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Chapter 4 Analog Input
NI 6124/6154 User Manual 4-18 ni.com
AI Hold Complete Event Signal
The AI Hold Complete Event (ai/HoldCompleteEvent) signal
generates a pulse after each A/D conversion begins. You can route
ai/HoldCompleteEvent out to any PFI <0..15> or RTSI <0..7> terminal.
The polarity of ai/HoldCompleteEvent is software-selectable, but is
typically configured so that a low-to-high leading edge can clock external
AI multiplexers indicating when the input signal has been sampled and can
be removed.
AI Start Trigger Signal
Use the AI Start Trigger (ai/StartTrigger) 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:
• When a certain number of points are 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.
Using a Digital Source
To use AI Start Trigger with a digital source, specify a source and an edge.
The source can be any of the following signals:
• PFI <0..15>
•RTSI <0..7>
• Counter n Internal Output
•PXI_STAR
The source also can 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 in version 8.0 or later for more information.
You also can specify whether the measurement acquisition begins on the
rising edge or falling edge of AI Start Trigger.