Chapter 9

Counters

The counters have seven input signals, although in most applications only a few inputs are used.

For information about connecting counter signals, refer to the Default

Counter/Timer Pinouts section.

Counter Input Applications

Counting Edges

In edge counting applications, the counter counts edges on its Source after the counter is armed. You can configure the counter to count rising or falling edges on its Source input. You also can control the direction of counting (up or down).

The counter values can be read on demand or with a sample clock.

Single Point (On-Demand) Edge Counting

With single point (on-demand) edge counting, the counter counts the number of edges on the Source input after the counter is armed. On-demandrefers to the fact that software can read the counter contents at any time without disturbing the counting process. Figure 9-2shows an example of single point edge counting.

Counter Armed

SOURCE

Counter Value

0

1

2

3

4

5

Figure 9-2.Single Point (On-Demand) Edge Counting

You also can use a pause trigger to pause (or gate) the counter. When the pause trigger is active, the counter ignores edges on its Source input. When the pause trigger is inactive, the counter counts edges normally.

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 9-3shows an example of on-demand edge counting with a pause trigger.