Chapter 7
Counters
©
National Instruments Corporation
7-35
Example Application That Works Correctly
(No Duplicate Counting)
Figure 7-32 shows an external buffered signal as the period measurement
Source.
Figure 7-32.
Duplicate Count Prevention Example
On the first rising edge of the Gate, the current count of 7 is stored. On the
next rising edge of the 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 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
section.
2
7
7
6 7 1
2
1
Ri
s
ing Edge
of G
a
te
Co
u
nter detect
s
ri
s
ing
edge of G
a
te on the next
ri
s
ing edge of
S
o
u
rce.
S
o
u
rce
G
a
te
B
u
ffer
Co
u
nter V
a
l
u
e
