Operation Theory
39
Figure 4-16: Stop mode III
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.