46183Pedroninew 2004-10-11 14:06 Page 1 Circuit Design Circuit Circuit Design with VHDL Volnei A. Pedroni This textbook teaches VHDL using system examples com- bined with programmable logic and supported by laboratory exercises. While other textbooks concentrate only on lan- guage features, Circuit Design with VHDL offers a fully inte- grated presentation of VHDL and design concepts by including a large number of complete design examples, illustrative circuit diagrams, a review of fundamental design concepts, fully explained solutions, and simulation results. The text presents the information concisely yet completely, discussing in detail all indispensable features of the VHDL synthesis. The book is organized in a clear progression, with the first part covering the circuit level, treating foundations of VHDL and fundamental coding, while the second part cov- ers the system level (units that might be located in a library for code sharing, reuse, and partitioning), expanding upon the earlier chapters to discuss system coding. Part I, “Circuit Design,” examines in detail the back- ground and coding techniques of VHDL, including code structure, data types, operators and attributes, concurrent with Circuit Design and sequential statements and code, objects (signals, vari- ables, and constants), design of finite state machines, and examples of additional circuit designs. Part II, “System with Design,” builds on the material already presented, adding VHDL elements intended mainly for library allocation; it examines VHDL packages and components, functions and procedures, and additional examples of system design. Appendixes on pro- Volnei A. Pedroni grammable logic devices (PLDs/FPGAs) and synthesis tools follow Part II. The book’s highly original approach of teach- ing through extensive system examples, as well as its unique integration of VHDL and design, makes it suitable both for use by students in computer science and electrical engineering. P Volnei A. Pedroni earned his Ph.D. in electrical engineering edroni from Caltech. He is currently Professor of Electrical Engineering at CEFET-PR (Federal Center of Technological Education of Parana), Brazil. The MIT Press Massachusetts Institute of Technology Cambridge, Massachusetts 02142 http://mitpress.mit.edu ,!7IA2G2-bgcceb!:t;K;k;K;k 0-262-16224-5 TLFeBOOK Circuit Design with VHDL TLFeBOOK TLFeBOOK Circuit Design with VHDL Volnei A. Pedroni MIT Press Cambridge, Massachusetts London, England TLFeBOOK 6 2004 Massachusetts Institute of Technology All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means (including photocopying, recording, or information storage and retrieval) without permission in writing from the publisher. This book was set in Times New Roman on 3B2 by Asco Typesetters, Hong Kong and was printed and bound in the United States of America. Library of Congress Cataloging-in-Publication Data Pedroni, Volnei A. Circuit design with VHDL/Volnei A. Pedroni. p. cm. Includes bibliographical references and index. ISBN 0-262-16224-5 (alk. paper) 1. VHDL (Computer hardware description language) 2. Electronic circuit design. 3. System design. I. Title. TK7885.7.P43 2004 621.3905—dc22 2004040174 10 987654321 TLFeBOOK To Claudia, Patricia, Bruno, and Ricardo TLFeBOOK TLFeBOOK Contents Preface xi I CIRCUIT DESIGN 1 1 Introduction 3 1.1 About VHDL 3 1.2 Design Flow 3 1.3 EDA Tools 4 1.4 Translation of VHDL Code into a Circuit 5 1.5 Design Examples 8 2 Code Structure 13 2.1 Fundamental VHDL Units 13 2.2 LIBRARY Declarations 13 2.3 ENTITY 15 2.4 ARCHITECTURE 17 2.5 Introductory Examples 17 2.6 Problems 22 3 Data Types 25 3.1 Pre-Defined Data Types 25 3.2 User-Defined Data Types 28 3.3 Subtypes 29 3.4 Arrays 30 3.5 Port Array 33 3.6 Records 35 3.7 Signed and Unsigned Data Types 35 3.8 Data Conversion 37 3.9 Summary 38 3.10 Additional Examples 38 3.11 Problems 43 4 Operators and Attributes 47 4.1 Operators 47 4.2 Attributes 50 4.3 User-Defined Attributes 52 4.4 Operator Overloading 53 TLFeBOOK viii Contents 4.5 GENERIC 54 4.6 Examples 55 4.7 Summary 60 4.8 Problems 61 5 Concurrent Code 65 5.1 Concurrent versus Sequential 65 5.2 Using Operators 67 5.3 WHEN (Simple and Selected) 69 5.4 GENERATE 78 5.5 BLOCK 81 5.6 Problems 84 6 Sequential Code 91 6.1 PROCESS 91 6.2 Signals and Variables 93 6.3 IF 94 6.4 WAIT 97 6.5 CASE 100 6.6 LOOP 105 6.7 CASE versus IF 112 6.8 CASE versus WHEN 113 6.9 Bad Clocking 114 6.10 Using Sequential Code to Design Combinational Circuits 118 6.11 Problems 121 7 Signals and Variables 129 7.1 CONSTANT 129 7.2 SIGNAL 130 7.3 VARIABLE 131 7.4 SIGNAL versus VARIABLE 133 7.5 Number of Registers 140 7.6 Problems 151 8 State Machines 159 8.1 Introduction 159 8.2 Design Style #1 160 8.3 Design Style #2 (Stored Output) 168 TLFeBOOK Contents ix 8.4 Encoding Style: From Binary to OneHot 181 8.5 Problems 183 9 Additional Circuit Designs 187 9.1 Barrel Shifter 187 9.2 Signed and Unsigned Comparators 191 9.3 Carry Ripple and Carry Look Ahead Adders 194 9.4 Fixed-Point Division 198 9.5 Vending-Machine Controller 202 9.6 Serial Data Receiver 208 9.7 Parallel-to-Serial Converter 211 9.8 Playing with a Seven-Segment Display 212 9.9 Signal Generators 217 9.10 Memory Design 220 9.11 Problems 225 II SYSTEM DESIGN 231 10 Packages and Components 233 10.1 Introduction 233 10.2 PACKAGE 234 10.3 COMPONENT 236 10.4 PORT MAP 244 10.5 GENERIC MAP 244 10.6 Problems 251 11 Functions and Procedures 253 11.1 FUNCTION 253 11.2 Function Location 256 11.3 PROCEDURE 265 11.4 Procedure Location 266 11.5 FUNCTION versus PROCEDURE Summary 270 11.6 ASSERT 270 11.7 Problems 271 12 Additional System Designs 275 12.1 Serial-Parallel Multiplier 275 12.2 Parallel Multiplier 279 TLFeBOOK x Contents 12.3 Multiply-Accumulate Circuits 285 12.4 Digital Filters 289 12.5 Neural Networks 294 12.6 Problems 301 Appendix A: Programmable Logic Devices 305 Appendix B: Xilinx ISE B ModelSim Tutorial 317 Appendix C: Altera MaxPlus II B Advanced Synthesis Software Tutorial 329 Appendix D: Altera Quartus II Tutorial 343 Appendix E: VHDL Reserved Words 355 Bibliography 357 Index 359 TLFeBOOK Preface Structure of the Book The book is divided into two parts: Circuit Design and System Design. The first part deals with everything that goes directly inside the main code, while the second deals with units that might be located in a library (for code sharing, reuse, and partitioning). In summary, in Part I we study the entire background and coding techniques of VHDL, which includes the following: Code structure: libraries, entity, architecture (chapter 2) Data types (chapter 3) Operators and attributes (chapter 4) Concurrent statements and concurrent code (chapter 5) Sequential statements and sequential code (chapter 6) Objects: signals, variables, constants (chapter 7) Design of finite state machines (chapter 8) And, finally, additional circuit designs are presented (chapter 9). Then, in Part II we simply add new building blocks, which are intended mainly for library allocation, to the material already presented. The structure of Part II is the following: Packages and components (chapter 10) Functions and procedures (chapter 11) Finally, additional system designs are presented (chapter 12). Distinguishing Features The main distinguishing features of the book are the following: It teaches in detail all indispensable features of VHDL synthesis in a concise format. The sequence is well established. For example, a clear distinction is made between what is at the circuit level (Part I) versus what is at the system level (Part II). The foundations of VHDL are studied in chapters 1 to 4, fundamental coding in chapters 5 to 9, and finally system coding in chapters 10 to 12. Each chapter is organized in such a way to collect together related information as closely as possible. For instance, concurrent code is treated collectively in one chap- TLFeBOOK xii Preface ter, while sequential code is treated in another; data types are discussed in one chap- ter, while operators and attributes are in another; what is at the circuit level is seen in one part of the book, while what is at the system level is in another. While books on VHDL give limited emphasis to digital design concepts, and books on digital design discuss VHDL only briefly, the present work completely integrates them. It is indeed a design-oriented approach. To achieve the above-mentioned integration between VHDL and digital design, the following steps are taken: a large number of complete design examples (rather than sketchy or partial solutions) are presented; illustrative top-level circuit diagrams are always shown; fundamental design concepts are reviewed; the solutions are explained and commented; the circuits are always physically implemented (using programmable logic devices); simulation results are always included, along with analysis and comments; finally, appendices on programmable devices and synthesis tools are also included. Audience The book is intended as a text for any of the following EE/CS courses: VHDL Automated Digital Design Programmable Logic Devices Digital Design (basic or advanced) It is also a supporting text for in-house courses in any of the areas listed above, particularly for vendor-provided courses on VHDL and/or programmable logic devices. Acknowledgments To the anonymous reviewers for their invaluable comments and suggestions. Special thanks also to Ricardo P. Jasinski and Bruno U. Pedroni for their reviews and comments.