Comments on IBIS BIRD64.3 - Alternate Package Models

To All:

I had some comments for Mike LaBonte, but we decided to carry on the
discussion on the IBIS reflector for more input.

1. The content of [Alternate Package Models] .. [End Alternate Package
Models] are all the ADDITIONAL package models. The default package
model is still called by the [Package Model] keyword.

  (a) What happens if [Package Model] is not defined?

      Error?
      Different default (e.g., the [Pin] or [Package] entries?
      The first entry of [Alternate Package Models] is the default?

  (b) Can the [Package Model] selection be listed in the [Alternate Package
Models]
      list? (This might occur when editing a different default.)

      Yes
      No, Error
      Yes, Warning

2. My preference would be to change the keyword to [Package Model Options] or
something else (but changed from [Package Model Selector] to avoid confusion
with some different rules for [Model Selector] and make it function independent
from any other keyword. It would have the highest priority. Similar to [Model
Selector]
the default would always be the first entry in the list.

(a) Would this structure be better for EDA tools that might want to create a GUI
(the list is in one keyword, not two keyword)?

(a) Similarly, is this better for scripting (the language may reference the
contents
of one keyword, not two keywords?

3. Are there any better names than [Alternate Package Model]?

Bob
     

Bob Ross wrote:
>
> To All:
>
> In response to some comments at the October 27, 2000 IBIS Meeting
> BIRD64.3 is Issued. The title has been changed from Package
> Model Selector to Alternate Package Models.
>
> Discussion on BIRD64.3 can be done on the IBIS reflector.
>
> Bob Ross
> Mentor Graphics
>
> *******************************************************************************
> *******************************************************************************
>
> BIRD ID#: 64.3
> ISSUE TITLE: Alternate Package Models
> REQUESTER: Arpad Muranyi, Intel; Mike LaBonte, Cadence
> DATE SUBMITTED: 10-25-99, 11-19-99, 10-8-2000, 11-1-2000
> DATE ACCEPTED BY IBIS OPEN FORUM: Pending
>
> ******************************************************************************
> ******************************************************************************
>
> STATEMENT OF THE ISSUE:
>
> The current IBIS specification (3.2) does not provide a selection mechanism
> for multiple package models. This may be necessary when a certain die is
> shipped in various package styles, or when the corner cases of the package
> are described with different package models.
>
> This BIRD is written to provide an easy solution to this deficiency. This
> feature will allow simulator tools to implement a user friendly package
> model selection interface and/or better automation for batch and sweep
> simulations.
>
> ******************************************************************************
>
> STATEMENT OF THE RESOLVED SPECIFICATIONS:
>
> A new keyword shall be introduced in the IBIS specification to provide a user
> friendly package model selection mechanism for components which use multiple
> package models. The proposed keyword [Alternate Package Models] shall contain
> a list of package model names that the simulator can pick from, in addition to
> the default package model name given by the [Package Model] keyword. The
> package model names listed under the [Alternate Package Models] must follow
> the rules of the package model names associated with the [Package Model]
> keyword.
>
> To help the user of the simulator tool to make an intelligent choice, it is
> highly recommended that a description be placed to the right of each package
> model name in the list as a comment.
>
> |=============================================================================
> | Keyword: [Alternate Package Models] [End Alternate Package Models]
> | Required: No.
> | Description: Used to select a package model from a list of package models.
> | Sub-Params: None.
> | Usage Rules: The [Alternate Package Models] keyword can be used in addition
> | to the [Package Model] keyword. [Alternate Package Models]
> | may be used only for components that use the [Package Model]
> | keyword.
> |
> | Each [Alternate Package Models] keyword specifies a set of
> | alternate package model names for only one component, which
> | is given by the previous [Component] keyword. The [Alternate
> | Package Models] keyword may not appear before the first
> | [Component] keyword in an IBIS file. The [Alternate Package
> | Models] keyword, when used, must follow the [Package Model]
> | keyword within the same [Component] section, and must be
> | followed by an [End Alternate Package Models] keyword..
> |
> | All alternate package model names must appear below the
> | [Alternate Package Models] keyword, and above the following
> | [End Alternate Package Models] keyword. The package model names
> | listed under the [Alternate Package Models] must follow the
> | rules of the package model names associated with the
> | [Package Model] keyword. The package model names correspond
> | to the names of package models defined by [Define Package
> | Model] keywords. Simulation tools may offer users a facility
> | for choosing between the default package model and any of the
> | alternate package models, when analyzing occurances of the
> | [Component].
> |=============================================================================
> |
> [Alternate Package Models]
> |
> 208-pin_plastic_PQFP_package-even_mode | What more can be said here?
> 208-pin_plastic_PQFP_package-odd_mode | It's all in the name.
> 208-pin_ceramic_PQFP_package-even_mode | More comments and descriptions here.
> 208-pin_ceramic_PQFP_package-odd_mode | And some more here too.
> [End Alternate Package Models]
> |
> ******************************************************************************
>
> ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:
>
> Problem statement
>
> Some components are shipped in multiple package styles. Also, there are
> situations when the corner cases of a package are modeled with multiple
> package models. Currently, in these cases the user of the IBIS model has to
> manually edit the IBIS file to change the package model name that is called by
> the [Package Model] keyword in order to reference a different package model.
> This makes automated simulations difficult, if not impossible.
>
> Possible solutions
>
> Add a new, simple keyword to the IBIS specification which works similar to the
> already existing [Model Selector] keyword. This was proposed in the original
> BIRD.
>
> Add a secondary keyword to list package models that are alternates to the
> default package model given by [Package Model]. This is the currently
> proposed solution.
>
> ******************************************************************************
>
> ANY OTHER BACKGROUND INFORMATION:
>
> Several IBIS model users expressed their desire in private conversations and
> IBIS meetings to have such a package model selection mechanism in the IBIS
> specification to make their work easier.
>
> An alternate syntax was suggested by Bob Ross during an EMAIL and telephone
> correspondence on 10/25/99. The suggested syntax is identical to the [Model
> Selector] syntax, according to which the [Package Model Selector] would be
> assigned a name that is called by the (higher level) [Package Model] keyword.
> However, unlike in the [Model Selector] case, there is no need for calling the
> [Package Model Selector] from a higher level. This BIRD favors the simpler
> vs. the more consistent approach.
>
> Scott McMorrow made a request in an EMAIL on 11/12/99 to incorporate typ.,
> min., and max. columns in the list of package models under the model selector
> name to assist in automating the package model selection based on corner
> cases. According to the existing rules this is not possible, because the
> package model names are allowed to be up to 40 characters in length. Three
> package model names on the same line could add up to 122 characters, which
> violates the current 80 character per line rules of the IBIS specification.
>
> Further, package model names are allowed to include blank characters, which
> requires a delimiter other than the space or tab character between the
> typ., min., and max. columns. The usage of a new delimiter introduces another
> inconsistency in the IBIS specification, since spaces and/or tab characters
> are widely used as delimiters between columns in current IBIS versions.
>
> A technical dilemma regarding the automated selection of package models based
> on typ., min., and max. qualifiers remains to be answered also. What do typ.,
> min., and max. represent? Impedance, wave velocity, trace length, or perhaps
> the amount of cross talk? Simulation tool users will most likely make their
> choices based on individual preferences, possibly depending on project
> requirements. For this reason it seems to make more sense to give only a list
> that contains all of the package models without the typ., min., and max.
> qualifiers. The selection and automated usage of the various package models
> should then be done through a GUI or configuration mechanisms provided by the
> tool.
>
> The differences between the model name and package model name restrictions
> required a change even in this BIRD. The description field of the [Model
> Selector] keyword is separated by one or more space or tab character(s) from
> the model name. However, since package model names can contain blank
> characters, space or tab characters will not work as delimiters for the
> description field of the [Alternate Package Models] keyword.
>
> Since the contents of the description field is only used for informational
> purposes which does not effect the simulations I decided to use the comment
> character (|) as the delimiter for now. This option was actually discussed
> for the [Model Selector] also but voted down for the reason that tools reading
> an IBIS model have all the rights to ignore all comments, therefore a GUI
> would not know how to distinguish between a legitimate description and a
> meaningless comment. Does anyone have a better suggestion?
>
> Revision 64.2 changes 10-8-2000, Mike LaBonte:
>
> Added scoping requirements and mutually exclusive relationship with [Package
> Model]. Changed wording "... allows multiple package models to be listed" to
> "... allows multiple models to be listed for a package". The new phrasing
> implies that [Alternate Package Models] should be used to specify multiple
> models for one package, not models for multiple packages. It might be
> inappropriate to place package models with different pin assignments,
> thermal characteristics, etc. on a [Alternate Package Models] list, since
> these variations would normally require changes to other elements of the
> component model.
>
> Revision 64.3 changes 10-31-2000, Mike LaBonte:
>
> At the 10-27-2000 IBIS forum meeting it was pointed out that the original
> [Package Model Selector] keyword proposal was inconsistent in usage with the
> [Model Selector] keyword. A key point is that each [Model Selector] has a
> name that can be referred to in the [Pin] section as if it were the name of a
> [Model]. The [Package Model Selector] keyword, as proposed, had no name.
> This was ponted out earlier by Bob Ross. The [Alternate Package Models]
> proposal avoids the use of a named selector, and retains the usefulness of the
> existing [Package Model] keyword. At this time an [End Alternate Package
> Models] keyword is introduced, to reduce potential parsing ambiguity for the
> list of alternate package model names.
>
> Along with this change the title of the BIRD changes from "Package Model
> Selector" to "Alternate Package Models". A usage note explaining that
> the name values in the list refer to [Define Package Model] names is also
> added.
>
> ******************************************************************************
 
Received on Thu Nov 2 15:57:13 2000