Using Pfi Terminals As Static Digital I/Os; Using Pfi Terminals To Digital Detection Events; Connecting Pfi Input Signals - National Instruments DAQ X Series User Manual

Chapter 8 PFI

Using PFI Terminals as Static Digital I/Os

Each PFI can be individually configured as a static digital input or a static
digital output. When a terminal is used as a static digital input or output,
it is called P1.x or P2.x. On the I/O connector, each terminal is labeled
PFI x/P1.x or PFI x/P2.x.
In addition, X Series devices have up to 32 lines of bidirectional DIO
signals.

Using PFI Terminals to Digital Detection Events

Each PFI can be configured to detect digital changes. The values on the PFI
lines cannot be read in a hardware-timed task, but they can be used to fire
the change detection event. For example, if you wanted to do change
detection on eight timed DIO lines but wanted to ensure that the value of
the lines was updated every second independent of the eight lines changing
you could set a PFI line up for change detection and connect a 1 Hz signal
to it.

Connecting PFI Input Signals

All PFI input connections are referenced to D GND. Figure 8-2 shows this
reference, and how to connect an external PFI 0 source and an external
PFI 2 source to two PFI terminals.
X Series User Manual
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