Sharing a clock with multiple cards

[MikeGI]

Hello,

I am using Matlab to capture period gate events through two 6602 Cards.  An RTSI cable is connected to them and setup up through MAX.  I am trying to sychronize the cards by send the master card clock to the slave card.  I have tried many different approaches, mainly DAQmxSetMasterTimebaseSrc and ExportSignal.  I can't seem to get these functions to work without error.  I would explain what I have tried but it would just be too long and probably not very helpful.  Since the RTSI is only capable of carrying the 20 MHz clock, does anyone know how to make two cards share one 20 MHz clock?

-Mike

[stilly32]

Hi Mark,

For a 6602, you'll want to use the DAQmxSetCICtrTimebaseSrc() and DAQmxSetCICtrTimebaseRate() properties, and ensure that the terminals for both cards are the same, ie "/6602A/20MHzTimebase". DAQmx will take care of the routing across RTSI as long as you have the devices added to the RTSI connector in MAX. If this doesn't work, what kind of errors are you seeing (numbers, screenshots...). Also, do you really need the timebases sync'd for period measurements? They're going to have the same error regardless of the timebase being used and in fact you're limiting your resolution by requiring the cards to use the 20MHz clock instead of the 80Mhz. In most cases I've run across sharing a start trigger is sufficient.

Hope this helps,

Andrew S

[MikeGI]

Hello,

Thanks, I actually had been using these functions.  The problem existed in my signal generator.  These functions do the job.  I need both cards synced on the same clock to prevent drifting.  If one card has a 19.98 MHz clock and the other had a 20.02 MHz clock, the amount of ticks will eventually increase in difference.  Using the same clock will prevent this (hopefully).  And I do also use a start trigger.