User`s guide

48 • Operation Theory
(UC _Counter=4, IC_Counter=3)
4 update counts, infinite iterations
DAWR
WFG_in_progress
Operation start
Trigger
Output Waveform
0
2
4
Software stop command
Figure 30: Stop mode III
4.3 Digital I/O
DAQ/PXI-22XX contains 24-lines of general-purpose digital I/O (GPIO),
which is provided through a 82C55A chip.
The 24-lines GPIO are separated into three ports: Port A, Port B and Port C.
Port A, Port B, Port C high nibble (bit-4 to bit-7), and low nibble (bit 0 to bit
3) can be programmed to be input or output individually. At system startup
and reset, all the I/O pins are all reset to be input configuration, that is, high
impedance.
DAQ/PXI-2204 also provides 4 digital inputs (SDI from CN2), which are
sampled simultaneously with the analog signal input and stored with the
12-bit AD data. Please refer to 4.1.1.1 for the details.