DCM ISE6.2.3 sim problem

[wolfgang]

hey guys!

i trie to simulate a dcm design with modelsim, but the dcm doesn't start. i
tried to reset the dcm after applying clkin, it seems, that the dcm is
working, but clkfx is only a amount of spikes instead of a 50:50 clock but
at the right frequency. clkin is a 60%:40% clock with 33 MHz.

anyone out there with the same problem?

thx

wolfgang

 

[jakab tanko]

Do you have your modelsim resolution set to ps?
"wolfgang" <wolfgang.hofmann@arcs.ac.at> wrote in message
news:cc14ut$on9$1@newsreader1.utanet.at...

hey guys!

i trie to simulate a dcm design with modelsim, but the dcm doesn't start.
i
tried to reset the dcm after applying clkin, it seems, that the dcm is
working, but clkfx is only a amount of spikes instead of a 50:50 clock but
at the right frequency. clkin is a 60%:40% clock with 33 MHz.

anyone out there with the same problem?

thx

wolfgang

 

[Brian Philofsky]

As mentioned, you need your simulator set to ps resolution. Anything
coarser can make the model not operate properly. Newer versions of the
model warn against this but older ones did not. Also, if you reset the
DCM, you must hold the reset for at least 3 full clock cycles. This is
a hardware requirement and newer versions of the model again warn you of
this. Also check to see if LOCK has gone high. It can take several ns
before the DCM LOCKs and before that time, some runt pulses can be seen
but after you have achieved LOCK, the DCM is supposed to be operating
properly. Also, ensure you have all of the attributes properly set for
the DCM as they have an obvious effect on the operation of the model.


-- Brian


jakab tanko wrote:

Do you have your modelsim resolution set to ps?
"wolfgang" <wolfgang.hofmann@arcs.ac.at> wrote in message
news:cc14ut$on9$1@newsreader1.utanet.at...

hey guys!

i trie to simulate a dcm design with modelsim, but the dcm doesn't start.

i

tried to reset the dcm after applying clkin, it seems, that the dcm is
working, but clkfx is only a amount of spikes instead of a 50:50 clock but
at the right frequency. clkin is a 60%:40% clock with 33 MHz.

anyone out there with the same problem?

thx

wolfgang