Chapter 4 Analog Input
© National Instruments 4-57 X Series User Manual
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 Hold
Complete Event out to any PFI <0..15>, RTSI <0..7>, or PXIe-DSTARC
terminal.
The polarity of AI Hold Complete Event 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.
Retriggerable Analog Input
The AI Start Trigger can also be configured to be retriggerable. The timing
engine will generate the sample and convert clocks for the configured
acquisition in response to each pulse on an AI Start Trigger signal.
The timing engine ignores the AI Start Trigger signal while the clock
generation is in progress. After the clock generation is finished, the counter
waits for another Start Trigger to begin another clock generation.
Figure 4-31 shows a retriggerable analog input with three AI channels and
four samples per trigger.
Figure 4-31. Simultaneous MIO X Series Retriggerable Analog Input
AI Start Trigger
AI Sample Clock
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