silverdr_at_inet.com.pl
Date: 2005-10-02 23:26:21
Hello floppy experts. I am looking for an explanation to the 1541
code snippet below.
[... entering with X=0]
TXA ; LDA #$00
LDY #$A2 ; 162 times? 324 GCR bytes probably...
L75F:
BVC *
CLV
EOR $1801 ; get the byte from parallel port
STA $1C01 ; write to disk
DEC $1800 ; acknowledge (DATA HI?)
LDA $1801
BVC *
CLV
EOR $1801 ; zero out??!
STA $1C01
INC $1800 ; acknowledge (DATA LO?)
LDA $1801
DEY
BNE L75F
I am not sure if I am missing something very obvious but I just don't
understand WTH is the EOR $1801 for and how come does
LDA $xxxx
EOR $xxxx
not zero the A?? Please someone enlighten me on that...
--
If your law requires a police state to enforce, your law is wrong.
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