National Instruments 321645c-01 用户手册

Chapter 2

Function Reference — GPCTR_Set_Application

NI-DAQ FRM for PC Compatibles

2-228

National Instruments Corporation

For example, assume that you want to generate a pulse 200 ns long after 150 ns of delay.
You need to set

ND_COUNT_1

to 150 ns/50 ns = 3 and

ND_COUNT_2

to 200 ns/50 ns = 4.

Figure 2-19 shows the scenario of a counter used for

ND_SINGLE_PULSE_GNR

after the

following programming sequence:

GPCTR_Control(deviceNumber, gpctrNum, ND_RESET)

GPCTR_Set_Application(deviceNumber, gpctrNum, ND_SINGLE_PULSE_GNR)

GPCTR_Change_Parameter(deviceNumber, gpctrNum, ND_COUNT_1, 3)

GPCTR_Change_Parameter(deviceNumber, gpctrNum, ND_COUNT_2, 4)

Select_Signal(deviceNumber, gpctrNumOut, gpctrNumOut,ND_LOW_TO_HIGH)

GPCTR_Control(deviceNumber, gpctrNum, ND_PROGRAM)

In Figure 2-19, the following behavior is present:

•

Source is the signal present at the counter source input.

•

Output is the signal present at the counter output.

•

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 2-19. Single Pulse Generation

Use the

GPCTR_Watch

function with entityID =

ND_ARMED

to monitor the progress of the

pulse generation process. The generation completes when entityValue becomes

ND_NO

Typically, you find modifying of the following parameters through the

GPCTR_Change_Parameter

function useful when the counter application is

ND_SINGLE_PERIOD_MSR

. You can change the following:

•

ND_COUNT_1

and

ND_COUNT_2

to any value between 2 and 2

– 1 for E Series and 445X

devices, and to any value between 2

– 1 for 6602 and 455X devices. The defaults are

given for illustrative purposes only.

•

ND_SOURCE

ND_INTERNAL_100_KHZ

. With this timebase, you can generate pulses

with a delay and length between 20 µs and 160 s for E Series and 445X devices and

Source

Armed

Output

Count_1 = 3

Count_2 = 4

Yes