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Using an External Source

You can route the following signals as DI Sample Clock:

• Any PFI terminal

• 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 to any output PFI terminal. The PFI circuitry inverts the

polarity of DI Sample Clock before driving the PFI terminal.

DI Start Trigger Signal

Use the DI Start Trigger signal to begin a measurement acquisition. A measurement

acquisition consists of one or more samples. If you do not use triggers, begin a measurement

with a software command. Once the acquisition begins, configure the acquisition to stop in one

of the following ways:

• When a certain number of points has been sampled (in finite mode)

• After a hardware reference trigger (in finite mode)

• With a software command (in continuous mode)

An acquisition that uses a start trigger (but not a reference trigger) is sometimes referred to as

a posttriggered acquisition. That is, samples are measured only after the trigger.

When you are using an internal sample clock, you can specify a delay from the start trigger to

the first sample.

Using a Time Source

To use the Start Trigger signal with a time source, configure a specific time in NI-DAQmx.

Refer to the "Timestamps" and "Time Triggering" topics in the NI-DAQmx Help for more

information on accessing time-based features in the NI-DAQmx API.

Using a Digital Source

To use DI Start Trigger with a digital source, specify a source and a rising or falling edge. Use

the following signals as the source:

• Any PFI terminal

• Counter n Internal Output

The source also can be one of several other internal signals on the cRIO controller. Refer to the

"Device Routing in MAX" topic in the NI-DAQmx Help or the LabVIEW Help for more

information.

Routing DI Start Trigger to an Output Terminal

You can route DI Start Trigger to any output PFI terminal. The output is an active high pulse.

National Instruments cRIO-904 Series User Manual

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