Subject: Re: [IBIS] Parameterization in BIRD 75
From: Ross, Bob (bob_ross@mentorg.com)
Date: Thu Sep 19 2002 - 16:36:54 PDT
Lynne, Arpad, Ian and All:
Great point about encryption. I agree with Arpad that often
in "SPICE" the .params are in the file and outside of the
sensitive encrypted regions. In other languages, if the
internal contents are encrypted, then some other documentation
(or model-vendor provided script) is needed to document
what parameters exist.
The names are then available, and the type, and other
information should be available. Otherwise, how would anyone
know of these "secret" parameters and what to enter?
Besides, as Arpad points out, the EDA tool de-encrypts the file
for storage in some internal data structure. The secret
contents are tagged in some manner so that it cannot be
revealed outside of the data structure. However, some
parameters could still be passed outside from internal
data structures such as initial values of parameters to
be passed in - expecially if they were intended to be
used in that manner. So it may possible to pass some internal
parameters outside of the file - such as the default parameter
value for display in a pull-down window interface. However,
there also could be the risk that this is not supported or
should not be supported for security reasons if it is part of
the encrypted data.
Bob Ross
Mentor Graphics
"Muranyi, Arpad" wrote:
>
> Lynne,
>
> I wasn't thinking of my explanation as "not bringing out"
> those parameters. I thought they would be dug out by the
> tool using the list of parameter names in the IBIS model.
>
> However, you raised some interesting points regarding encryption.
> One of my reactions would be that the tool has to decrypt even
> those models in order to simulate with them, so at that level
> the tool would know what is in it, so it could dig the parameters
> out to the user interface.
>
> But, (at least in HSPICE) you don't have to encrypt the entire
> model. You can put markers in there for the encryptor to tell
> it where to start and where to end with the encryption. So
> you can make an encrypted model who's .subckt definition line
> and all the parameters are readable, and the rest is garbled.
> I hope other encryptions can do it similarly.
>
> Arpad
> ===============================================================
>
> -----Original Message-----
> From: Lynne Green [mailto:lgreen@cadence.com]
> Sent: Thursday, September 19, 2002 2:48 PM
> To: Dodd, Ian; Muranyi, Arpad; ibis@eda.org
> Subject: RE: [IBIS] Parameterization in BIRD 75
>
> 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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