Subject: Model name question

From: "Muranyi, Arpad" <[email-masked]>
Date: Thu, 12 Jul 2001 14:56:11 -0700

All,

I would like to find out whether there is a need to include the
component name as part of the buffer names for the [Model]
keyword in an IBIS file.  The reasoning goes like this:

If there are two different IBIS files with buffer names inside
them which are the same (while the electrical characteristics
of the models are different) and these two models are used in
the same simulation, could the tool lose track of which one is
which?

Do tools make these names unique for simulations to prevent
this from happening so that me as a model maker wouldn't have
to worry about this?

Thanks,

Arpad
=================================================================

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From: Scott McMorrow <[email-masked]>
Date: Thu, 12 Jul 2001 15:28:03 -0700

Arpad,

I believe many simulator vendors already identify models
internally by the following tuple:

(component_name, model_name)

I would recommend formalizing this in future IBIS specifications.
We need not specify the exact format of the naming convention,
but we do need to clarify that a model should be identified by
component_name and model_name, since model_names are
not unique.

If we were all real sticklers, we would require tools to identify
a model by the following tuple:

(component_name, model_name, revision)

Many a time I have been bit by multiple revisions of models laying
around ... especially with automatic path searches of model directories,
where the last model loaded is the one that is used.

regards,

scott

--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com

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From: Mike LaBonte <[email-masked]>
Date: Thu, 12 Jul 2001 18:55:49 -0400

A simulator that works directly from IBIS files is able to employ
scoping, so that buffer models are only seen by components in the
same file. Simulators that translate the IBIS files and import
the data into libraries of some other format may lose that same-file
relationship, unless other techniques are employed. One technique
is to concatenate the IBIS file name to all buffer model names.

So I think the answer to Arpad's question is "yes".

Mike

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From: Abdulrahman Rafiq <[email-masked]>
Date: Thu, 12 Jul 2001 16:07:10 -0700

Arpad,

Do you mind trying to rephrase your question ?

--
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| Abdulrahman A. Rafiq (AKA Abbey)   |         ---           ---         |
| Hardware Engineer                  |       -------        ------       |
| ISBU, Cisco Systems, Inc.          |     -----------    ----------     |
--------------------------------------   ------------------------------  |
-------------------------------------------------------------------------

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From: "Matthew Flora" <[email-masked]>
Date: Thu, 12 Jul 2001 16:17:09 -0700

Scott, Arpad,

May I suggest that you are headed toward a slippery slope.  One common name
conflict with models that the tuples mentioned do not eliminate is second
source parts from multiple manufacturers.  They might have started with the
same model and tweaked it for their process.  If you try to come up with a
scheme where a single name includes every possible identifying mark, then
you'll end up with a ridiculously long name.

I suggest leaving it to the tools to keep track of which model they are
dealing with.  It ain't difficult.  Software has had to do this for a long
time.  It's not new.  It's not rocket science.

Cheers,
Matthew Flora

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From: Scott McMorrow <[email-masked]>
Date: Thu, 12 Jul 2001 17:33:46 -0700

Matthew,

I believe you misunderstood me.

> component_name and model_name, since model_names are

I do not suggest any particular naming and/or scoping convention
for IBIS models.  I do suggest that it be required that some sort
of convention is used and defined by each vendor, so that
name space and revision problems are eliminated.  I suggest that
IBIS specifications require that models be tracked in a way that
naming conficts cannot occur and revision control can be facilitated.

You have just suggested a further clarification to the model naming
problem (i.e. manufacturer).  I believe the following will uniquely
identify an IBIS model in most all cases:
(manufacturer, component_name, model_name, revision)

My experience is that what is not specified is what breaks designs.
I would much rather err on the specification side after 22  years of
design work.  I've used way too many components and software which
use assumptions which are ill-defined, are unpublished to protect the
guility, or are in opposition to common sense.

It's time to dispel the assumption that component designers and
software vendors will do the right thing.

regards,

scott

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From: Al Davis <[email-masked]>
Date: Fri, 13 Jul 2001 10:04:45 -0700

> (component_name, model_name)

Almost.

It is:
(file_name, model_name)

or
(file_name, component_name, pin_name)

A file can contain more than one [Component] and more than one 
[Model].  In this case, the [Model]'s are available to all 
[Component]'s in that file.  All of these are placed in the file's 
global scope, which translates at best to file scope when there is 
more than one file.

The proposed connector spec introduces another scoping mechanism 
[Cn_Model_Family] (or something like that) which may be worth 
adopting in general.  Still, to avoid confusion the concept of file 
scope must be continued.

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From: Lynne Green <[email-masked]>
Date: Mon, 16 Jul 2001 10:45:31 -0700

Hi, Scott and Arpad,

I like the idea of formalizing this.  At the
same time, should we consider allowing
more than 20 characters is a buffer name?

Cadence uses COMP + MODEL now, and
also makes the combination unique within
a simulation (default setting).

- Lynne

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From: Scott McMorrow <[email-masked]>
Date: Mon, 16 Jul 2001 11:14:28 -0700

Lynne,

My suggestion is to formalize the concept that a unique model name is
described by the following:

manufacturer.component.model.revision.

... and that  simulator vendors should attempt to manage models
down to this level of detail.  However, understanding that no vendor
currently is capable of doing this, that this is desired for future designs
with IBIS-X. It should be recommended that vendors document the current
method for model management and acknowledge whatever current
flaws and name space colisions which can occur.  (this is not to point
fingers, but rather so that users can correctly accomodate the various
tool "qwirks" and guarantee valid simulations.

An example "qwirk" might occur when multiple files are loaded into
a simulation tool, both of which have the same component name.
This can happen easily when multiple revisions of an IBIS model exist,
or when there are multiple vendors for the same component.

regards,

scott

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From: Al Davis <[email-masked]>
Date: Mon, 16 Jul 2001 13:41:44 -0700

On Monday 16 July 2001 11:14 am, Scott McMorrow wrote:
> Lynne,
>
> My suggestion is to formalize the concept that a unique model name
> is described by the following:
>

That doesn't work.  Model is not in Component scope.  Model and 
Component are at the same level as far as scoping is concerned.

You can have a file ...

[Component]
[Component]
[Component]
[Model]
[Model]
[Component]

etc...

All models are available to all components in that file.

The only scoping we have is by file.

Moving forward, it may make sense to introduce a [Namespace] to deal 
with these scoping issues, but I don't think this will solve the 
problem either.

Should IBIS-X offer nested [Define]s ??

al.

---

From: "Todd Westerhoff" <[email-masked]>
Date: Tue, 17 Jul 2001 08:31:03 -0400

You know, you could just put one component per file.  That's what I do, for
exactly the reason you mention.

Todd.

Todd Westerhoff
SI Engineer
Hammerhead Networks
5 Federal Street
Billerica, MA  01821
[email-masked]
ph: 978-671-5084

-----Original Message-----
From: Al Davis [mailto:[email-masked]]
Sent: Monday, July 16, 2001 4:42 PM
To: Scott McMorrow; Lynne Green
Cc: Muranyi, Arpad; [email-masked]'
Subject: Re: Model name question

You can have a file ...

[Component]
[Component]
[Component]
[Model]
[Model]
[Component]

etc...

al.

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From: Mike LaBonte <[email-masked]>
Date: Tue, 17 Jul 2001 10:50:00 -0400

Adding more complexity to the name scoping features in IBIS-X
may not help. The file level scoping in IBIS works today for
tools that work directly from IBIS files, building a simulation
model in memory and discarding it when the program exits. It is
easy for these to observe the scoping rules, and they may have
little trouble adapting to new scoping.

It is the tools that save the simulation models in proprietary
libraries that need special measures to preserve the
model-to-component linkage, because short "nicknames" for
models become pretty non-unique when they are all thrown into
one big library. An IBIS-X file with flexible scoping may
present even more difficulty for these tools, which usually
encode enough information into the stored model names to keep
the linkage straight later. More complex scoping could lead to
less readable model names.

It would be nice, of course, if no translation were needed.
IBIS-X may be flexible enough to eliminate the need for tools
to have their own proprietary formats, but I wouldn't count
on that happening for some time. The proprietary libraries
can take on a life of their own.

Mike LaBonte