© National Instruments Corporation 63 NI cDAQ-9178/9174 User Guide and Specifications
Counter n Internal Output and Counter n TC Signals
The Counter n Internal Output signal changes in response to Counter n TC.
The two software-selectable output options are pulse output on TC and toggle output on TC. The output
polarity is software-selectable for both options.
With pulse or pulse train generation tasks, the counter drives the pulse(s) on the Counter n Internal
Output signal. The Counter n Internal Output signal can be internally routed to be a counter/timer input
or an “external” source for AI, AO, DI, or DO timing signals.
Routing Counter n Internal Output to an Output Terminal
You can route Counter n Internal Output to any PFI terminal.
Frequency Output Signal
The Frequency Output (FREQ OUT) signal is the output of the frequency output generator.
Routing Frequency Output to a Terminal
You can route Frequency Output to any PFI terminal.
Default Counter/Timer Routing
Counter/timer signals are available to correlated digital I/O C Series modules. To determine the signal
routing options for modules installed in your system, refer to the Device Routes tab in MAX.
You can use these defaults or select other sources and destinations for the counter/timer signals in
NI-DAQmx. Refer to Connecting Counter Signals in the NI-DAQmx Help or the LabVIEW Help for
more information about how to connect your signals for common counter measurements and
generations. NI cDAQ-9178/9174 default PFI lines for counter functions are listed in Physical Channels
in the NI-DAQmx Help or the LabVIEW Help.
Counter Triggering
Counters support three different triggering actions:
• Arm Start Trigger—To begin any counter input or output function, you must first enable, or arm,
the counter. 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.
For counter output operations, you can use it in addition to the start and pause triggers. For counter
input operations, you can use the arm start trigger to have start trigger-like behavior. The arm start
trigger can be used for synchronizing multiple counter input and output tasks.
When using an arm start trigger, the arm start trigger source is routed to the Counter n HW Arm
signal.
• Start Trigger—For counter output operations, a start trigger can be configured to begin a finite or
continuous pulse generation. Once a continuous generation has triggered, the pulses continue to
generate until you stop the operation in software. For finite generations, the specified number of
pulses is generated and the generation stops unless you use the retriggerable attribute. When you
use this attribute, subsequent start triggers cause the generation to restart.
When using a start trigger, the start trigger source is routed to the Counter n Gate signal input of
the counter. Counter input operations can use the arm start trigger to have start trigger-like behavior.
• Pause Trigger—You can use pause triggers in edge counting and continuous pulse generation
applications. For edge counting acquisitions, the counter stops counting edges while the external
trigger signal is low and resumes when the signal goes high or vice versa. For continuous pulse
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