National Instruments DAQ X Series User Manual

Chapter 4 Analog Input
© National Instruments 4-59 X Series User Manual
Routing AI Start Trigger to an Output Terminal
You can route AI 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 AI Start Trigger to initiate pretriggered DAQ
operations. In most pretriggered applications, a software trigger generates
AI Start Trigger. Refer to the AI Reference Trigger Signal section for a
complete description of the use of AI Start Trigger and AI Reference
Trigger in a pretriggered DAQ operation.
AI Reference Trigger Signal
Use AI Reference Trigger (ai/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.
Note (NI USB-6356/6366 Devices) Yo u can select the buffer on the host or on the
NI USB-6356/6366 device. To enable a Reference Trigger to Onboard Memory, set the
AI Data Transfer Request Condition property in NI-DAQmx to When Acquisition
Complete.
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 KnowledgeBase document, Can a Pretriggered Acquisition be
Continuous?, for more information. To access this KnowledgeBase, go to
ni.com/info and enter the Info Code rdcanq.
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National Instruments DAQ X Series Specifications

General

Brand	National Instruments
Model	DAQ X Series
Category	I/O Systems
Language	English