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Chapter 4
Digital Input/Output and PFI
If you are using any signal other than the onboard clock as the source of the sample clock, the
generation resumes as soon as the pause trigger is deasserted and another edge of the sample
clock is received, as shown in Figure 4-6.
Figure 4-6.
DO Pause Trigger with Other Signal Source
Using a Digital Source
To use DO Pause Trigger, specify a source and a polarity. The source can be a PFI signal or one
of several other internal signals on the cDAQ chassis.
You also can specify whether the samples are paused when DO Pause Trigger is at a logic high
or low level. Refer to the
Device Routing in MAX
topic in the
NI-DAQmx Help
or the
LabVIEW Help
for more information.
Using an Analog Source
Some C Series I/O modules can generate a trigger based on an analog signal. In NI-DAQmx, this
is called the Analog Comparison Event, depending on the trigger properties.
When you use an analog trigger source, the samples are paused when the Analog Comparison
Event signal is at a high or low level, depending on the trigger properties. The analog trigger
circuit must be configured by a simultaneously running analog input task.
Note
Depending on the C Series I/O module capabilities, you may need
two modules to utilize analog triggering.
Getting Started with DO Applications in Software
You can use the cDAQ chassis in the following digital output applications:
•
Single-point (on-demand) generation
•
Finite generation
•
Continuous generation
For more information about programming digital output applications and triggers in software,
refer the
LabVIEW Help
or to the
NI-DAQmx Help
.
Digital Input/Output Configuration for NI 9401
When you change the configuration of lines on a NI 9401 digital I/O module between input and
output, NI-DAQmx temporarily reserves all of the lines on the module for communication to
Pause Trigger
Sample Clock
