© National Instruments | 4-11
NI cDAQ-9181/9184/9188/9191 User Manual
DO Sample Clock Timebase Signal
The DO Sample Clock Timebase (do/SampleClockTimebase) signal is divided down to provide
a source for DO Sample Clock. DO Sample Clock Timebase can be generated from external or
internal sources, and is not available as an output from the chassis.
DO Start Trigger Signal
Use the DO Start Trigger (do/StartTrigger) signal to initiate a waveform generation. If you do
not use triggers, you can begin a generation with a software command. If you are using an
internal sample clock, you can specify a delay from the start trigger to the first sample. For more
information, refer to the NI-DAQmx Help.
Using a Digital Source
To use DO Start Trigger, specify a source and a rising or falling edge. The source can be one of
the following signals:
• A pulse initiated by host software
• Any PFI terminal
• AI Reference Trigger
• AI Start Trigger
The source also can be one of several internal signals on the cDAQ chassis. Refer to the Device
Routing in MAX topic in the NI-DAQmx Help or the LabVIEW Help for more information.
You also can specify whether the waveform generation begins on the rising edge or falling edge
of DO Start Trigger.
Using an Analog Source
Some C Series 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 waveform generation begins on the first rising or
falling edge of the Analog Comparison Event signal, 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 module capabilities, you may need two modules
to utilize analog triggering.
Routing DO Start Trigger Signal to an Output Terminal
You can route DO Start Trigger to any output PFI terminal. The output is an active high pulse.
DO Pause Trigger Signal
Use the DO Pause Trigger signal (do/PauseTrigger) to mask off samples in a DAQ sequence.
When DO Pause Trigger is active, no samples occur, but DO Pause Trigger does not stop a
sample that is in progress. The pause does not take effect until the beginning of the next sample.
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