RE: [IBIS] Submodel clamping curves

Bob,

I think Danny was really trying to get help on which I-V table

is in effect in which mode...

Danny,

Bob is correct, the Submodel can be treated as an independent

[Model], but its presence is determined by the mode:

Driving - only in the circuit when the buffer is a driver

Non-Driving - only in the circuit when the buffer is receiver

All - it is in the circuit at all time.

But the usual rules about the I-V curves apply on top of that.

Clamps are always there, provided that the above conditions

allow it to be there, Pullup and/or pulldown are only there

when driving high or low, respectively, provided that the

above conditions allow them to be there.

I hope this answers your questions.

Arpad

===============================================================

From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Bob
Ross
Sent: Tuesday, March 22, 2011 9:48 PM
To: 'Danny Wherrett'; ibis@eda.org
Subject: 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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