Circuit Design With Vhdl

Circuit Design
w ith VHDL
Volnei A. Pedroni

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.
Includesbibliographical 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
621.39 0 5—dc22
2004040174
10 9 8 7 6 5 4 3 2 1

TLFeBOOK

To Claudia, Patricia, Bruno, and Ricardo

TLFeBOOK

TLFeBOOK

Contents

Preface

xi

I

CIRCUIT DESIGN

1

1

Introduction1.1
About VHDL
1.2
Design Flow
1.3
EDA Tools
1.4
Translation of VHDL Code into a Circuit
1.5
Design Examples

3
3
3
4
5
8

2

Code
2.1
2.2
2.3
2.4
2.5
2.6

Structure
Fundamental VHDL Units
LIBRARY Declarations
ENTITY
ARCHITECTURE
Introductory Examples
Problems

13
13
13
15
17
17
22

3

Data
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
3.10
3.11Types
Pre-Defined Data Types
User-Defined Data Types
Subtypes
Arrays
Port Array
Records
Signed and Unsigned Data Types
Data Conversion
Summary
Additional Examples
Problems

25
25
28
29
30
33
35
35
37
38
38
43

4

Operators and Attributes
4.1
Operators
4.2
Attributes
4.3
User-Defined Attributes
4.4
Operator Overloading

47
47
50
52
53

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viiiContents

4.5
4.6
4.7
4.8

GENERIC
Examples
Summary
Problems

54
55
60
61
65
65
67
69
78
81
84

5

Concurrent Code
5.1
Concurrent versus Sequential
5.2
Using Operators
5.3
WHEN (Simple and Selected)
5.4
GENERATE
5.5
BLOCK
5.6
Problems

6

Sequential Code
6.1
PROCESS
6.2
Signals and Variables
6.3
IF
6.4
WAIT
6.5
CASE
6.6
LOOP
6.7
CASE versus IF6.8
CASE versus WHEN
6.9
Bad Clocking
6.10 Using Sequential Code to Design Combinational Circuits
6.11 Problems

91
91
93
94
97
100
105
112
113
114
118
121

7

Signals and Variables
7.1
CONSTANT
7.2
SIGNAL
7.3
VARIABLE
7.4
SIGNAL versus VARIABLE
7.5
Number of Registers
7.6
Problems

129
129
130
131
133
140
151

8

State
8.1
8.2
8.3

159
159
160168

Machines
Introduction
Design Style #1
Design Style #2 (Stored Output)

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Contents

8.4
8.5

ix

Encoding Style: From Binary to OneHot
Problems

181
183

9

Additional Circuit Designs
9.1
Barrel Shifter
9.2
Signed and Unsigned Comparators
9.3
Carry Ripple and Carry Look Ahead Adders
9.4
Fixed-Point Division
9.5
Vending-Machine Controller
9.6
SerialData Receiver
9.7
Parallel-to-Serial Converter
9.8
Playing with a Seven-Segment Display
9.9
Signal Generators
9.10 Memory Design
9.11 Problems

187
187
191
194
198
202
208
211
212
217
220
225

II

SYSTEM DESIGN

231

10

Packages and Components
10.1 Introduction
10.2 PACKAGE
10.3 COMPONENT
10.4 PORT MAP
10.5 GENERIC MAP
10.6 Problems

233
233
234
236
244244
251

11

Functions and Procedures
11.1 FUNCTION
11.2 Function Location
11.3 PROCEDURE
11.4 Procedure Location
11.5 FUNCTION versus PROCEDURE Summary
11.6 ASSERT
11.7 Problems

253
253
256
265
266
270
270
271

12

Additional System Designs
12.1 Serial-Parallel Multiplier
12.2 Parallel Multiplier

275
275
279

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x

Contents

12.3
12.4
12.5...