Chapter 7
Counters
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National Instruments Corporation
7-5
Figure 7-5 shows an example of a single pulse-width measurement.
Figure 7-5.
Single Pulse-Width Measurement
Buffered Pulse-Width Measurement
Buffered pulse-width measurement is similar to single pulse-width
measurement, but buffered pulse-width measurement takes measurements
over multiple pulses.
The counter counts the number of edges on the Source input while the Gate
input remains active. On each trailing edge of the Gate signal, the counter
stores the count in a hardware save register. A DMA controller transfers the
stored values to host memory.
Figure 7-6 shows an example of a buffered pulse-width measurement.
Figure 7-6.
Buffered Pulse-Width Measurement
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
S
OURCE
GATE
Co
u
nter V
a
l
u
e
HW
Sa
ve Regi
s
ter
1
0
2
2
SOURCE
GATE
Counter Value
Buffer
1
0
3
3
2
2
1
2
3
3
2
