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Efficient File Format for the Abridged Description of Hardware

IP.com Disclosure Number: IPCOM000122825D
Original Publication Date: 1998-Jan-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 8 page(s) / 268K

Publishing Venue

IBM

Related People

Paredes, JA: AUTHOR

Abstract

The new file format, Net list and Graphic Description format (NGD), is suitable for describing hardware in a complete and simple manner. It contains all the necessary means for showing connectivity to parts, trace and layer information, as well as part placement and geometry information for displaying the actual hardware in a computer screen. The format is very simple to decode and understand so that software that read in files in the NGD format can be written quickly.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 20% of the total text.

Efficient File Format for the Abridged Description of Hardware

      The new file format, Net list and Graphic Description format
(NGD), is suitable for describing hardware in a complete and simple
manner.  It contains all the necessary means for showing connectivity
to parts, trace and layer information, as well as part placement and
geometry information for displaying the actual hardware in a computer
screen.  The format is very simple to decode and understand so that
software that read in files in the NGD format can be written quickly.

      Fig. 1 is a description of the main sections of the NGD file
format.  All byte alignment is in little endian (bit 0 = lsb).  There
are four main sections in a NGD file.  The sections are:
  1.  the net description section,
  2.  the part description section,
  3.  the pin description section, and
  4.  the via description section.

      All sections are very similar, requiring minimal changes in
code to implement the reading of a section once a previous section
has been read.

      Each section contains sub-sections required to describe the
section in more detail.  It is not required for every NGD file to
implement all sections and sub-sections, but every file must have at
least one pin per net and one pin per part, for it would not make
sense to have a pin unassociated with a net or part, a net that does
not connect to a pin, or a part with no pins.
                       +-----------------------------+
                       | Section 1: Net Description  |
                       +-----------------------------+
                       | Section 2: Part Description |
                       +-----------------------------+
                       | Section 3: Pin Description  |
                       +-----------------------------+
                       | Section 4: Via Description  |
                       +-----------------------------+

            Fig. 1 Main 4 Sections of the NGD File Format

Each section is described below:

      The first section describes point-to-point net connectivity to
pins and vias as well as trace information.  Every net must have at
least one pin and must have a name length of at least two (including
null terminator).  Also, all the nets are sorted according to their
names to facilitate implementing fast search algorithms.  This
section is divided into six sub-sections, as shown in Fig, 2.

      The NEXT sub-section specifies the number of bytes to move from
the beginning of the net in order to reach the next net.  This has
the effect of creating a linked list structure for the nets within
the file  itself.  It minimizes the overhead of reading and
traversing the file to  find a a particular net.  The software need
n...