49 lines
934 B
Plaintext
49 lines
934 B
Plaintext
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include "nesdefs.dasm"
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;;;;; VARIABLES
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seg.u ZEROPAGE
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org $0
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;;;;; NES CARTRIDGE HEADER
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NES_HEADER 0,2,1,NES_MIRR_HORIZ ; mapper 0, 2 PRGs, 1 CHR
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;;;;; START OF CODE
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Start: subroutine
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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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lda #$3f ; $3F -> A register
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ldy #$00 ; $00 -> Y register
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sta PPU_ADDR ; write high byte first
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sty 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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lda #CTRL_NMI
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sta PPU_CTRL ; enable NMI
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lda #MASK_COLOR
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sta PPU_MASK ; enable rendering
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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.dasm"
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;;;;; INTERRUPT HANDLERS
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NMIHandler: subroutine
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SAVE_REGS
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RESTORE_REGS
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rti
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;;;;; CPU VECTORS
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NES_VECTORS
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