National Instruments Welding System 321645c-01 Manual De Usuario

Chapter 2

Function Reference — GPCTR_Set_Application

NI-DAQ FRM for PC Compatibles

2-232

National Instruments Corporation

Figure 2-21. Retriggerable Pulse Generation

Use the

GPCTR_Control

function with action =

ND_RESET

to stop the pulse generation.

Typically, you will find modifying the following parameters through the

GPCTR_Change_Parameter

function useful when the counter application is

ND_RETRIG_PULSE_GNR

. You can change the following:

•

ND_COUNT_1

and

ND_COUNT_2

to any value between 2 and 2

– 1. The defaults are

given for illustrative purposes only.

•

ND_SOURCE

ND_INTERNAL_100_KHZ

. With this timebase, you can generate pulses

with delay and length between 20 µs and 160 s. The timing resolution will be lower than
if you are using

ND_INTERNAL_20_MHZ

timebase.

•

ND_GATE

to any legal value listed in the

GPCTR_Change_Parameter

function

description.

•

ND_GATE_POLARITY

ND_NEGATIVE

. A high-to-low transition of the gate signal

initiates the pulse generation timing.

You can use the

GPCTR_Change_Parameter

function after calling

GPCTR_Set_Application

and before calling

GPCTR_Control

with

action =

ND_PROGRAM

ND_PREPARE

To provide your timebase, you can connect your timebase source to one of the PFI pins on the
I/O connector and change

ND_SOURCE

and

ND_SOURCE_POLARITY

to the appropriate values.

You also can configure the other general-purpose counter for

ND_RETRIG_PULSE_GNR

, and

set

ND_SOURCE

of this counter to

ND_OTHER_GPCTR_TC

to generate pulses with delays and

intervals longer than 160 s.

application =

ND_PULSE_TRAIN_GNR

In this application, the counter is used for generation of a pulse train. By default, you get this
by using the 20 MHz internal timebase (

ND_INTERNAL_20_MHZ

), so the resolution of timing

is 50 ns. By default, the counter repeatedly counts down from

ND_COUNT_1

= 5 million to 0

for the delay time and then down from

ND_COUNT_2

= 10 million to 0 for the pulse generation

time to generate a train of 0.5 s pulses separated by 0.25 s of delay. Pulse train generation
starts as soon as you arm the counter. You must reset the counter to stop the pulse train.

Source

Gate

Output

Count_1=3

Count_2=4

Count_1=3

Count_2=4

Count_1=3

Count_2=4