2019-10-20 15:05:00 +00:00
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;license:MIT
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2021-12-14 19:20:16 +00:00
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;(c) 2017-2021 by qkumba/4am/John Brooks
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2019-10-20 15:05:00 +00:00
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!cpu 6502
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2021-10-16 01:34:39 +00:00
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!to "build/FX.INDEXED/PALETTE.FIZZLE",plain
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2019-10-20 15:05:00 +00:00
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*=$6000
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2021-12-14 19:20:16 +00:00
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!source "src/fx/macros.a" ; no code in here
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2019-10-20 18:13:32 +00:00
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2021-12-14 19:20:16 +00:00
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ldx #(end-start+1) ; copy LFSR code to zero page
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- ldy start-2, x
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sty $FE, x
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2019-10-20 15:05:00 +00:00
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dex
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2021-12-14 19:20:16 +00:00
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bne -
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bit <exit
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jmp loop
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start
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!pseudopc 0 {
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;X=0
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;Y=0
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loop txa
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loop1 eor #$1B ; LFSR form 0x1B00 with period 8191
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wait dex
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bpl wait
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tax
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loop2 txa
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2019-10-20 15:05:00 +00:00
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ora #$20
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2021-12-14 19:20:16 +00:00
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sta <dst+2
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2019-10-20 15:05:00 +00:00
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eor #$60
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2021-12-14 19:20:16 +00:00
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sta <src+2
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tya
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2019-10-20 15:05:00 +00:00
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ror
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2021-12-14 19:20:16 +00:00
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bcs odd
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even lda #%11010101 ; SMC
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bne + ; always branches
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odd lda #%10101010 ; SMC
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+ sta <mask+1
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src and $FD00, y ; SMC high byte
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eor (dst+1), y
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mask and #$FD ; SMC
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eor (dst+1), y
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dst sta $FD00, y ; SMC high byte
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txa
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lsr
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tax
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tya
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ror
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tay
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bcc loop2
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bne loop
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lda $C000
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bmi exit
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txa
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bne loop1
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bvc llb
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lda #%11111111
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sta <even+1
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sta <odd+1
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clv
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bvc loop ; always branches
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llb lda (src+1), y ; last lousy byte
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sta (dst+1), y
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exit rts
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}
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end
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