ADLINK PXI-2502 - Manual (Page 44)

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• Operation Theoreym
4.3 General Purpose Digital I/O
DAQ/PXI-2500 SERIES provides 24-line general-purpose digital I/O
(GPIO) through a 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 indi-
vidually programmed to be either inputs or outputs. Upon system startup
or reset, all the GPIO pins are reset to high impedance inputs.
For more information on programmable I/O chip 82C55A, please refer to
http://www.intel.com.