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Improved SHRCOORD conversion (Y-axis)

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Bobbi Webber-Manners 2022-12-29 23:39:04 -05:00
parent 552e29dd29
commit ae7c263fed
2 changed files with 19 additions and 17 deletions
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applecorn.po
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mainmem.shr.s
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@ -272,28 +272,30 @@ SHRCOORD PHP ; Disable interrupts
BRA :Y
:MODE0 LDA SHRVDUQ+5
LSR ; /2
STA A1L ; Resulr in A1L/H
STA A1L ; Result in A1L/H
* Y-coordinate in SHRVDUQ+7,+8 1024*3/16=192, 1024/128=8, 192+8=200
* Y-coordinate in SHRVDUQ+7,+8 1024*25/128=200
:Y LDA SHRVDUQ+7
ASL ; *2
CLC
ADC SHRVDUQ+7 ; *3
LSR ; *3/2
LSR ; *3/4
LSR ; *3/8
LSR ; *3/16
STA A2L ; (A1L and A1H)
ASL ; *4
ASL ; *8
ASL ; *16
STA A2L ; (A2L and A2H)
LDA SHRVDUQ+7
LSR ; /2
LSR ; /4
LSR ; /8
LSR ; /16
LSR ; /32
LSR ; /64
LSR ; /128
ASL ; *2
ASL ; *4
ASL ; *8
CLC
ADC A2L ; Result
ADC A2L ; *16 + *8 -> *24
; CLC ; We know it is clear
ADC SHRVDUQ+7 ; *25
LSR ; *25/2
LSR ; *25/4
LSR ; *25/8
LSR ; *25/16
LSR ; *25/32
LSR ; *25/64
LSR ; *25/128
STA A2L ; Into A2L/H
SEC ; Back to emulation mode