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I want to use several modules for a DAQ.I'm in multiplexed mode so I think I only need one board. But I wonder how can I synchronize the modules to start DAQ at the same time.

There are 3 ideas that come to mind to synchronous operations:
1. For perfect synchronous clocking, use an external synch-pulse generator that inputs directly to the modules (if they are configurable for such). We often use this setup to allow a clock to control the timing of module functions, such as synchronous data transmissions.
2. A second option (but may insert micro-seconds of delays between each module) is have Labview synchronize the operations by putting all your modules' independent functions (e.g. Read, Write...) in Case statements, and as soon as the Case receives a T (or F), perform the functions. The T/F's sent to the Cases is in essence your clock.
Ex: Only when a True is sent to the Case will all the modules 'Write to port'; if F, do nothing.
The True could come from a "Wait Until Next ms Multiple" VI and perhaps 100 input so that every .1 seconds you will Write data.
3. Check into the Labview Realtime processor too, as well as multi-threading options.

Good Luck, Doug
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