mirror of https://github.com/a2-4am/4cade.git
109 lines
1.8 KiB
Plaintext
109 lines
1.8 KiB
Plaintext
;license:MIT
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;(c) 2019 by 4am
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;
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!cpu 6502
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!to "build/FX.INDEXED/R.BY.2",plain
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*=$6000
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maskindex = $fd
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row = $fe
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col = $ff
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!source "src/fx/macros.a"
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!source "src/constants.a"
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lda #0
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sta col
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ColLoop
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lda #0
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sta row
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jsr WaitForVBL
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RowLoop
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lda row
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+HGR_ROW_CALC
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lda col
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ror
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bcs OddCol
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ldx #7
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ldy col
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- lda ($26),y
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eor ($3c),y
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and copymask_even
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eor ($26),y
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sta ($26),y
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clc
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+HGR_INC_WITHIN_BLOCK
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dex
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bpl -
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bmi NextRow ; always branches
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OddCol
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ldx #7
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ldy col
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- lda ($26),y
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eor ($3c),y
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and copymask_odd
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eor ($26),y
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sta ($26),y
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clc
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+HGR_INC_WITHIN_BLOCK
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dex
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bpl -
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NextRow
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inc row
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lda row
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cmp #24
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+LBNE RowLoop
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lda $c000
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bmi Exit
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inc col
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lda col
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cmp #40
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+LBNE ColLoop
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beq Phase2
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Exit jmp UnwaitForVBL
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Phase2
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lda #0
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sta col
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ColLoop2
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lda #0
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sta row
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jsr WaitForVBL
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RowLoop2
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lda row
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+HGR_ROW_CALC
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ldx #7
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ldy col
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- lda ($3c),y
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sta ($26),y
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clc
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+HGR_INC_WITHIN_BLOCK
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dex
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bpl -
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inc row
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lda row
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cmp #24
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+LBNE RowLoop2
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lda $c000
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bmi Exit2
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inc col
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lda col
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cmp #40
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+LBNE ColLoop2
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Exit2 jmp UnwaitForVBL
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copymask_even
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!byte %11001100
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copymask_odd
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!byte %10110011
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!source "src/wait.a"
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