VHDL Programming

PREFACE

This is the fourth version of the book and this version now not only provides

VHDL language coverage but design methodology information as well. This

version will guide the reader through the process of creating a VHDL

design, simulating the design, synthesizing the design, placing and routing

the design, using VITAL simulation to verify the final result, and a new

technique called At-Speed debugging that provides extremely fast design

verification. The design example in this version has been updated to reflect

the new focus on the design methodology.

This book was written to help hardware design engineers learn how to

write good VHDL design descriptions. The goal is to provide enough VHDL

and design methodology information to enable a designer to quickly write

good VHDL designs and be able to verify the results. It will also attempt

to bring the designer with little or no knowledge of VHDL, to the level of

writing complex VHDL descriptions. It is not intended to show every pos-

sible construct of VHDL in every possible use, but rather to show the de-

signer how to write concise, efficient, and correct VHDL descriptions of

hardware designs.

This book is organized into three logical sections. The first section of the

book will introduce the VHDL language, the second section walks through

a VHDL based design process including simulation, synthesis, place and

route, and VITAL simulation; and the third section walks through a design

example of a small CPU design from VHDL capture to final gate-level

implementation, and At-Speed debugging. At the back of the book are

included a number of appendices that contain useful information about the

language and examples used throughout the book.

In the first section VHDL features are introduced one or more at a time.

As each feature is introduced, one or more real examples are given to show

how the feature would be used. The first section consists of Chapters 1

through 8, and each chapter introduces a basic description capability of

VHDL. Chapter 1 discusses how VHDL design relates to schematic based

design, and introduces the basic terms of the language. Chapter 2 describes

some of the basic concepts of VHDL, including the different delay mecha-

nisms available, how to use instance specific data, and defines VHDL dri-

vers. Chapter 2 discusses concurrent statements while Chapter 3 introduces

the reader to VHDL sequential statements. Chapter 4 talks about the wide