Chapter 9

Counters

Figure 9-20shows an example of a single two-signal edge-separation measurement.

 

Counter

 

Armed

AUX

 

 

Measured Interval

 

 

 

 

 

 

 

 

 

 

GATE

 

 

 

 

 

SOURCE

 

 

 

 

 

Counter Value

0 0 0 0 1 2 3 4 5 6 7 8 8 8

HW Save Register

8

Figure 9-20.Single Two-Signal Edge-Separation Measurement

Buffered Two-Signal Edge-Separation Measurement

Buffered and single two-signal edge-separation measurements are similar, but buffered measurement measures multiple intervals.

The counter counts the number of rising (or falling) edges on the Source input occurring between an active edge of the Gate signal and an active edge of the Aux signal. The counter then stores the count in a hardware save register. On the next active edge of the Gate signal, the counter begins another measurement. A USB Signal Stream transfers the stored values to host memory.

Figure 9-21shows an example of a buffered two-signal edge-separation measurement.

AUX

 

 

 

 

 

 

 

 

GATE

 

 

 

 

 

 

 

 

SOURCE

 

 

 

 

 

 

 

 

Counter Value

1 2 3

1 2 3

1 2 3

 

 

 

 

3

 

3

 

3

 

Buffer

 

 

 

 

3

 

3

 

 

 

 

 

 

 

3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 9-21.Buffered Two-Signal Edge-Separation Measurement

For information about connecting counter signals, refer to the Default

Counter/Timer Pinouts section.

© National Instruments Corporation

9-19

NI USB-621x User Manual