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Simulators >> AMS Simulators >> Virtuoso AMS : Values not seen in Waveforms
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Message started by deepak srinivasan on Feb 26^th, 2012, 10:15pm

Title: Virtuoso AMS : Values not seen in Waveforms
Post by deepak srinivasan on Feb 26^th, 2012, 10:15pm

Hi

I tried to import a Not Gate verilog in to Virtuoso (IC 6.1.3.1) through the verilog in form
the not gate code :

module notgate(b,a);
output b;
input a;
assign b =~a;
endmoudule

after i imported it i created a schematic cell view with the input of not gate as a pulse voltage source (voltage varying from 0 to 1.8V with rise time 1ns, fall time 1ns, pulse width as 5ns and time perion as 10ns)
and the output was attached to an output pin
later i created its config view with AMS template
in the ADE L window i selected AMS simulator, gpdk.scs as model library ans spectre as solver
when i do run the ADE i get an output waveform that has no values in its y axis
my specctre version is 78.2.0
what could be the possible source of error
if i had missed any piece of information kindly point it out
regards
deepak

Title: Re: Virtuoso AMS : Values not seen in Waveforms
Post by boe on Feb 27^th, 2012, 6:46am

Hi deepak srinivasan,
Spectre Version 78? Never heard of that one...
Which IUS/INCISIV version do you use? I assume you run a transient simulation? Did you save all signals you want to see? Which CMs (connect modules) do you use? Do you use detailed discipline resolution mode?

Just a few questions that come to mind quickly...
- B O E

Title: Re: Virtuoso AMS : Values not seen in Waveforms
Post by deepak srinivasan on Feb 27^th, 2012, 7:12am

Hi

I am sorry if posted anything wrong
I am new to Cadence tools
The version of spectre i posted is what i got by typing "which spectre"
i guess i had copied it correctly
at the moment i away from college which has these Cadence tools
will post about the versions of INCISIV once I go there

Yes I am running a Transient simulation.
And in the output i could see the waveform and it behaves as expected (i.e. high when input is low and low when input is high) but only that the y-values are not there

I am using 5V connect modules (though i tried with 1.8V and 3V modules as well but there was no difference)

i am including only "gpdk.scs" as Model Library
i tried to include nmos1.scs and pmos1.scs it shows error
is there anything else i should add

regards
deepak

Title: Re: Virtuoso AMS : Values not seen in Waveforms
Post by boe on Feb 27^th, 2012, 9:33am

Hi deepak srinivasan,
to get the version numbers you should run spectre -V / ncsim -version.

Quote:

... but only that the y-values are not there

you mean on the y-axis? That is normal for digital signals (assuming that is what you look at).
- B O E

Title: Re: Virtuoso AMS : Values not seen in Waveforms
Post by boe on Feb 27^th, 2012, 9:38am

Hi,
one more thing:

deepak srinivasan wrote on Feb 27^th, 2012, 7:12am:

I am using 5V connect modules (though i tried with 1.8V and 3V modules as well but there was no difference)

You seem to work on a 1.8V design (according to your initial post), so you should use 1.8V CMs as well.

- B O E

Title: Re: Virtuoso AMS : Values not seen in Waveforms
Post by Forum Administrator on Feb 27^th, 2012, 10:05am

CMs is short for Connect Modules.

-Ken

Title: Re: Virtuoso AMS : Values not seen in Waveforms
Post by deepak srinivasan on Feb 27^th, 2012, 5:20pm

You seem to work on a 1.8V design (according to your initial post), so you should use 1.8V CMs as well.///

yes i tried with 1.8 V CM
and i changed the input to 5V and tried with 5V CM as well
but there is no difference in the output

Title: Re: Virtuoso AMS : Values not seen in Waveforms
Post by deepak srinivasan on Feb 27^th, 2012, 5:22pm

you mean on the y-axis? That is normal for digital signals (assuming that is what you look at).
///

i am trying to find the propagation delay and power consumed similar to what is given in the Cadence AMS tutorial for which i would be needing voltage values on y axis.

Title: Re: Virtuoso AMS : Values not seen in Waveforms
Post by boe on Feb 28^th, 2012, 3:23am

Deepak srinivasan,
the digital model you gave in the initial post of this thread has neither power consumption nor delay. If you want to measure delay and power you need a transistor-level model (implementation).

- B O E

Title: Re: Virtuoso AMS : Values not seen in Waveforms
Post by deepak srinivasan on Feb 28^th, 2012, 3:38am

Hi

Thanks
But in the Tutorials they simulated a SAR ADC using Verilog Coding and found out its delay as well as power consumption

I am writing codes for various types of multipliers for which i need to find the delay and power consumption
i may not be able to draw a transistor level schematic as they have a large no of transistors

Any advice on this would be helpful

Title: Re: Virtuoso AMS : Values not seen in Waveforms
Post by boe on Feb 28^th, 2012, 6:31am

deepak srinivasan wrote on Feb 28^th, 2012, 3:38am:

...
But in the Tutorials they simulated a SAR ADC using Verilog Coding and found out its delay as well as power consumption

I am writing codes for various types of multipliers for which i need to find the delay and power consumption
i may not be able to draw a transistor level schematic as they have a large no of transistors

Yes, there are ways to estimate and model delay and power consumption of digital (gate-level) blocks/cells based on characterization of individual gates on transistor level, e.g. timing analysis (for delay).
- B O E

Title: Re: Virtuoso AMS : Values not seen in Waveforms
Post by deepak srinivasan on Feb 28^th, 2012, 8:03am

Hi

Can you give me any link that describes how to do that.
Thanks in advance

Deepak

Title: Re: Virtuoso AMS : Values not seen in Waveforms
Post by deepak srinivasan on Mar 1^st, 2012, 9:09am

Hi

Can anyone please help me by providing link to a tutorial on finding delays for digital blocks
i am unable to find it

regards
deepak

Title: Re: Virtuoso AMS : Values not seen in Waveforms
Post by boe on Mar 6^th, 2012, 7:26am

Deepak srinivasan,
this is not a V-AMS question. Try synthesis tools or static timing analysis tools (e.g. Cadence ETS, Synopsys Primetime) and their tutorials.
- B O E