DCM start up

I've got a DCM as part of a 4 byte Aurora implementation on a VII Pro. Sometimes after JTAG configuration the DCM just won't lock (hence the ChannelUp never happens either). Once it's decided not to work, doing the reconfiguration again or resetting has no effect. If I then configure with an old version of code (also with a power cycle) it works OK with old and new code. Are there any tricks I should know about here either in the VHDL or settings in the tools that anyone can tell me about please as I really need to get around this problem?

TIA,

Rog.

Reply to
Roger
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Roger,

What is the status of the DCM is this condition (the status byte)?

It may be that the CLKFB signal isn't right while the DCM attempts to lock, and it either can't lock (taps on delay lines overflow or underflow), or it locks in the wrong place.

Try resetting the DCM after a delay to allow oscillators and all circuitry to stabalize.

Austin

Roger wrote:

Reply to
Austin

May not be related to the DCM problem, but starting the PPC from JTAG in a V2Pro was also problematic (random failure, probability > 50%) unless the "Pulse Prog" option was ticked in IMPACT.

My webcase didn't get a clear explanation from Xilinx, so I suggest these two startup problems MAY be related, and (if you're using Impact) it's a quick and easy change to try. (If you're accessing JTAG by some other tool, there must be some way to pulse the PROG pin). I'd be interested to hear if this clears the problem.

- Brian

Reply to
Brian Drummond

Do you have a post-configuration startup reset for the DCM's ?

see Answer Record 11778: "Virtex/-E/-II/-II Pro, Spartan-II/-IIE/-3 - Device configures correctly after PROG is pulsed, but DLL/DCM/DCI does not function correctly when reconfigured

Also note, when configuring a device from JTAG that also has an external configuration PROM, it is best to set the mode pins to JTAG, and/or erase the PROM, to avoid weird configuration problems. (Answer Records 9013, 16829, 22255)

Brian

Reply to
Brian Davis

Just read your replies. Lots of good stuff to try. I'll do some experiments.

Thanks very much for taking the time to reply.

Merry Christmas

Rog.

Reply to
Roger

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