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More Videx code cleanup/improvement.

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Bobbi Webber-Manners 2024-08-05 17:55:17 -04:00
parent 1560720c5b
commit 2eea66deae
1 changed files with 10 additions and 20 deletions
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30
drivers/a2vt100.s
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@ -1250,39 +1250,29 @@ VidexSetVec
lsr ; ..
sta xVector+1 ; Store MSByte
pla ; Recover row * 5 + start
asl ; Mult*15 - for LSbyte
asl ; Mult*16 - for LSbyte
asl ; ..
asl ; ..
asl ; ..
sta xVector ; Store LSByte
VSV2 clc
clc
txa ; Column -> A
adc xVector
sta xVector
sta BASL
sta BASL ; Store LSByte
lda xVector+1
adc #00
sta xVector+1 ; Now xVector has start + row * 80 + col
lsr ; Discard LSbit of MSbyte
and #$03 ; Mask to get bits 9,10
tay ; Videx page 0,1,2,3
asl ; Multiply by 4
asl ; ..
adc #00 ; Now xVector has start + row * 80 + col
pha
and #$06 ; Mask to get bits 9,10
asl ; Multiply by 2
tax ; Will return page*4 in X
beq VSV4 ; Page zero -> skip over loop
VSV3 lda xVector+1 ; MSB
sec
sbc #$02 ; Subtract 2 from MSB -> sub 512 from value
pla ; Recover MSByte
and #$01 ; Mask out all except LSbit
sta xVector+1
dey
bne VSV3
VSV4 lda xVector+1
sta BASH
sta BASH ; Store MSByte
rts
VSVTmp .res 1
; -------------------------------------
; VidexPage - Page in the 512 byte page videxpage
;