User's Manual

You can route the pause trigger to the Gate input of the counter. You can

configure the counter to pause counting when the pause trigger is high or

when it is low. Figure 17 shows an example of on-demand edge counting

with a pause trigger.

Figure 17. Single-Point (On-Demand) Edge Counting with Pause Trigger

Buffered (Sample Clock) Edge Counting

With buffered edge counting (edge counting using a sample clock), the

counter counts the number of edges on the Source input after the counter is

armed. The value of the counter is sampled on each active edge of a sample

clock. The NI cDAQ-9172 transfers the sampled values to host memory.

The count values returned are the cumulative counts since the counter

armed event. That is, the sample clock does not reset the counter.

You can route the counter sample clock to the Gate input of the counter. You

can configure the counter to sample on the rising or falling edge of the

sample clock.

Figure 18 shows an example of buffered edge counting. Notice that

counting begins when the counter is armed, which occurs before the

first active edge on Gate.

Figure 18. Buffered (Sample Clock) Edge Counting

Counter Armed

SOURCE

Pause Trigger

(Pause When Low)

Counter Value

1 0 0 5 4 3 2

ounter Armed

SOURCE

Sample Clock

(Sample on Rising Edge)

Counter Value

Buffer

1 0 7 6 3 4 5 2