Triggering; Triggering With A Digital Source - National Instruments NI USB-621x User Manual

Triggering

Triggering with a Digital Source

© National Instruments Corporation
A trigger is a signal that causes an action, such as starting or stopping the
acquisition of data. When you configure a trigger, you must decide how you
want to produce the trigger and the action you want the trigger to cause. All
M Series devices support internal software triggering, as well as external
digital triggering. For information about the different actions triggers can
perform for each sub-system of the device, refer to the following sections:
• The Analog Input Digital Triggering
Input
• The Analog Output Digital Triggering
Output
• The Counter Triggering
Your DAQ device can generate a trigger on a digital signal. You must
specify a source and an edge. The digital source can be any input PFI signal.
The edge can be either the rising edge or falling edge of the digital signal.
A rising edge is a transition from a low logic level to a high logic level. A
falling edge is a high to low transition.
Figure 14-1 shows a falling-edge trigger.
Digital Trigger
14-1
section of Chapter 4,
section of Chapter 7,
section of Chapter 9,
5 V
Falling Edge Initiates Acquisition
Figure 14-1. Falling-Edge Trigger
14
Analog
Analog
Counters
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NI USB-621x User Manual