Chapter 9

Counters

Example Application That Works Correctly

(No Duplicate Counting)

Figure 9-32shows an external buffered signal as the period measurement

Source.

 

 

 

 

 

Rising Edge

 

 

 

 

 

of Gate

 

 

 

 

 

Counter detects rising edge

 

 

 

 

 

of Gate on the next rising

 

 

 

 

 

edge of Source.

Gate

 

 

 

 

 

Source

 

 

 

 

 

Counter Value

6

7

1

2

1

Buffer

 

 

7

 

2

 

 

 

 

 

7

Figure 9-32.Duplicate Count Prevention Example

On the first rising edge of Gate, the current count of 7 is stored. On the next rising edge of Gate, the counter stores a 2 since two Source pulses occurred after the previous rising edge of Gate.

The counter synchronizes or samples the Gate signal with the Source signal, so the counter does not detect a rising edge in Gate until the next Source pulse. In this example, the counter stores the values in the buffer on the first rising Source edge after the rising edge of Gate. The details of when exactly the counter synchronizes the Gate signal vary depending on the synchronization mode.