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Chapter 5 Counters
other applications, such as single pulse-width measurement, the counter begins waiting for the
Gate signal when it is armed. Counter output operations can use the arm signal in addition to a
start trigger.
Software can arm a counter or configure counters to be armed on a hardware signal. Software
calls this hardware signal the Arm Start Trigger. Internally, software routes the Arm Start Trigger
to the Counter n HW Arm input of the counter.
Routing Signals to Counter n HW Arm Input
Any of the following signals can be routed to the Counter n HW Arm input:
• Any PFI terminal
• AI Reference Trigger
• AI Start Trigger
• Analog Comparison Event
• Change Detection Event
A counter’s Internal Output can be routed to a different counter’s HW Arm.
Some of these options may not be available in some driver software. Refer to the Device Routing
in MAX topic in the NI-DAQmx Help or the LabVIEW Help for more information about available
routing options.
Counter n Sample Clock Signal
Use the Counter n Sample Clock (CtrnSampleClock) signal to perform sample clocked
acquisitions and generations.
You can specify an internal or external source for Counter n Sample Clock. You also can specify
whether the measurement sample begins on the rising edge or falling edge of Counter n Sample
Clock.
If the cDAQ chassis receives a Counter n Sample Clock when the FIFO is full, it reports an
overflow error to the host software.
Using an Internal Source
To use Counter n Sample Clock with an internal source, specify the signal source and the
polarity of the signal. The source can be any of the following signals:
• DI Sample Clock
• DO Sample Clock
• AI Sample Clock (ai/SampleClock, te0/SampleClock, te1/SampleClock)
• AI Convert Clock
• AO Sample Clock
• DI Change Detection output
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