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Chapter 2

Function Reference — GPCTR_Set_Application

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

{

Gate

Source

Count

Count Available

Measured

Interval

YES