RE: [IBIS] Submodel clamping curves

Danny:

The way to understand [Submodel]s is to consider them as

independently functioning models whose outputs are connected

to the common IO node of the top-level model. The top-level

model and all submodels under it are simulated simultaneously.

Their combined (and sometimes time-varying) impedances

are seen by the top-level model and all submodels due to the

common connection.

The Submodel_types including Bus_hold and some extended operations

of the Dynamic_clamp have active submodel simulations even if the

top-level model is in Input model (Non-Driving mode).

So treat the submodel as an independent model, and not as

a model whose I-V tables are added to the top-level model.

Bob

From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Danny
Wherrett
Sent: Tuesday, March 22, 2011 6:53 PM
To: ibis@eda.org
Subject: [IBIS] Submodel clamping curves

Hi All,

I am working on updating support in a simulation tool for certain ibis
keywords.

Two of these are the [Add Submodel] and [Submodel] constructs.

Currently I am trying to determine how I-V curves defined in the submodel
should be combined with those of the parent model to obtain the overal
characteristics. It seems to me that the curves should be added, but I
wanted to gain clarification on this.

For example:
The [Model] defines a [GND Clamp] curve.
The [Add Submodel] mode is set to non-driving.
The [Submodel] defines a [GND Clamp] curve also.

When the model is driving, just the original GND clamp curve will be used,
since the submodel will not come into play due to the non-driving mode.

When the model is recieving, then the GND Clamp curves will be added to
obtain the full GND clamping effect including the submodel.

Is my understanding here correct?

And will this be the same for the other keywords supported by the submodel
i.e. [Pullup], [pulldown], [ramp], [power clamp] etc. ?

Regards,
Danny Wherrett

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