Example Application That Works Incorrectly (Duplicate Counting); Example Application That Prevents Duplicate Counting - National Instruments NI 660 Series User Manual

Chapter 2 Device Overview

Example Application That Works Incorrectly (Duplicate Counting)

In Figure 2-5, after the first rising edge of Gate, no Source pulses occur.
So the counter does not write the correct data to the buffer.

Example Application That Prevents Duplicate Counting

With duplicate count prevention enabled, the counter synchronizes
both the Source and Gate signals to the maximum onboard timebase.
By synchronizing to the timebase, the counter detects edges on the Gate
even if the Source does not pulse. This enables the correct current count to
be stored in the buffer even if no Source edges occur between Gate signals.
Figure 2-6 shows an example application that prevents duplicate counting.
Gate
Source
80 MHz Timebase
Counter Value 6
Buffer
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Gate
Source
Counter Value 6 7
Buffer
Figure 2-5. Example Application That Works Incorrectly
Counter detects
rising Gate edge.
7 0
7
Figure 2-6. Example Application That Prevents Duplicate Counting
2-6
No Source edge, so no
value written to buffer.
1
7
Counter value
increments only
one time for each
Source pulse.
1
0
7
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