Example Application That Works Incorrectly (Duplicate Counting); Example Application That Prevents Duplicate Count - National Instruments NI 6221 User Manual

Chapter 7 Counters
Counter Value
M Series User Manual
The counter synchronizes or samples the Gate signal with the Source
signal, so the counter does not detect a rising edge in the 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. Synchronization modes are described in the
Synchronization Modes
Example Application That Works Incorrectly
(Duplicate Counting)
In Figure 7-31, after the first rising edge of Gate, no Source pulses occur,
so the counter does not write the correct data to the buffer.
Gate
Source
6 7
Buffer

Example Application That Prevents Duplicate Count

With duplicate count prevention enabled, the counter synchronizes both the
Source and Gate signals to the 80 MHz 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, as shown in Figure 7-32.
section.
No Source edge, so no
value written to buffer.
Figure 7-31. Duplicate Count Example
7-36
1
7
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