DIGITAL DESIGN FLOW OPTIONS
ABSTRACT
VLSI (Very Large Scale Integration) IC design flow is a term used to
describe the process of chip design. The circuit designer/design group uses a
multitude of computer aided design tools throughout the design flow to tape out an
integrated circuit IC. There are numerous computer aided design (CAD) tools
available commercially to help such designers in design. The design tools and the
order in which they are used is termed as the design flow.
CAD tools however do have certain problems associated with them. Cost,
accessibility, compatibility and reliability are a few of such problems. At the
university level, usability, tutorials and adequate documentation is needed to
facilitate students to adapt and familiarize themselves with the CAD tool suites in a
short time.
In mixed signal chips, there are two distinct phases of design, the analog
and the digital part. The analog part of the chip (probably containing a few hundred
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transistors) consumes a considerable amount of time to design. The digital part of
the chip (probably containing tens of thousands to a million transistors) needs to be
developed in a relatively short period of time. Thus design team needs to place a
few thousand gates quickly and reliably. To support this, the choice of CAD tools
becomes critical. A good CAD tool can drastically reduce the time required to
design a large digital block.
The scope of this thesis is to search for an optimal digital design flow. The
aim is to use a set of commercial and open sourced tools and bring digital logic
design to such a stage that the design can be shipped for fabrication or attached to
an analog entity for fabricated into a mixed signal chip. The stress in this thesis is
going to be on evolving a streamlined design flow, which is quick, cheap, reliable
and acceptable. Conclusions will be reached as to how a particular tool is best
suited for each stage of design. These design suites will be compared and
contrasted with respect to various qualities like cost, accessibility, usability, etc.
Most non-commercial CAD tools fail to meet the industry’s requirements
when the design becomes technology specific. Most industrially accepted CAD
tools are expensive. It is here that a cheaper design alternative is required. Solutions
to this problem using Electric and TestBencher are suggested in this thesis.
In this document, the primary focus is on three tools, TestBencher, X-HDL3
and Electric. These CAD tools were chosen, as they seemed ideal for a university
environment.
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All the chapters start with a brief explanation of a design stage. After a brief
explanation, every chapter is further subdivided into various sections. Each section
deals with a particular aspect of design and how the design can be completed using
one of the CAD tools. Throughout this document an example based approach is
adopted. The examples chosen are simple circuits to increase readability.
ACKNOWLEDGMENTS
I would like to thank my friend Nipa for her continuous motivation, moral
support, encouragement and love. I would like to thank Prof. DeGroat for her
suggestions, support, guidance and the inspiration I got while working with her
during the course of my masters degree. I am especially indebted to Prof. Bibyk for
all his invaluable suggestions, advice, support, guidance and help.
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VITA
Dec 24, 1977 Born – Guntur, India.
1995 – 1999 B.E. Electrical & Electronics
Engineering,
Bangalore University,
Bangalore, India.
1999- present Masters student,
The Ohio State University