Chapter 9

Counters

The counter increments on each rising edge of channel A. The counter decrements on each rising edge of channel B, as shown in Figure 9-19.

Ch A

Ch B

Counter Value 2

3

4

5

4

3

4

Figure 9-19.Measurements Using Two Pulse Encoders

For information about connecting counter signals, refer to the Default

Counter/Timer Pinouts section.

Two-Signal Edge-Separation Measurement

Two-signal edge-separation measurement is similar to pulse-width measurement, except that there are two measurement signals—Aux and Gate. An active edge on the Aux input starts the counting and an active edge on the Gate input stops the counting. You must arm a counter to begin a two edge separation measurement.

After the counter has been armed and an active edge occurs on the Aux input, the counter counts the number of rising (or falling) edges on the Source. The counter ignores additional edges on the Aux input.

The counter stops counting upon receiving an active edge on the Gate input.

The counter stores the count in a hardware save register.

You can configure the rising or falling edge of the Aux input to be the active edge. You can configure the rising or falling edge of the Gate input to be the active edge.

Use this type of measurement to count events or measure the time that occurs between edges on two signals. This type of measurement is sometimes referred to as start/stop trigger measurement, second gate measurement, or A-to-B measurement.

Single Two-Signal Edge-Separation Measurement

With single two-signal edge-separation measurement, 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 and ignores other edges on its inputs. Software then reads the stored count.