Triggering With A Digital Source - National Instruments NI 6221 User Manual

Triggering
Note Not all M Series devices support analog triggering. For more information about
triggering compatibility, refer to the specifications document for your device.

Triggering with a Digital Source

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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. Some devices also support analog 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 Triggering
• The Analog Output Triggering
• 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 of the PFI,
RTSI, or PXI_STAR signals.
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 11-1 shows a falling-edge trigger.
Digital Trigger
11-1
section of Chapter 4,
section of Chapter 5,
section of Chapter 7,
5 V
Falling Edge Initiates Acquisition
Figure 11-1. Falling-Edge Trigger
11
Analog Input
Analog Output
Counters
0 V
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