler. - Saf
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; See:
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; http://hackipedia.org/Platform/Nintendo/NES/tutorial,%20NES%20programming%20101/NES101.html
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;
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;;;;
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; Create an iNES header
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.ines {"prog": 1, "char": 0, "mapper": 0, "mirror": 0}
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;;;;
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; Here is a good spot to associate zero page memory addresses
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; with quick access variables in the program.
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.org $0200
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sprite:
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;;;;
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; Setup the interrupt vectors
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.org $FFFA
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.dw vblank
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.dw main
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.dw irq
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.org $C000
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;;;;
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; Here is our code entry point, which we'll call main.
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main:
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; Disable interrupts and decimal flag
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sei
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cld
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; Wait for 2 vblanks
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wait_vb1:
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lda $2002
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bpl wait_vb1
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wait_vb2:
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lda $2002
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bpl wait_vb2
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; Now we want to initialize the hardware to a known state
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lda #$00
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ldx #$00
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clear_segments:
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sta $00, X
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sta $0100, X
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sta $0200, X
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sta $0300, X
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sta $0400, X
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sta $0500, X
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sta $0600, X
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sta $0700, X
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inx
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bne clear_segments
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; Reset the stack pointer
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ldx #$FF
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txs
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; Disable all graphics.
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lda #$00
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sta $2000
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sta $2001
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; Init APU
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ldx #$0F
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stx $4015
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; Turn on noise tone
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ldx #$85
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stx $400E
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; Set volume to max
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ldx #$3F
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stx $400C
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; Load Length counter
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ldx #$01
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stx $400F
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; Resume interrupts and loop here forever
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cli
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forever:
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jmp forever
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;;;;
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; Update everything on every vblank
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vblank:
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rti
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;;;;
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; Don't do anything on IRQ
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irq:
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rti
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