© National Instruments
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5-3
NI cDAQ-9132/9133/9134/9135/9136/9137 User Manual
Counter Input Applications
The following sections list the various counter input applications available on the cDAQ
controller:
•
•
•
•
•
•
•
Counting Edges
In edge counting applications, the counter counts edges on its Source after the counter is armed.
You can configure the counter to count rising or falling edges on its Source input. You also can
control the direction of counting (up or down), as described in the
section. The counter values can be read on demand or with a sample clock.
Refer to the following sections for more information about edge counting options:
•
Single Point (On-Demand) Edge Counting
•
Buffered (Sample Clock) Edge Counting
Single Point (On-Demand) Edge Counting
With single point (on-demand) edge counting, the counter counts the number of edges on the
Source input after the counter is armed. On-demand refers to the fact that software can read the
counter contents at any time without disturbing the counting process. Figure 5-2 shows an
example of single point edge counting.
Figure 5-2.
Single Point (On-Demand) Edge Counting
Buffered Position
No
Yes
Buffered Two-Signal Edge Separation
Yes
Yes
Table 5-1.
Counter Timing Measurements (Continued)
Measurement
Implicit
Timing Support
Sample Clocked
Timing Support
Co
u
nter Armed
S
OURCE
Co
u
nter V
a
l
u
e
1
0
5
4
3
2
