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Re: [Help-gnucap] Time step control

From: a r
Subject: Re: [Help-gnucap] Time step control
Date: Mon, 3 Dec 2007 18:51:45 +0000

Now, how to use the models?

I have attached the and got a message:

M: already installed, replacing
stashing as M:0

When I use MOSIS models (level=49) directly I get error:

Mp.xi1: model cmosp is not a bsim330,bsim3

When I change level from 49 to 8 the simulation _works_ but I get some

^ ? bad parameter, ignored

and then bunch of warnings:

Warning: This model is BSIM3v3.3.0; you specified a wrong version number.
Warning: Pd = 0 is less than W.
Warning: Ps = 0 is less than W.
initial step rejected:Mp.xi1
new=1.87716e-12  old=1e-11  required=5e-12
storage element step control error:Mp.xi1 6.11037e-17
using Euler, disabling time step control


On Dec 3, 2007 5:01 PM, al davis <address@hidden> wrote:
> On Monday 03 December 2007, a r wrote:
> > Still I have a feeling that playing with options is a hack.
> > Why gnucap does not recognize that the state of the circuit
> > (bsim3 transistors) changes and it should simulate the
> > transition more precisely?
> You might consider to try the exact Spice model.  All Berkeley
> variants of the BSIM3 model are in the models-bsim package.  If
> you are not sure which to use, the most recent "BSIM3v330" is
> probably the best choice.
> To use the Berkeley model, build that library,
> ("make" should build the whole tree)
> then "attach -------".  You can do the attach as "-a" on the
> command line.
> There could be a bug in the ".model" port of the model.  I do
> know that modelgen has the "hidden state" bug that people
> complain about in Spectre.  I also know that the capacitance
> portion of the port (d_mos8.model) has not been tested very
> well.
> Now that gnucap can use the exact Spice model, the ".model"
> files that contain ported model code will be phased out.  In
> the future, a new version of modelgen will accept Verilog-A as
> the source language.  My effort has been directed toward that,
> rather than fixes to code that will be removed.
> I am not aware of any simulator that gets the step control
> correct over a region change.  I know that Spice does not, that
> anything based on "ADMS" does not, and that anything that uses
> the Berkeley models as they come does not.  Gnucap has the
> mechanism for doing it, but the model needs to call it.  Spice
> doesn't even have the mechanism.
> In the future, the "attach" command will be able to manage the
> compiling of a plugin, so you will be able to attach a source
> file or directory without worrying about the compiling details.
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