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Chapter 7
Counters
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.
Counter input operations can use the arm start trigger to have start trigger-like behavior.
When using a start trigger, the start trigger source is routed to the Counter
n
Gate signal
input of the counter.
•
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 generations, the counter stops generating pulses while the external
trigger signal is low and resumes when the signal goes high or vice versa.
When using a pause trigger, the pause trigger source is routed to the Counter
n
Gate signal
input of the counter.
Other Counter Features
The following sections list the other counter features available on M Series devices.
Cascading Counters
You can internally route the Counter
n
Internal Output and Counter
n
TC signals of each counter
to the Gate inputs of the other counter. By cascading two counters together, you can effectively
create a 64-bit counter. By cascading counters, you also can enable other applications. For
example, to improve the accuracy of frequency measurements, use reciprocal frequency
measurement, as described in the
Large Range of Frequencies with Two Counters
section.
Counter Filters
You can enable a programmable debouncing filter on each PFI, RTSI, or PXI_STAR signal.
When the filters are enabled, your device samples the input on each rising edge of a filter clock.
M Series devices use an onboard oscillator to generate the filter clock with a 40 MHz frequency.
Note
NI-DAQmx
only
supports filters on counter inputs.
Summary of Contents for PCI-6281
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