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Chapter 2 Function Reference — DAQ_StopTrigger_Config
NI-DAQ FRM for PC Compatibles 2-140
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National Instruments Corporation
DAQ_StopTrigger_Config
Format
status = DAQ_StopTrigger_Config (deviceNumber, stopTrig, ptsAfterStoptrig)
Purpose
Enables the pretrigger mode of data acquisition and indicates the number of data points
to acquire after NI-DAQ applies the stop trigger pulse at the STOPTRIG* input of the
MIO-16/16D; the EXTTRIG* input of an AT-MIO-16F-5, AT-MIO-64F-5, or AT-MIO-16X
or the EXTTRIG input of Lab and 1200 Series devices; or the PFI1 pin. Refer to the PFI1 pin
of an E Series device. If you are using an E Series device, see the
Select_Signal
description for information about the external timing signals.
Parameters
Input
Parameter Discussion
stopTrig indicates whether to enable or disable the pretriggered mode of data acquisition.
0: Disable pretrigger (the default).
1: Enable pretrigger.
ptsAfterStoptrig is the number of data points to acquire after the trigger. This parameter is
valid only if stopTrig equals 1. For a multiple channel scanned acquisition, ptsAfterStoptrig
must be an integer multiple of the number of channels scanned.
Range: 3 through count, where count is the value of the count parameter in the Start call
used to start the acquisition. For Lab and 1200 Series devices, the maximum is
always 65,535. For an E Series device or DSA device, the range is 2 through
count.
Using This Function
Calling DAQ_StopTrigger_Config with the stopTrig parameter set to 1 causes any
subsequent Start call to initiate a cyclical mode data acquisition. In this mode, NI-DAQ
writes data continually into your buffer, overwriting data at the beginning of the buffer when
NI-DAQ has filled the entire buffer. You can use
DAQ_Check or Lab_ISCAN_Check in this
situation to determine where NI-DAQ is currently depositing data in the buffer. When you
Name Type Description
deviceNumber i16 assigned by configuration utility
stopTrig i16 enable or disable the pretriggered mode
ptsAfterStoptrig u32 number of points to acquire after the trigger