National Instruments PCI-6601, Руководство пользователя

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Chapter 2 Device Overview
© National Instruments 2-5 NI 660x User Manual
Example Application That Works Correctly (No Duplicate Counting)
Fig
u
re 2-4 shows an external b
u
ffered signal as the period meas
u
rement
So
u
rce.
Figure 2-4. Example Application That Works Correctly
On the first rising edge of the Gate, the c
u
rrent co
u
nt of 7 is stored. On the
next rising edge of the Gate, the co
u
nter stores a 2 beca
u
se two So
u
rce
p
u
lses occ
u
rred after the previo
u
s rising edge of Gate.
The co
u
nter synchronizes or samples the Gate signal with the So
u
rce
signal. So the co
u
nter does not detect a rising edge in the Gate
u
ntil the next
So
u
rce p
u
lse. In this example, the co
u
nter stores the val
u
es in the b
u
ffer on
the first rising So
u
rce edge after the rising edge of Gate.
Gate
Source
Counter Value
Buffer
2
7 7
6 7 1 2 1
Rising Edge
of Gate
Counter detects rising edge
of Gate on the next rising
edge of Source.