Using An Internal Source; Using An External Source; Routing Di Sample Clock To An Output Terminal; Other Timing Requirements - National Instruments DAQ X NI 634 Series User Manual

If the DAQ device receives a DI Sample Clock when the FIFO is full, it reports an overflow error
to the host software.

Using an Internal Source

To use DI Sample Clock with an internal source, specify the signal source and the polarity of the
signal. The source can be any of the following signals:
• DI Sample Clock (di/SampleClock)
• DO Sample Clock (do/SampleClock)
• AI Sample Clock (ai/SampleClock)
• AI Convert Clock (ai/ConvertClock)
• AO Sample Clock (ao/SampleClock)
• Counter n Sample Clock
• Counter n Internal Output
• Frequency Output
• DI Change Detection output
Several other internal signals can be routed to DI Sample Clock through internal routes. Refer
to Device Routing in MAX in the NI-DAQmx Help or the LabVIEW Help for more information.

Using an External Source

You can route any of the following signals as DI Sample Clock:
• PFI <0..15>
• RTSI <0..7>
• PXI_STAR
• PXIe_DSTAR<A,B>
• Analog Comparison Event (an analog trigger)
You can sample data on the rising or falling edge of DI Sample Clock.

Routing DI Sample Clock to an Output Terminal

You can route DI Sample Clock out to any PFI <0..15> terminal. The PFI circuitry inverts the
polarity of DI Sample Clock before driving the PFI terminal.

Other Timing Requirements

Your DAQ device only acquires data during an acquisition. The device ignores DI Sample Clock
when a measurement acquisition is not in progress. During a measurement acquisition, you can
cause your DAQ device to ignore DI Sample Clock using the DI Pause Trigger signal.
The DI timing engine on your device internally generates DI Sample Clock unless you select an
external source. DI Start Trigger starts the timing engine and either software or hardware can
X Series User Manual
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