73 lines
2.9 KiB
NASM
73 lines
2.9 KiB
NASM
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!DISP_REG = $2100 ; Screen Display Register
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!VMAIN_REG = $2115 ; Video Port Control Register
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!VRAM_LOW_REG = $2116 ; VRAM Address Registers (Low)
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!VRAM_HIGH_REG = $2117 ; VRAM Address Registers (High)
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!VRAM_WRITE_REG = #$18 ; VRAM Data Write Registers (Low) (you always store it to the dest register so no need for the actual address)
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!DMA0_REG = $4300 ; DMA Control Register - channel 0
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!DMA0_DEST_REG = $4301 ; DMA Destination Register
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!DMA0_SRC_LOW_REG = $4302 ; DMA Source Address Register (Low)
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!DMA0_SRC_HIGH_REG = $4303 ; DMA Source Address Register (High)
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!DMA0_SRC_BANK_REG = $4304 ; DMA Source Address Register (Bank)
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!DMA0_SIZE_LOW_REG = $4305 ; DMA Size Registers (Low)
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!DMA0_SIZE_HIGH_REG = $4306 ; DMA Size Registers (Low)
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!DMA_ENABLE_REG = $420B ; DMA Enable Register
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macro DMA_VRAM(VRAM_HIGH,VRAM_LOW,SRC_BANK,SRC_HIGH,SRC_LOW,LENGTH_HIGH,LENGTH_LOW)
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PHA
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; --- preserve DMA registers ----------------------------------------------------
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LDA !DMA0_REG : PHA
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LDA !DMA0_DEST_REG : PHA
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LDA !DMA0_SRC_LOW_REG : PHA
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LDA !DMA0_SRC_HIGH_REG : PHA
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LDA !DMA0_SRC_BANK_REG : PHA
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LDA !DMA0_SIZE_LOW_REG : PHA
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LDA !DMA0_SIZE_HIGH_REG : PHA
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; -------------------------------------------------------------------------------
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;LDA.b #$80 : STA !DISP_REG ; force vblank
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LDA #$80 : STA !VMAIN_REG
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; write to vram at $<VRAM_HIGH><VRAM_LOW>
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LDA <VRAM_LOW> : STA !VRAM_LOW_REG ; Set VRAM destination address low byte
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LDA <VRAM_HIGH> : STA !VRAM_HIGH_REG ; Set VRAM destination address high byte
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; Set DMA0 to write a word at a time.
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LDA #$01
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STA !DMA0_REG
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; Write to $2118 & $2119 - VRAM Data Write Registers (Low) & VRAM Data Write Registers (High)
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; setting word write mode on DMA0_REG causes a write to $2118 and then $2119
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; $21xx is assumed
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LDA #$18
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STA !DMA0_DEST_REG
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; Read from $<SRC_BANK>:<SRC_HIGH><SRC_LOW>.
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LDA.b <SRC_LOW>
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STA !DMA0_SRC_LOW_REG ; set src address low byte
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LDA.b <SRC_HIGH>
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STA !DMA0_SRC_HIGH_REG ; set src address high byte
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LDA.b <SRC_BANK>
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STA !DMA0_SRC_BANK_REG ; set src address bank byte
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; total bytes to copy: #$1000 bytes.
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LDA <LENGTH_LOW> : STA $4305 ; length low byte
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LDA <LENGTH_HIGH> : STA $4306 ; length high byte
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; start DMA on channel 0
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LDA #$01 ; channel select bitmask
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STA !DMA_ENABLE_REG
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; --- restore DMA registers -----------------------------------------------------
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PLA : STA !DMA0_SIZE_HIGH_REG
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PLA : STA !DMA0_SIZE_LOW_REG
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PLA : STA !DMA0_SRC_BANK_REG
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PLA : STA !DMA0_SRC_HIGH_REG
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PLA : STA !DMA0_SRC_LOW_REG
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PLA : STA !DMA0_DEST_REG
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PLA : STA !DMA0_REG
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; -------------------------------------------------------------------------------
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PLA
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endmacro
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