mirror of
https://github.com/sehugg/8bitworkshop.git
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49 lines
949 B
NASM
49 lines
949 B
NASM
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include "nesdefs.asm"
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;;;;; VARIABLES
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seg.u RAM
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org $0
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;;;;; NES CARTRIDGE HEADER
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NES_HEADER 0,2,1,0 ; mapper 0, 2 PRGs, 1 CHR, horiz. mirror
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;;;;; START OF CODE
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Start:
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; wait for PPU warmup; clear CPU RAM
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NES_INIT ; set up stack pointer, turn off PPU
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jsr WaitSync ; wait for VSYNC
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jsr ClearRAM ; clear RAM
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jsr WaitSync ; wait for VSYNC (and PPU warmup)
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; set palette
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lda #$3f ; $3F -> A register
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sta PPU_ADDR ; write high byte first
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lda #$00 ; $00 -> A register
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sta PPU_ADDR ; $3F00 -> PPU address
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lda #$1c ; $1C = light blue color
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sta PPU_DATA ; $1C -> PPU data
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; activate PPU graphics
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lda #MASK_COLOR
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sta PPU_MASK ; enable rendering
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lda #CTRL_NMI
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sta PPU_CTRL ; enable NMI
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.endless
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jmp .endless ; endless loop
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;;;;; COMMON SUBROUTINES
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include "nesppu.asm"
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;;;;; INTERRUPT HANDLERS
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NMIHandler:
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rti
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;;;;; CPU VECTORS
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NES_VECTORS
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