National Instruments Data Acquisition Device NI USB-621x - Manual (Page 55)

Chapter 4 Analog Input
NI USB-621x User Manual 4-22 ni.com
Using a Digital Source
To use AI Reference Trigger with a digital source, specify a source and an
edge. The source can be any input PFI signal.
The source also can be one of several 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 stops on the
rising edge or falling edge of AI Reference Trigger.
Routing AI Reference Trigger to an Output Terminal
You can route AI Reference Trigger out to any output PFI terminal.
AI Pause Trigger Signal
You can use the AI Pause Trigger (ai/PauseTrigger) signal to pause and
resume a measurement acquisition. The internal sample clock pauses while
the external trigger signal is active and resumes when the signal is inactive.
You can program the active level of the pause trigger to be high or low.
Using a Digital Source
To use AI Sample Clock, specify a source and a polarity. The source can
be any input PFI signal.
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.
Getting Started with AI Applications in Software
You can use the USB-621x device in the following analog input
applications:
• Single-point analog input
• Finite analog input
• Continuous analog input
You can perform these applications through DMA, interrupt, or
programmed I/O data transfer mechanisms. Some of the applications
also use start, reference, and pause triggers.