[SI-LIST] Re: Transient sim in specific time points
- From: "Lynne D. Green" <lgreen22@xxxxxxxxxxxxxx>
- To: Ben <ben01010@xxxxxxxxx>
- Date: Thu, 25 Mar 2010 23:08:13 -0700
Hi, Ben,
Your problem might be bigger than you think.
* If I remember correctly, HSPICE (and other flavors) solve at
"internal" timepoints, for simulation efficiency and accuracy. The
.TRAN print output is then interpolated based on those internal
timepoint solutions.
* These internal timepoints are not required to include any of the
"breakpoints" of your input source (except time=0).
* The .OPTIONS can be used to limit the step between internal
timepoints. The convergence tolerance options also have an effect on
timepoint selection, plus some of the other options. Note that
overconstraining tolerances can make the simulation run longer and
perhaps make the simulation fail to converge.
* The output plot (*.tr0) probably contains the complete internal
timepoint results.
* One possible solution: take the *.tr0 file, and write a script to
extract the timepoints of interest. Of course, there will be some
tolerance needed in picking the timepoints, since they probably do not
all fall exactly on the desired times. One could even implement
interpolation if needed.
* Another possible solution: make the .TRAN print time interval small;
there might be a print step size that will hit all of your desired times
exactly (plus a lot of others), but the file might still be smaller that
the *.tr0 file. Again, one could write a script to extract the
timepoints of interest from the *.lis (*.out) file. The advantage here
is a smaller output file (but with more overhead info). On the other
hand, scripting might be easier with the *.tr0 file, since there is less
text to ignore.
Best of luck.
Lynne
"IBIS training when you need it, where you need it."
Dr. Lynne Green
Green Streak Programs
http://www.greenstreakprograms.com
425-788-0412
lgreen22@xxxxxxxxxxxxxx
Ben wrote:
> Hi all
> I need to perform a transient simulation but i need the results at specific
> time instants.
>
> I know that, regardless of the internal time steps Hspice internally may
> take for numerical integration user can get the simulation results at
> specific time instants (eg. equally spaced time points) defined by .tran
> command.
>
> In my case I have a list of time points (say 1000 points) at which I need
> the transient response. These time points are not equally separated.
> According to Hspice-command-ref I guess the following statement may have a
> clue for the solution
>
> .TRAN data = dataname
> This example is a data-driven time sweep. It uses a data file
> as the sweep input. If the parameters in the data statement
> are controlling sources, then a piecewise linear specification
> must reference them.
>
>
> But I am not sure whether it can give me what i am looking for or how I can
> define "data-file" indicated as data = dataname.
> What is the required file structure for the data-file,
>
>
> I would appreciate any input in this regard.
>
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