drive-side routine

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Date: 2005-10-02 23:26:21

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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...

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