Chapter 8 Counters
NI USB-621x User Manual 8-24 ni.com
You also can use the Gate input of the counter as a Pause Trigger (if it is not 
used as a Start Trigger). The counter pauses pulse generation when the 
Pause Trigger is active.
Figure 8-25 shows a continuous pulse train generation (using the rising 
edge of Source).
Figure 8-25.  Continuous Pulse Train Generation
Continuous pulse train generation is sometimes called frequency division. 
If the high and low pulse widths of the output signal are M and N periods, 
then the frequency of the Counter n Internal Output signal is equal to the 
frequency of the Source input divided by M + N.
For information about connecting counter signals, refer to the Default 
Counter/Timer Pinouts section.
Finite Pulse Train Generation
This function generates a train of pulses of predetermined duration. This 
counter operation requires both counters. The first counter (for this 
example, Counter 0) generates a pulse of desired width. The second 
counter, Counter 1, generates the pulse train, which is gated by the pulse of 
the first counter. The routing is done internally. Figure 8-26 shows an 
example finite pulse train timing diagram.
Figure 8-26.  Finite Pulse Train Timing Diagram
Counter 0
(Paired Counter)
Counter 1
Generation
Complete