Measurement Computing Data Translation DT9857 User Manual page 107

When synchronizing the analog input subsystems of multiple DT9857 modules, start the slave
modules before starting the master module. When the master DT9857 module is triggered
(using the software trigger, external digital trigger, or threshold trigger), both the master and
the slave modules start acquiring data at the same time (within one A/D conversion of the
clock). If you specified a reference trigger (external digital trigger or threshold trigger for the
master, and the Sync Bus for the slaves), the master and the slaves will start acquiring the
specified number of post-trigger scans when the reference trigger is detected on the master
(you must specify the number of post-trigger scan count for the master and the slaves). Note
that you can set the clock rate to be the same or different on each module but correlation of the
data will be difficult if the clock rates are not the same or are not multiples of each other.
Note: It is important that you start the slave modules first, followed by the master module
so that the slave receives the appropriate clock and trigger signals from the master.
If you start the master module before the slaves, the slaves never start; you will see a delay of
approximately 20 seconds if you try to stop or abort the analog input operation on a slave
module that is waiting for a trigger.
If you are not using a reference trigger and you stop the master module, the slaves continue to
run and return data until you stop the analog input subsystem on the slave modules. Be sure
to stop the analog input subsystems on all slave modules before disconnecting the cable from
the Sync Bus connectors.
Principles of Operation
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