[IBIS] TSIRD2 - Binary Format Support

All:

TSIRD2 which refrences

   http://www.eda.org/ibis/tsirds/tsird2.pdf

is submitted for introduction at the June 11, 2010
IBIS teleconference meeting

Bob

                 Touchstone Issue Resolution Document (TSIRD)

TSIRD ID#: 2
ISSUE TITLE: Binary Format Support
REQUESTER: Michael Mirmak, Intel Corp. for Interconnect Task Group
DATE SUBMITTED: June 9, 2010
DATE ACCEPTED BY IBIS OPEN FORUM:

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STATEMENT OF THE ISSUE:

Touchstone files describing large numbers of ports and/or port interactions
can have significant filesizes (in the tens of megabytes). Such files can
be difficult to distribute and parse.

This TSIRD proposes an optional binary format for the numerical data under the
[Network Data] and [Noise Data] keywords. This format would replace the ASCII
data under those keywords in earlier Touchstone versions.

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STATEMENT OF THE RESOLVED SPECIFICATIONS:

TSIRD2 proposes adding a new keyword to support binary data representation of
network and noise data. This keyword, [Binary], is hierarchically scoped
within the [Network Data] and [Noise Data] keywords in Touchstone.

A full set of rules is described in tsird2.pdf:

   http://www.eda.org/ibis/tsirds/tsird2.pdf

This file's text is intended for inclusion as a new keyword section in the
Touchstone specification.

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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:

Note that a binary format for Touchstone was originally proposed by Sam
Chitwood of Sigrity in July 2007. Anecdotal data from IBIS Ad Hoc Interconnect
Task Group members suggests binary data sets occupy only 20 to 33 percent of the
space taken by ASCII sets describing the same structures. Connector and package
interconnects are the most likely candidates for binary treatment.

In the course of development, several decisions were made.

- This proposal applies to Touchstone 2.1 and above. While the original
   proposal was related to a Touchstone 1.0 application, the formal implementation
   of a binary option would be adopted in practice with a new Touchstone format.
   Tool vendors are not likely to add such a feature to a legacy format.

- The full set of Touchstone keywords is available when [Binary] is used. There
   was consideration that the [Noise Data] keyword and [End] keyword would be
   excluded, as the end of the binary data section would thought to be hard to
   determine in a mixed-format environment. However, there is sufficient size
   information in the [Binary] section, in combination with the other keyword
   options, for determining exactly where the binary data ends.

- As a generalization, the [Binary] keyword may be used for either or both
   [Network Data] and [Noise Data].

- An explicit set of arguments (32-Bit 64-Bit, Big-Endian, Little-Endian) was
   chosen for clarity, rather than a more cryptic, packed 3-letter sequence (such
   as "FDB" for Floating Point, Double, Big-Endian).

- The frequency precision is handled separately from the N-port data or noise
   data precision because higher precision frequency information is sometimes
   required for reasonance detection. This detection does not necesarily require
   similarly high precision for the data entries.

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ANY OTHER BACKGROUND INFORMATION:

The binary format assumes the existence of a conversion utility, possibly part
of a parsing program, that would convert a legal Touchstone 2.x file using
ASCII data into a legal Touchstone 2.x file using binary data with the appropriate
[Binary] keyword and associated arguments.

While only 32- and 64-bit architectures are supported here, the specification
can be easily extended in future to cover alternatives.

Many people in the IBIS Ad Hoc Interconnect Task Group made key suggestions or
observations in preparing this material.

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-- 
Bob Ross
Teraspeed Consulting Group LLC     Teraspeed Labs
121 North River Drive              13610 SW Harness Lane
Narragansett, RI 02882             Beaverton, OR 97008
401-284-1827                       503-430-1065
http://www.teraspeed.com           503-246-8048 Direct
bob@teraspeed.com
Teraspeed is a registered service mark of Teraspeed Consulting Group LLC
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