8255

Programmable Peripheral Interface

Pinout

DIP40
         +---\/---+
     Vss | 1    40| *RES
     RDY | 2    39| out
     out | 3    38| S0
     IRQ | 4    37| in
      NC | 5    36| NC
     NMI | 6    35| NC
     YNC | 7    34| R
     Vcc | 8    33| D0
      A0 | 9    32| D1
      A1 |10    31| D2
      A2 |11    30| D3
      A3 |12    29| D4
      A4 |13    28| D5
      A5 |14    27| D6
      A6 |15    26| D7
      A7 |16    25| A15
      A8 |17    24| A14
      A9 |18    23| A13
     A10 |19    22| A12
     A11 |20    21| Vss
         +--------+

Frequency

Set reader to FREQ, put black probe to GND, red probe to 15 to measure CPU clock

Files

• 

  Intel D8255A Datasheet

• 

  DCD D8255 Datasheet