Book Preface

With the strong impact of digital technology on our everyday lives, it is not surprising that a course in digital concepts and design is a standard requirement for majors in computer engineering, computer science, and electrical engineering. An introductory course is frequently encountered in the first or second year of their undergraduate programs. Additional courses are then provided to refine and extend the basic concepts of the introductory course.

This book is suitable for an introductory course in digital principles with em-phasis on logic design as well as for a more advanced course. With the exception of the appendix, it assumes no background on the part of the reader. The intent of the author is not to just present a set of procedures commonly encountered in digital design but, rather, to provide justifications underlying such procedures. Since no background is assumed, the book can be used by students in computer engineering, computer science, and electrical engineering.

The approach taken in this book is a traditional one. That is, emphasis is on the presentation of basic principles of logic design and the illustration of each of these principles. The philosophy of the author is that a first course in logic design should establish a strong foundation of basic principles as provided by a more traditional approach before engaging in the use of computer-aided design tools. Once basic concepts are mastered, the utilization of design software becomes more meaningful and allows the student to use the software more effectively. Thus, it is the understanding of basic principles on which this book focuses and the application of these principles to the analysis and design of combinational and sequential logic networks. Each topic is approached by first introducing the basic theory and then illustrating how it applies to design. For those people who want to use CAD tools, we have included a CD-ROM containing Altera MAX+plus II 10.1 Student Edition, as well as software tutorials in an Appendix.

SCOPE OF THE BOOK

Chapter 1 discusses the differences between continuous, i.e., analog, and discrete, i.e., digital, networks and devices. Then, the basic operation of the digital computer is introduced as an example of a system that utilizes most of the concepts presented in the remaining chapters. The chapter concludes with an overview of the topics that will be introduced.

In Chapter 2 the general concepts of positional number systems, arithmetic, and conversion techniques are introduced. This material is developed for arbitrary positive integer bases rather than simply for the binary number system to emphasize the similarity of all positional number systems and their manipulations. Then, various codes and their properties are discussed with emphasis on error detection and correction.

The two-valued Boolean algebra is introduced in Chapter 3. How Boolean expressions are written, manipulated, and simplified is presented. Since there is a one-to- one correspondence between the two-valued Boolean algebra and logic networks, it is then shown how the algebra can serve as a mathematical model for the behavior and structure of combinational logic networks. The chapter concludes with a discussion of the gate properties that are relevant to logic networks, i.e., noise margin, fan-out, propagation delays, and power dissipation.

An important application of the Boolean algebra is to obtain those expressions which can best be associated with optimal networks. Under the assumption that the reduction in the delay time of a network is of paramount importance, it is possible to obtain efficient networks by systematic procedures. Two methods for obtaining minimal expressions are presented in Chapter 4. The first method, Karnaugh maps, is a graphical procedure that permits minimal expressions to be obtained very rapidly. However, since the procedure relies upon the recognition of patterns, there is a limit to the complexity of a problem for which the procedure is effective. This limit seems to be problems of six variables. A second method for obtaining minimal expressions is the Quine-McCluskey method. This method involves just simple mathematical manipulations. For problems with many variables, the Quine-McCluskey method can be carried out on a digital computer. The concepts of both approaches are then extended to a set of Boolean expressions describing multiple-output networks. The chapter concludes with a variation of the Karnaugh map concept, called variable-entered Karnaugh maps, in which Boolean functions can appear as map entries.

Chapter 5 is concerned with several MSI and LSI components. The intent of this chapter is to investigate combinational networks that are commonly encountered in digital systems. Several types of adders and subtracters are discussed. These include binary and decimal adders as well as high-speed adders using the carry lookahead concept. Also included in this chapter are discussions on comparators, decoders, encoders, and multiplexers. In the case of decoders and multiplexers, attention is given to their use as generic logic design devices. The final part of the chapter involves the three basic structures of programmable logic devices: programmable read-only memories, programmable logic arrays, and programmable array logic devices. Emphasis is placed on their utilization for the realization of logic networks, with special attention given to their strengths and weaknesses and the constraints placed on a logic design utilizing them.

Chapter 6 begins the presentation on sequential logic networks. In this chapter, various types of flip-flops, i.e., JK, D, T, and SR flip-flops, are introduced. The operational behavior of the three categories of flip-flops, i.e., latches, edge-triggered, and master-slave flip-flops, is discussed in detail. The remainder of the chapter is concerned with some simple flip-flop applications, in particular, registers and counters. Ripple and synchronous counters are presented and compared. The chapter concludes with a general design procedure for synchronous counters. This procedure serves as a basis for

Chapters 7 and 8 involve clocked synchronous sequential networks. In Chapter 7 the classic Mealy and Moore models of a synchronous sequential network are pre- sented. First, these networks are analyzed to establish various tabular representations of network behavior. Then, the process is reversed and synthesis is discussed. Chapter 8 also involves the design of clocked synchronous sequential networks; however, this time using the algorithmic state machine model. The relationship between the classic Mealy/Moore models and the algorithmic state machine model is discussed as well as the capability of the algorithmic state machine model to handle the controlling of an architecture of devices.

In Chapter 9 asynchronous sequential networks are studied. Paralleling the approach taken for synchronous sequential networks, the analysis of asynchronous sequential networks is first undertaken and then, by reversing the analysis procedure, the synthesis of these networks is presented. Included in this chapter is also a discussion on static and dynamic hazards. Although these hazards occur in combinational networks, their study is deferred to this chapter, since these hazards can have a major effect on asynchronous network behavior. A great deal of attention is given to the many design constraints that must be satisfied to achieve a functional design of an asynchronous network. In addition to the static and dynamic hazards, the concepts of races, the importance of the state assignment, and the effects of essential hazards are addressed.

An appendix on digital electronics is included for completeness. It is not intended to provide an in-depth study on digital electronics, since such a study should be reserved for a course in itself. Rather, its inclusion is to provide the interested reader an introduction to actual circuits that can occur in digital systems and the source of constraints placed upon a logic designer. For this reason, the appendix does not delve into circuit design but, rather, only into the analysis of electronic digital circuits. Emphasis is placed on the principles of operation of TTL, ECL, and MOS logic circuits. Since circuits are analyzed, the appendix does assume the reader has an elementary knowledge of linear circuit analysis. In particular, the reader should be familiar with Ohm’s law along with Kirchhoff’s current and voltage laws. Another appendix with software tutorials is also included. These tutorials, provided by two contributors, include one on Altera MAX+plus II 10.1 Student Edition and one on LogicWorks TM 4. The tutorials are meant to provide basic introductions to these tools for those people who are using them in their course.

HOMEWORK PROBLEMS

With the exception of Chapter 1, each chapter includes a set of problems. Some of these problems provide for reinforcement of the reader’s understanding of the material, some extend the concepts presented in the chapter, and, finally, some are applications-oriented.

ADDITIONAL RESOURCES

The expanded book website at http://www.mhhe.com/givone includes a downloadable version of the Solutions Manual for instructors only and PowerPoint slides. There are also a variety of labs using both the Altera Software and LogicWorks. A CD-ROM containing Altera’s MAX+plus II CAD software and Multisim 2001 is included free with every copy of the book.