To Next Page

To Previous Page

Chapter 9 Counters

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 8.x Help for more information

about how to connect your signals for common counter measurements and

generations. M Series default PFI lines for counter functions are listed in

Physical Channels in the NI-DAQmx Help or the LabVIEW 8.x Help.

Counter Triggering

Counters support three different triggering actions—arm start, start, and

pause.

Arm Start Trigger

Any counter operation can use the arm start trigger.

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

National Instruments NI USB-621x User Manual

Questions and Answers: