Data Translation DT9820 Series, User Manual

Page: 33 / 112

Principles of Operation
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• External trigger
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Using software, specify the trigger source for
the first A/D subsystem (lowest subsystem number) that you
want to start simultaneously as an external digital (TTL) trigger.
Then, wire the appropriate external digital line, as listed in
Table
4 on page 14 , to that A/D subsystem.
For example, if you want to trigger A/D subsystems 0 and 1
simultaneously, wire the digital source to digital input line 0 (do
not wire the digital source to digital input line 1). Using software,
allocate a start list, put the A/D subsystems on the start list,
prestart the subsystems, then start the subsystems. When started,
the subsystems are triggered simultaneously when a high-to-low
transition occurs on digital input line 0.
Similarly, if you want to trigger A/D subsystems 2 and 3
simultaneously, wire the digital source to digital input line 2 (do
not wire the digital source to digital input line 3). Using software,
allocate a start list, put the A/D subsystems on the start list,
prestart the subsystems, then start the subsystems. When started,
the subsystems are triggered simultaneously when a high-to-low
transition occurs on digital input line 2.
Refer to the example programs on the Data Acq OMNI CD for an
example of synchronizing subsystems using an external trigger.
Note: To achieve more flexibility, you can simultaneous start two
channels, and once started, simultaneously start the other two
channels, if desired.