Subject: RE: [IBIS] Parameterization in BIRD 75
From: Lynne Green (lgreen@cadence.com)
Date: Thu Sep 19 2002 - 14:47:45 PDT
Hi, Arpad,
Often, designers want to do "what-if" analysis. It is easier
for the EDA tools to support this if parameters (ones the
user is allowed to vary) are brought out to the top level.
As you point out, constant parameters (ones users are
not allowed to change) should not be brought out.
Also, when the external model file is encrypted, the EDA
tool will not have access to the parameter names or values.
A number of language implementations (not just HSPICE)
support encryption. Adding parameters at the top level
increases the flexibility of the BIRD.
Best regards,
Lynne
-----Original Message-----
From: Dodd, Ian [mailto:ian_dodd@mentorg.com]
Sent: Thursday, September 19, 2002 1:28 PM
To: 'Muranyi, Arpad'; ibis@eda.org
Subject: RE: [IBIS] Parameterization in BIRD 75
Arpad,
My thought was that we might want to have the SI tool GUI read all the
information from the standard part of the External Model, rather than
having to look for it in the referenced external models. The latter
requires that the GUI understand the external model syntax.
I agree with you that in some cases the information would be redundant,
but it seems to me to be a cleaner way to implement the general case.
To me this is not a major issue - so if the majority thinks this is
un-necessary, I am very willing to go along with the majority view.
Ian
-----Original Message-----
From: Muranyi, Arpad [mailto:arpad.muranyi@intel.com]
Sent: Thursday, September 19, 2002 1:31 PM
To: ibis@server.eda.org
Subject: RE: [IBIS] Parameterization in BIRD 75
Ian,
If I am not mistaken, what you are suggesting can be done the way the
BIRD is written now. I will re read it again to make sure, but here is
the way I understand it now:
The IBIS model will list the names of the parameters only. The
parameter is defined inside the ***-AMS model with their default values,
and type definitions, etc... The IBIS model simply tells
the tool what the parameters are that is should search for in the
[External Model] (or [External Circuit]). The tool's GUI then should
pick up the parameters and their associated values, types, etc... from
the external modes and present it to the user so they can change it, or
set up parametric sweeps etc...
I don't think it is necessary in the IBIS model to spell out those
details you are listing, because they are already spelled out in the
referenced external models. That would be redundant, and would not
provide any added benefit, as I see it now.
Do you have a reason that would make my thinking incorrect, or invalid?
I just want to re read the BIRD, to make sure that it says what I think
it should say.
Arpad
=====================================================================
-----Original Message-----
From: Dodd, Ian [mailto:ian_dodd@mentorg.com]
Sent: Thursday, September 19, 2002 11:38 AM
To: ibis@eda.org; Ross, Bob
Subject: RE: [IBIS] Parameterization in BIRD 75
To All,
Sorry for the delay in following up my comments in the Open Forum.
I'm very keen to have a Parameterization feature for external models.
If we add this feature, I would expect simulation tools
would provide a mechanism for the user to enter values for the
parameters
in an interactive fashion.
To do this the following information would be necessary:
parameter name
parameter value
In addition it would be useful to have the following additional
information
parameter type
default value
value validation range
units
Bob's proposal of quoting parameter values that textual, implicitly
gives the parameter type as numeric or textual.
This does not distinguish floating point from integer values. That
additional information would be useful for validating the value in a
form, but I personally think we could live without it.
I think we could also live without the validation range.
I think we should require a default value for each parameter
and allow it to be followed by an optional units string as per other
IBIS fields. If the units are present, a form prompting for parameter
values should be free to display the appropriate units.
Based upon my comments, I would suggest we could amend the parameter
section from
Parameters r1 l1
Parameters r2 l2 temp
to
Parameters r1 = 15ohms l1 = 10mH corner = "min process" Parameters r2
= 25 l2 = 22m temp = 75degF
or better still
Parameter r1 = 15ohms
Parameter l1 = 10mH
Parameter corner = "min process"
Parameter r2 = 25
Parameter l2 = 22m
Parameter temp = 75degF
I think the second form is better because it would allow us to more
easily
add additional information to each parameter (such as ranges) in a
future BIRD.
We might also achieve this by requiring explicit (comma?) delimiters
between entries in the first form.
Ian Dodd
Mentor Graphics Inc
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