External Clocks for 7811R

[EMax]

I recently purchased a 7811R.  I have a need to synchronize to external clocks (require 3 actually).  How do I configure external clocks for the 7811R in Labview FPGA modules.

[AdnanZ]

Here is a good explanation of this:

Using External Clocks for Synchronous Design (FPGA)

If you have any other questions, post back.

[EMax]

Thank you for your quick reply.  I have reviewed the documentation, and have attempted to implement in the 7811R.  I guess I have a more fundamental question: Does the 7811R support using a digital I/O resource as an external clock?

[mishkin]

Emax,

Are you unable to set one of your DIO lines as your external clock reference  after looking through the link posted above? Are you disabling and enabling your external clocks properly?

[mishkin · Accepted solution]

Emax,

Unfortunately, not all FPGA targets support this functionality. Currently, the R series cards are not able to do this. However, FlexRIO targets support using DIO resources as an external clock, including the following models:7951R, 7952R, 7953R, and 7954R.

Which components are you trying to synchronize in your application and how fast do you need your clock to go? 

[EMax]

Thank you for your comments.  Your information has helped me to realize that I am unable to configure the R-series DIO as an external clock.  My maximum clock frequency is 1.6MHz and I am interfacing to a custom built control system.  Unfotunately, I have a requirement to provide a PCI interface--hence why I selected the 7811R.  So any recommendations would be useful.

-Erick

Message Edited by EMax on 04-01-2009 09:32 AM

Message Edited by EMax on 04-01-2009 09:34 AM

[mishkin]

Erick,

In the realm of National Instruments products, if you need a high speed reconfigurable target (FPGA) that utilizes external clocking, FlexRIO is your only option (all PXI based). If you were willing to forgo the "reconfigurable" factor, you may want to look into some of our PCI high-speed products. 

[M.haefner]

Emax,

you could "simulate" synchronization to your external clock by sampling your signals in a SCTL. I realized a SPI slave receiver that way and could successfully read around 30MBps. The SCTL clock was 160MHz. If you can live with the resulting jitter and delay, that might be a solution for you.

Regards,

Matthias

[weiliem]

i want to read a ram with 8bit data and 8bit address ,clock 512k,do you have any thinks?