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Chan 2
Chan 1
Chan 0
Input
Sample
Clock
Pre-trigger data acquired
Start Trigger occurs
Figure 23: Continuous Scan Mode on the DT9837 Series Modules
Input Triggers
A trigger is an event that occurs based on a specified set of conditions.
On the DT9837 Series modules, you can specify a start trigger source and a reference trigger
source. Pre-trigger data acquisition starts when the start trigger event occurs. When the
reference trigger event occurs, pre-trigger data acquisition stops and post-trigger acquisition
starts. Post-trigger acquisition stops when the number of samples you specify for the
post-trigger scan count has been reached. Refer to
Start Trigger Sources
The DT9837 Series modules support the following sources for the start trigger:
• Software trigger – A software trigger event occurs when you start the analog input
operation (the computer issues a write to the module to begin conversions). Using
software, specify the start trigger source as a software trigger.
• External digital (TTL) trigger – An external digital (TTL) trigger event occurs when the
module detects a rising-edge transition on the signal connected to the Ext Trig connector
on the module. Using software, specify the start trigger source as an external, positive
digital (TTL) trigger.
Note: On the DT9837A, DT9837B, and DT9837C modules, if you configure the
synchronization mode as slave, the RJ45 connector accepts trigger and clock signals from
the master; you cannot use the Ext Trig connector on the slave module. Refer to
for more information.
Trigger Sample is not counted
as post-trigger sample
Chan 2
Chan 2
Chan 1
Chan 1
Chan 0
Chan 0
Reference Trigger occurs
Using a Start and Reference Trigger
Post-Trigger Scan Count = 3
Chan 2
Chan 2
Chan 1
Chan 1
Chan 0
Chan 0
3 Post-trigger samples acquired
page 71
for more information.
Principles of Operation
Chan 2
Chan 1
Chan 0
page 87
73
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