National Instruments 321645c-01 用户手册
Chapter 2
Function Reference — GPCTR_Set_Application
NI-DAQ FRM for PC Compatibles
2-226
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National Instruments Corporation
Figure 2-18 shows one possible use of a counter for
ND_TWO_SIGNAL_EDGE_SEPARATION_MSR
after the following programming sequence:
GPCTR_Control (deviceNumber, gpctrNum, ND_RESET)
GPCTR_Set_Application (deviceNumber, gpctrNum,
ND_TWO_SIGNAL_EDGE_SEPARATION_MSR)
GPCTR_Control (deviceNumber, gpctrNum, ND_PROGRAM)
In Figure 2-18, the following behavior is present:
•
Gate is the signal present at the counter gate input.
•
Second Gate is the signal present at the counter second gate input.
•
Source is the signal present at the counter source input.
•
Count is the value you would read from the counter if you called the
GPCTR_Watch
function entityID =
ND_COUNT
. The different numbers illustrate the behavior at different
times.
•
Armed is the value you would read from the counter if you called the
GPCTR_Watch
function with entityID =
ND_ARMED
. The different values illustrate behavior at different
times.
Figure 2-18. Start-Stop Measurement
Use the
GPCTR_Watch
function with entityID =
ND_ARMED
to monitor the progress of the
counting process. This measurement completes when entityValue becomes
ND_NO
. When the
counter is no longer armed, you can retrieve the counted value by using
GPCTR_Watch
with
entityID =
ND_COUNT
, as shown in the following example code:
Create U32 variable counter_armed.
Create U32 variable counter_value.
repeat
Source
Count
Armed
3
Second Gate
Gate
1
0
YES
YES
YES
2
3
3
3
3
3
3
3
3
3
NO
NO
NO
NO
NO
NO
NO
NO