Using An Analog Source; Routing Di Start Trigger To An Output Terminal; Di Reference Trigger Signal - National Instruments X Series User Manual

Chapter 6 Digital I/O
• PXI_STAR
• PXIe_DSTAR<A,B>
• Change Detection Event
• AI Start Trigger (ai/StartTrigger)
• AO Start Trigger (ao/StartTrigger)
• DO Start Trigger (do/StartTrigger)
The source can also be one of several other internal signals on your DAQ device. Refer to Device
Routing in MAX in the NI-DAQmx Help or the LabVIEW Help for more information.
You can also specify whether the measurement acquisition begins on the rising edge or falling
edge of DI Start Trigger.

Using an Analog Source

When you use an analog trigger source, the acquisition begins on the first rising or falling edge
of the Analog Comparison Event signal.

Routing DI Start Trigger to an Output Terminal

You can route DI Start Trigger out to any PFI <0..15>, RTSI <0..7>, or PXIe_DSTARC
terminal. The output is an active high pulse. All PFI terminals are configured as inputs by
default.
The device also uses DI Start Trigger to initiate pretriggered DAQ operations. In most
pretriggered applications, a software trigger generates DI Start Trigger. Refer to the

DI Reference Trigger Signal

DI Reference Trigger in a pretriggered DAQ operation.
DI Reference Trigger Signal
Use the DI Reference Trigger (di/ReferenceTrigger) signal to stop a measurement acquisition.
To use a reference trigger, specify a buffer of finite size and a number of pretrigger samples
(samples that occur before the reference trigger). The number of posttrigger samples (samples
that occur after the reference trigger) desired is the buffer size minus the number of pretrigger
samples.
Once the acquisition begins, the DAQ device writes samples to the buffer. After the DAQ device
captures the specified number of pretrigger samples, the DAQ device begins to look for the
reference trigger condition. If the reference trigger condition occurs before the DAQ device
captures the specified number of pretrigger samples, the DAQ device ignores the condition.
If the buffer becomes full, the DAQ device continuously discards the oldest samples in the buffer
to make space for the next sample. This data can be accessed (with some limitations) before the
DAQ device discards it. Refer to the document, Can a Pretriggered Analog Acquisition be
Continuous?, for more information. To access this document, go to
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