$1C01/7169/VIA2+1:   Data Port A (Data to/from head)

ROM-Reference:

 EOR $1C01  : $F6AB $F6B8
 LDA $1C01  : $F3C1 $F3CB $F4D7 $F4E4 $F540 $F567 $FD43 $FD6A $FD7A
 STA $1C01  : $F5A7 $F5B9 $F5C4 $FB14 $FCB3 $FCC8 $FCD6 $FCE3 $FCF1 $FCFE
              $FD0C $FDB2 $FE1F