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*