CIA-A Address BFEx01  data bits 7-0  (A12*) (int2)
--------------------------------------------------

   PA7..game port 1, pin 6 (fire button*)
   PA6..game port 0, pin 6 (fire button*)
   PA5.. rdy*      disk ready*
   PA4.. tk0*      disk track 00*
   PA3.. wpro*     write protect*
   PA2.. chng*     disk change*
   PA1..LED*       led light (0=bright)/audio filter control (A500 & A2000)
   PA0..OVL        ROM/RAM overlay bit

   SP... kdat      keyboard data
   CNT.. kclk      keyboard clock
   PB7..P7         data 7
   PB6..P6         data 6
   PB5..P5         data 5     Centronics parallel interface
   PB4..P4         data 4          data
   PB3..P3         data 3
   PB2..P2         data 2
   PB1..P1         data 1
   PB0..P0  data 0

   PC... drdy*                centronics control
   F.... ack* 


CIA-B Address BFDx00  data bits 15-8   (A13*) (int6)
-----------------------------------------------------

   PA7..com line  dtr* , driven output
   PA6..com line  rts* , driven output
   PA5..com line carrier detect*
   PA4..com line  cts* 
   PA3..com line  dsr* 
   PA2.. sel       centronics control
   PA1.. pout +--- paper out ------------+
   PA0.. busy | +--busy    -------------+ |
              | |                       | |
   SP... busy | +- commodore serial bus + |
   CNT.. pout +----commodore serial bus --+

   PB7.. mtr*      motor
   PB6.. sel3*     select external 3rd drive
   PB5.. sel2*     select external 2nd drive
   PB4.. sel1*     select external 1st drive
   PB3.. sel0*     select internal drive
   PB2.. side*     side select*
   PB1.. dir       direction
   PB0.. step*     step*

   PC...not used
   F.... index*    disk index pulse*