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15% faster SHR fizzle fade

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This commit is contained in:
4am 2020-09-03 18:42:38 -04:00
parent 6ae0509874
commit 5a90ba8555
2 changed files with 27 additions and 28 deletions
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2
src/fx/fx.hgr.1bit.fizzle.a
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@ -1,5 +1,5 @@
;license:MIT
;(c) 2017-2019 by qkumba
;(c) 2017-2020 by qkumba/4am
!cpu 6502
!to "build/FX/BIT.FIZZLE",plain

53
src/fx/fx.shr.fizzle.a
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@ -1,16 +1,19 @@
;license:MIT
;(c) 2019 by qkumba
;(c) 2019-2020 by qkumba/4am
!cpu 6502
!to "build/FX/SHR.FIZZLE",plain
*=$a000
rnd1=$fe
rnd2=$ff
;init RNG
ldy #1
sty @rnd1+1
sty rnd1
dey
sty @rnd2+1
sty rnd2
;copy SCB and palette
@ -37,59 +40,55 @@
;iterate
@loop
ldy @rnd1+1
ldx @rnd2+1
lsr @rnd2+1
ror @rnd1+1
ldx rnd1
@loop2
stx $26
stx $3c
ldx rnd2
lsr rnd2
ror rnd1
bcc +
;feedback polynomial forms #$4001 for period of 32767
lda @rnd1+1
lda rnd1
eor #1
sta @rnd1+1
lda @rnd2+1
sta rnd1
lda rnd2
eor #$40
sta @rnd2+1
sta rnd2
;don't rewrite SCB or palette
;it will make the fizzle take longer than obviously needed
+ cpx #$7d
bcs +
sty $26
sty $3c
txa
;select address
;clc
adc #$20
sta $27
sta $3d
;copy pixel from other page to this page
ldy #0
lda ($3c),y
sta $c005
sta ($26),y
sta $c004
;wait while checking for keypress
+
;exit conditions
+ ;ldx #2
@wait lda $c000
ldx rnd2
bne @loop
ldx $c000
bmi @exit
;dex
;bne @wait
;and exit condition
@rnd2 lda #0
bne @loop
@rnd1 lda #0
cmp #1
bne @loop
ldx rnd1
cpx #1
bne @loop2
@exit rts