National Instruments Welding System 321645c-01 Manual De Usuario
Chapter 2
Function Reference — GPCTR_Set_Application
©
National Instruments Corporation
2-237
NI-DAQ FRM for PC Compatibles
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
. You
can do this as follows:
Create u32 variable counter_armed.
repeat
{
GPCTR_Watch(deviceNumber, gpctrNumber, ND_ARMED, counter_armed)
}
until (counter_armed = ND_NO)
When the counter is disarmed, you can safely access data in the buffer.
Typically, you will find modifying the following parameters through the
GPCTR_Change_Parameter
function useful when the counter application is
ND_BUFFERED_EVENT_CNT
. You can change the following:
•
ND_SOURCE
to any legal value listed in the
GPCTR_Change_Parameter
function
description.
•
ND_SOURCE_POLARITY
to
ND_HIGH_TO_LOW
.
•
ND_GATE
to any legal value listed in the
GPCTR_Change_Parameter
function
description.
•
ND_GATE_POLARITY
to
ND_NEGATIVE
. Counts will be captured on every high-to-low
transition of the signal present at the gate.
Note
The counter will start counting as soon as you arm it. However, it will not count
if the gate signal stays in low state when
if the gate signal stays in low state when
ND_GATE_POLARITY
is
ND_POSITIVE
or if it stays in high state when
ND_GATE_POLARITY
is
ND_NEGATIVE
while
GPCTR_Control
is executed with action
= ND_ARM
or action
= ND_PROGRAM
.
Be aware of this when you interpret the first count in your buffer.
application =
ND_BUFFERED_PERIOD_MSR
In this application, the counter is used for continuous measurement of the time interval
between successive transitions of the same polarity of the gate signal. By default, those are
the low-to-high transitions of the signal listed in Table 2-25. The counter counts the 20 MHz
internal timebase (
between successive transitions of the same polarity of the gate signal. By default, those are
the low-to-high transitions of the signal listed in Table 2-25. The counter counts the 20 MHz
internal timebase (
ND_INTERNAL_20_MHZ
), so the resolution of measurement is 50 ns. The
counter counts up starting from 0; its contents are placed in the buffer after an edge of
appropriate polarity is detected on the gate; the counter then starts counting up from 0 again.
NI-DAQ transfers data from the counter into the buffer until the buffer is filled; the counter is
disarmed at that time.
appropriate polarity is detected on the gate; the counter then starts counting up from 0 again.
NI-DAQ transfers data from the counter into the buffer until the buffer is filled; the counter is
disarmed at that time.
The default 20 MHz timebase, combined with the counter width for E Series and 445X
devices (24 bits), lets you measure the width of a pulse between 100 ns and 0.8 s long. For
devices (24 bits), lets you measure the width of a pulse between 100 ns and 0.8 s long. For