It turns out I did not have the feedback signal connected. So it all works
fine now.

Thanks

Jon

maxascent wrote:
> I have a DDR design from Xilinx MIG and the lock signal never moves from
> '0'. So I have just created my own design with just a DCM and the lock
> signal still is '0'. I cant see that I am doing anything particularly
> wrong?
>
> Cheers
>
> Jon

Are you resetting the DCM (after at least 16 clocks) ?
is your input clock at least 25 MHz?
did you set the resolution of the simulator at 1ps?

Francesco

I have a DDR design from Xilinx MIG and the lock signal never moves from
'0'. So I have just created my own design with just a DCM and the lock
signal still is '0'. I cant see that I am doing anything particularly
wrong?

Cheers

Jon

I would be very careful of using the "locked" signal in any Spartan-3 based 
design as it does not always behave in the way that people assume.


John Adair
Enterpoint Ltd. - Home of Broaddown2. The Ultimate Spartan-3 Development 
Board.
http://www.enterpoint.co.uk


"maxascent" <maxascent@yahoo.co.uk> wrote in message 
news:sMmdnUj9krw4IYvZRVn_vA@giganews.com...
> If am running a simulation in modelsim an there is a DCM block with a
> locked signal. Now because correct me if I am wrong but I would need to
> stimulate the locked signal myself because the DCM will not set it as this
> is just a simulation and the DCM is a piece of hardware. Hope that makes
> sense?
>
> Thanks
>
> Jon 

maxascent wrote:
> If am running a simulation in modelsim an there is a DCM block with a
> locked signal. Now because correct me if I am wrong but I would need to
> stimulate the locked signal myself because the DCM will not set it as this
> is just a simulation and the DCM is a piece of hardware. Hope that makes
> sense?

The DCM model does generate the locked signal. 

Cheers,
Jon

If am running a simulation in modelsim an there is a DCM block with a
locked signal. Now because correct me if I am wrong but I would need to
stimulate the locked signal myself because the DCM will not set it as this
is just a simulation and the DCM is a piece of hardware. Hope that makes
sense?

Thanks

Jon