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Comp.Arch.FPGA | Spartan 3 DCM

There are 6 messages in this thread.

You are currently looking at messages 0 to 6.

Spartan 3 DCM - maxascent - 2006-03-14 07:52:00

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

Thanks

Jon



Re: Spartan 3 DCM - Jon Beniston - 2006-03-14 08:00:00

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

Re: Spartan 3 DCM - John Adair - 2006-03-14 08:48:00

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" <m...@yahoo.co.uk> wrote in message 
news:s...@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

Re: Spartan 3 DCM - maxascent - 2006-03-14 09:56:00

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 locksignal still is '0'. I cant see that I am doing anything particularlywrong?

Cheers

Jon

Re: Spartan 3 DCM - Francesco - 2006-03-15 04:03:00

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
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Re: Spartan 3 DCM - maxascent - 2006-03-15 05:48:00

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

Thanks

Jon
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