Chapter 9

Counters

Counter Armed

 

 

 

 

 

 

 

 

GATE

 

 

 

 

 

 

 

 

SOURCE

 

 

 

 

 

 

 

 

Counter Value

 

1

2

3

1

2

3

1

 

 

 

 

 

3 3

 

 

3 3

Buffer

 

 

 

 

 

 

 

3

 

 

 

 

 

 

 

 

Time N

 

 

 

 

 

 

 

 

t0

t1

 

 

 

t2

 

 

t3

 

Figure 9-9.Buffered Period Measurement

 

Table 9-1.Time N Descriptions

 

 

t0

At t0, the counter is armed. No measurements are taken until

 

the counter is armed.

 

 

t1

The rising edge of Gate indicates the beginning of the first

 

period to measure. The counter begins counting rising edges of

 

Source.

 

 

t2

The rising edge of Gate indicates the end of the first period. The

 

USB M Series device stores the counter value in the buffer.

 

 

t3

The rising edge of Gate indicates the end of the second period.

 

The USB M Series device stores the counter value in the buffer.

 

 

Note that if you are using an external signal as the Source, at least one Source pulse should occur between each active edge of the Gate signal. This condition ensures that correct values are returned by the counter. If this condition is not met, the counter returns a zero. Refer to the Duplicate Count Prevention section for more information.

For information about connecting counter signals, refer to the Default

Counter/Timer Pinouts section.