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virtex-II DCM phase shift problems

Hi all, Right now I'm developing a board using virtex-II FPGA, and want to implement a function using the DCM to offer variable(dynamic) phase shifting. I use Xilinx ISE 8.2i, and ModelSim SE for development. As I setup the IP cores for DCM, everything looks fine in the PRP simulation, except that the PSDONE signal never goes high, which means everytime I trigger the PSEN signal to high (for exactly one period, as said in the User Guide), the DCM just doesn't take any action. I just wonder what is other things that I still need to do. If anybody who can address my problem, Thanks!~

Reply to
jack lee
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I have the same problem using my spartan3. Have you solve your proble yet?

thanks

Reply to
cutemonster

Something I saw in my own design: the state machine I was using to control the DCM in my Spartan-3E issued a PSEN before the DCM was ready. Since the state machine was waiting for a PSEN that would never come, my initial reaction was that I never received the PSDONE.

By adding an explicit timeout for the PSDONE to reissue a PSEN as a workaround in my initial code, I was able to issue a first PSEN as seen by the DCM.

Only with this timeout in place did I find that sometimes - making 10s of thousands of adjustments - the time from PSEN to PSDONE would exceed even the 5x timeout period I had designed for on very rare occasions.

If you design a state machine to deal with a timeout, I'd suggest disabling the timeout after the first PSDONE is detected. If you're getting an error because you find yourself waiting too long, wait longer. If you're in this latter camp, it might be helpful to record a histogram of how many clock cycles it takes between PSEN and PSDONE. For your specific input jitter environment, you may get results that deviate from the published maximums.

- John_H

Reply to
John_H

problem

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I checked lock pin and it's locked. So, it should be ready for phas alignment. I don't know why I still couldn't get it to work. How do yo do with your reset sequence? If possible, can I take a look at your cod to see what I missed?

thanks a lot,

Reply to
cutemonster

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