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Chapter 2 Function Reference — GPCTR_Set_Application
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National Instruments Corporation 2-221 NI-DAQ FRM for PC Compatibles
measure a time interval between 100 ns and 0.8 s long.For the 6602 and 455X devices with
counter width 32 bits, you can measure a time interval between 100 ns and 214 s long.
Figure 2-16 shows one possible scenario of a counter used for
ND_SINGLE_PULSE_WIDTH_MSR after the following programming sequence:
GPCTR_Control(deviceNumber, gpctrNum, ND_RESET)
GPCTR_Set_Application(deviceNumber, gpctrNum,
ND_SINGLE_PULSE_WIDTH_MSR)
GPCTR_Control(deviceNumber, gpctrNum, ND_PROGRAM)
In Figure 2-16, the following behavior is present:
• Gate is the signal present at the counter 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 with entityID =
ND_COUNT. The different numbers illustrate behavior at
different times.
• Count Available is the value you would read from the counter if you called the
GPCTR_Watch function with entityID = ND_COUNT_AVAILABLE. The different values
illustrate behavior at different times.
Figure 2-16.
Single Pulse Width 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 count_available.
Create u32 variable counted_value.
repeat
{
01
NO
NO
2
Gate
Source
Count
Count Available
Measured
Interval
YES
YES
2
2
2
2
2