Multiple RSeries FPGA cards Synchronisation

[JK1]

Hai,

I have a PXI - 1044 with 2 FPGA RSeries (7831R) cards plugged into it.  The system is a part of closed loop control that sends out 'analog outputs' as the control signal with respect to feed back section.  A critical requirement is to achieve greater level of sycn between the control signals generated by the FPGA Cards.  The control must start synchronously from both cards after the control data is fed to FPGA from RT.  Pleas throw out your ideas on this application.

Thanks for all help.

With regards

JK

Message Edited by JK1 on 06-22-2007 08:40 AM

[Yi Y]

Hi JK1,

Below is a screenshot of one method we can use for synchronization.
The idea is that we split the operation to master and slave portion.  The master portion of the code compiles onto one card and the slave portion compiles onto the other card.
Since all the trigger lines on the back of the PXI plane is shared between all modules on your PXI chassis, we can use the PXI clock to control writing to the trigger lines.  We use triggering to synchronize the two cards.
The synchronization should be within several clock cycles, which is pretty close for most operations.
Hope this information helps.

Yi Y.
Applications Engineer
www.ni.com/support

[Baji]

hai,            thanks for ur reply, pls tell there is any other methods to synchronise two cards with regards  balaji

[Yi Y]

Hi asfdnhsd,

There are many methods to do synchronization, and depending on the application, there's no best way.  Attached image is another method that might work for you.
Same idea, the master portion of the code compiles onto one device and the slave compiles onto the next device.
With this set up, you generate a square wave on the 40MHz onboard clock on the 7831R board.  That output is hard wired to a digital input on each of the boards (make sure the wires are about equal length to reduce offset.

Hope this helps.

P.S. I made a mistake in the screenshot I attached above.  The slave is suppose to be writing to Trigger 1 instead of Trigger 0.

Yi Y.
Applications Engineer
http://www.ni.com/support

[orelb]

Is there no better way of synchronizing two FPGA cards (PCI-7833R)?

Even if you use one to trigger the other, they will still start to drift apart upon execution...