mirror of https://github.com/a2-4am/4cade.git
58 lines
1.1 KiB
Plaintext
58 lines
1.1 KiB
Plaintext
;license:MIT
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;(c) 2017-2021 by qkumba/4am/John Brooks
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!cpu 6502
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!to "build/GR.FIZZLE",plain
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*=$6000
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!source "src/fx/macros.a"
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+OVERCOPY_TO_0 start, end
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;$FF clobbered
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;X=0
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;Y=0
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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 #$05 ; LFSR form 0x0500 with period 2047
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wait inx
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bpl wait
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tax
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loop2 txa
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and #$03
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ora #$04
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sta <dst+2
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eor #$44
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sta <src+2
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lda #%00001111
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cpx #$04
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bcc +
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lda #%11110000
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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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bit $C000
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bmi exit
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txa
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bne loop1
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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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