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PrefaceThis book is intended for an introductory course in digital logic design, which is a basic
course in most electrical and computer engineering programs. A successful designer of
digital logic circuits needs a good understanding of basic concepts and a firm grasp of
computer-aided design (CAD) tools. The purpose of our book is to provide the desirable
balance between teaching the basic concepts and practical application through CAD tools.
To facilitate the learning process, the necessary CAD software is included as an integral
part of the book package.
A serious drawback of many books on digital logic design is that they cover too much
material. A book that covers a large number of topics is not easy to use in a classroom,
particularly if the topics are not covered in sufficient depth. Also, in their desire to provide
a vast amount of practical advice, the authors often make the text difficult to follow by the
students who are still struggling with the fundamental concepts. Our aim is to avoid both
of these problems.
The main goals of the book are (1) to teach students the fundamental concepts in
classical manual digital design and (2) illustrate clearly the way in which digital circuits
are designed today, using CAD tools. Even though modern designers no longer use manual
techniques, except in rare circumstances, our motivation for teaching such techniques is
to give students an intuitive feeling for how digital circuits operate. Also, the manual
techniques provide an illustration of the types of manipulations performed by CAD tools,
giving students an appreciation of the benefits provided by design automation. Throughout
the book, basic concepts are introduced by way of examples that involve simple circuit
designs, which we perform using both manual techniques and modern CAD-tool-based
methods. Having established the basic concepts, more complex examples are then provided,
using the CAD tools. Thus our emphasis is on modern design methodology to illustrate
how digital design is carried out in practice today.Technology and CAD Support
The book discusses modern digital circuit implementation technologies. We briefly discuss
SSI, as well as semi-custom and full-custom technologies. However, the emphasis is on
programmable logic devices (PLDs). This is the most appropriate technology for use in a
textbook for two reasons. First, PLDs are widely used in practice and are suitable for almost
all types of digital circuit designs. In fact, students are more likely to be involved in PLD-based
designs at some point in their careers than in any other technology. Second, circuits
are implemented in PLDs by end-user programming. Therefore, students can be provided
with an opportunity, in a laboratory setting, to implement the book’s design examples in
actual chips. Students can also simulate the behavior of their designed circuits on their own
computers. We use the two most popular types of PLDs for targeting of designs: complex
programmable logic devices (CPLDs) and field-programmable gate arrays (FPGAs).
Our CAD support is based on Altera MAX+plusII software. MAX+plusII provides
automatic mapping of a design into Altera CPLDs and FPGAs, which are among the most
widely used PLDs in the industry. The features of MAX+plusII that are particularly attractive
for our purposes are:- It is a commercial product. The version included with the book supports all major
features of the product. Students will be able to easily enter a design into the CAD
system, compile the design into a selected device (the choice of device can be changed
at any time and the design retargeted to a different device), simulate the functionality
and detailed timing of the resulting circuit, and if laboratory facilities are provided at
the student's school, implement the designs in actual devices.
- It provides for design entry using both hardware description languages (HDLs) and
schematic capture. In the book, weprovide examples of design using schematic capture,
but we emphasize the HDL-based design because it is the most efficient design method
to use in practice. We describe in detail the IEEE Standard Verilog language and use
it extensively in examples. The CAD system included with the book has a Verilog
compiler, which allows the student to automatically create circuits from the Verilog
code and implement these circuits in real chips.
- It can automatically target a design to various types of devices. This feature allows us
to illustrate the ways in which the architecture of the target device affects a designer's
circuit.
- It can be used on most types of popular computers. We expect that most students will
use the version of the software that runs on IBM-compatible computers (running any
version of Microsoft windows), which is provided with the book. However, through
Altera's university program the software is also available for other machines, such as
SUN or HP workstations.
AMAX+plusII CD-ROM is included with each copy of the book. Use of the software
is fully integrated into the book so that students can try, firsthand, all design examples. To
teach the students how to use this software, the book includes three, progressively advanced,
hands-on tutorials.Scope of the Book
Chapter 1 provides a general introduction to the process of designing digital systems. It
discusses the key steps in the design process and explains how CAD tools can be used to
automate many of the required tasks.
Chapter 2 introduces the basic aspects of logic circuits. It shows how Boolean algebra
is used to represent such circuits. It also gives the reader a first glimpse at Verilog, as an
example of a hardware description language that may be used to specify the logic circuits.
The electronic aspects of digital circuits are presented in Chapter 3. This chapter shows
how the basic gates are built using transistors and presents various factors that affect circuit
performance. The emphasis is on the latest technologies, with particular focus on CMOS
technology and programmable logic devices.
Chapter 4 deals with the synthesis of combinational circuits. It covers all aspects of
the synthesis process, starting with an initial design and performing the optimization steps
needed to generate a desired final circuit. It shows how CAD tools are used for this purpose.
Chapter 5 concentrates on circuits that perform arithmetic operations. It begins with
a discussion of how numbers are represented in digital systems and then shows how such
numbers can be manipulated using logic circuits. This chapter illustrates how Verilog can
be used to specify the desired functionality and how CAD tools provide a mechanism for
developing the required circuits. We chose to introduce the number representations at this
point, rather than in the very beginning of the book, to make the discussion more meaningful
and interesting, because we can immediately provide examples of how numerical
information may be processed by actual circuits.
Chapter 6 presents combinational circuits that are used as building blocks. It includes
the encoder, decoder, and multiplexer circuits. These circuits are very convenient for
illustrating the application of many Verilog constructs, giving the reader an opportunity to
discover more advanced features of Verilog.
Storage elements are introduced in Chapter 7. The use of flip-flops to realize regular
structures, such as shift registers and counters, is discussed. Verilog-specified designs of
these structures are included.
Chapter 8 gives a detailed presentation of synchronous sequential circuits (finite state
machines). It explains the behavior of these circuits and develops practical design techniques
for both manual and automated design.
Asynchronous sequential circuits are discussed in Chapter 9. While this treatment is
not exhaustive, it provides a good indication of the main characteristics of such circuits.
Even though the asynchronous circuits are not used extensively in practice, they should be
studied because they provide an excellent vehicle for gaining a deeper understanding of
the operation of digital circuits in general. They illustrate the consequences of propagation
delays and race conditions that may be inherent in the structure of a circuit.
Chapter 10 is a discussion of a number of practical issues that arise in the design of real
systems. It highlights problems often encountered in practice and indicates how they can
be overcome. Examples of larger circuits illustrate a hierarchical approach in designing
digital systems. Complete Verilog code for these circuits is presented.
Chapter 11 introduces the topic of testing. A designer of logic circuits has to be aware
of the need to test circuits and should be conversant with at least the most basic aspects of
testing.
Appendix Aprovides a complete summary of Verilog features. Although use of Verilog
is integrated throughout the book, this appendix provides a convenient reference that the
reader can consult from time to time when writing Verilog code.
Appendices B, C, and D contain a sequence of tutorials on the MAX+plusII CAD tools.
This material is suitable for self-study; it shows the student in a step-by-step manner how
to use the CAD software provided with the book.
Appendix E gives detailed information about the devices used in illustrative examples.
It also includes a brief discussion of TTL technology.What Can Be Covered in a Course
All the material in the book can be covered in 2 one-quarter courses. A good coverage
of the most important material can be achieved in a single one-semester, or even a one-quarter,
course. This is possible only if the instructor does not spend too much time teaching
the intricacies of Verilog and CAD tools. To make this approach possible, we organized the Verilog material in a modular style that is conducive to self-study. Our experience in
teaching different classes of students at the University of Toronto shows that the instructor
may spend only 2 to 3 lecture hours on Verilog, concentrating mostly on the specification
of sequential circuits. The Verilog examples given in the book are largely self-explanatory,
and students can understand them easily. Moreover, the instructor need not teach how to use
the CAD tools, because the MAX+plusII tutorials in Appendices B, C, and D are suitable
for self-study.
The book is also suitable for a course in logic design that does not include exposure to
Verilog. However, some knowledge of Verilog, even at a rudimentary level, is beneficial
to the students, and it is a great preparation for a job as a design engineer.One-Semester Course
A natural starting point for formal lectures is Chapter 2. The material in Chapter 1 is
a general introduction that serves as a motivation for why logic circuits are important and
interesting; students can read and understand this material easily.
The following material should be covered in lectures:
•Chapter 2—all sections.
•Chapter 3—sections 3.1 to 3.7. Also, it is useful to cover sections 3.8 and 3.9 if the
students have some basic knowledge of electrical circuits.
•Chapter 4—sections 4.1 to 4.7 and section 4.12.
•Chapter 5—sections 5.1 to 5.5.
•Chapter 6—all sections.
•Chapter 7—all sections.
•Chapter 8—sections 8.1 to 8.9.
If time permits, it would also be very useful to cover sections 9.1 to 9.3 and section 9.6 in
Chapter 9, as well as one or two examples in Chapter 10.One-Quarter Course
In a one-quarter course the following material can be covered:
•Chapter 2—all sections.
•Chapter 3—sections 3.1 to 3.3.
•Chapter 4—sections 4.1 to 4.5 and section 4.12.
•Chapter 5—sections 5.1 to 5.3 and section 5.5.
•Chapter 6—all sections.
•Chapter 7—sections 7.1 to 7.10 and section 7.13.
•Chapter 8—Sections 8.1 to 8.5.A More Traditional Approach
The material in Chapters 2 and 4 introduces Boolean algebra, combinational logic circuits,
and basic minimization techniques. Chapter 2 provides initial exposure to these topics using
onlyAND,OR, NOT, NAND,and NORgates. Then Chapter 3 discusses the implementation
technology details, before proceeding with the synthesis techniques and other types of gates in Chapter 4. The material in Chapter 4 is appreciated better if students understand the
technological reasons for the existence of NAND, NOR, and XOR gates, and the various
programmable logic devices.
An instructor who favors a more traditional approach may cover Chapters 2 and 4 in
succession. To understand the use of NAND, NOR, and XOR gates, it is necessary only
that the instructor provide a functional definition of these gates.Verilog
Verilog is a complex language, which some instructors feel is too hard for beginning students
to grasp. We fully appreciate this issue and have attempted to solve it. It is not necessary
to introduce the entire Verilog language. In the book we present the important Verilog
constructs that are useful for the design and synthesis of logic circuits. Many other language
constructs, such as those that have meaning only when using the language for simulation
purposes, are omitted. The Verilog material is introduced gradually, with more advanced
features being presented only at points where their use can be demonstrated in the design
of relevant circuits.
The book includes more than 140 examples of Verilog code. These examples illustrate
how Verilog is used to describe a wide range of logic circuits, from those that contain only
a few gates to those that represent digital systems such as a simple processor.Homework Problems
More than 400 homework problems are provided in the book. Solutions to these problems
are available to instructors in the Solutions Manual that accompanies the book.Laborator
The book can be used for a course that does not include laboratory exercises, in which case
students can get useful practical experience by simulating the operation of their designed
circuits by using the CAD tools provided with the book. If there is an accompanying laboratory,
then a number of design examples in the book are suitable for laboratory experiments.
Additional experiments are available on the authors' website.Acknowledgments
We wish to express our thanks to the people who have helped during the preparation of the
book. Kelly Chan helped with the technical preparation of the manuscript. Dan Vranesic
produced a substantial amount of artwork. He and Deshanand Singh also helped with the
preparation of the solutions manual. The reviewers, William Barnes, New Jersey Institute
of Technology; James Clark, McGill University; Stephen DeWeerth, Georgia Institute of
Technology; Clay Gloster, Jr., North Carolina State University (Raleigh); Carl Hamacher,
Queen’s University; Wei-Ming Lin, University of Texas (Austin); Wayne Loucks, University
of Waterloo; Chris Myers, University of Utah; James Palmer, Rochester Institute of Technology; Gandhi Puvvada, University of Southern California; Teodoro Robles, Milwaukee
School of Engineering; Tatyana Roziner, Boston University; Rob Rutenbar, Carnegie
Mellon University; Charles Silio, Jr., University of Maryland; Scott Smith, University of
Missouri (Rolla); Arun Somani, Iowa State University; and Zeljko Zilic, McGill University
provided constructive criticism and made numerous suggestions for improvements. We
are grateful to the Altera Corporation for providing the MAX+plusII CAD system. The
support of McGraw-Hill people has been exemplary. We truly appreciate the help of Kelley
Butcher, Catherine Fields Shultz, Michaela Graham, Betsy Jones, Kara Kudronowicz,
Carlise Paulson, Jill Peter, John Wannemacher, and Michelle Whitaker.Stephen Brown and Zvonko Vranesic |
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2003 McGraw-Hill Higher Education