Di Change Detection - National Instruments DAQ X Series User Manual

Chapter 6 Digital I/O

DI Change Detection

You can configure the DAQ device to detect changes on all 32 digital input
lines (P0, P1, and P2) and all 16 PFI lines. Figure 6-11 shows a block
diagram of the DIO change detection circuitry.
P0.0
Synch
P2.7
Synch
You can enable the DIO change detection circuitry to detect rising edges,
falling edges, or either edge individually on each DIO line. The DAQ
devices synchronize each DI signal to the 100 MHz Timebase, and then
sends the signal to the change detectors. The circuitry ORs the output of all
enabled change detectors from every DI signal. The result of this OR is the
Change Detection Event signal.
Change detection performs bus correlation by considering all changes
within a 50 ns window one change detection event. This keeps signals on
the same bus synchronized in samples and prevents overruns.
X Series User Manual
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Figure 6-11. DI Change Detection
6-24
Change Detection Event
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