ADLINK DAQe-2502 - Manual (Page 55)

Operation Theory 45
4.3 General Purpose Digital I/O
The DAQ-/DAQe-/PXI-2502/2501 card provides a 24-line general-
purpose digital I/O (GPIO) via the 82C55A chip.
The 24-line GPIO are separated into three ports: Port A, Port B
and Port C. High nibble (bit[7…4]), and low nibble (bit[3…0]) of
each port can be individually programmed to be either inputs or
outputs. Upon system startup or reset, all GPIO pins are reset to
high impedance inputs.
For more information on 82C55A programmable I/O chip, visit
http://www.intel.com.