NI cDAQ-9178 - Page 62

NI cDAQ-9178/9174 User Guide and Specifications 62 ni.com
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/ReferenceTrigger)
• AI Start Trigger (ai/StartTrigger)
• 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.
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 NI cDAQ-9178/9174 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 (di/SampleClock)
• DO Sample Clock (do/SampleClock)
• AI Sample Clock (ai/SampleClock, te0/SampleClock, te1/SampleClock)
• AI Convert Clock (ai/ConvertClock)
• AO Sample Clock (ao/SampleClock)
• DI Change Detection output
Several other internal signals can be routed to Counter n Sample Clock through internal routes. Refer to
Device Routing in MAX in the NI-DAQmx Help or the LabVIEW Help for more information.
Using an External Source
You can route any of the following signals as Counter n Sample Clock:
• Any PFI terminal
• Analog Comparison Event
You can sample data on the rising or falling edge of Counter n Sample Clock.
Routing Counter n Sample Clock to an Output Terminal
You can route Counter n Sample Clock out to any PFI terminal. The PFI circuitry inverts the polarity of
Counter n Sample Clock before driving the PFI terminal.