Brock J. LaMeres - Quick Start Guide to VHDL

Brock J. LaMeres

Quick Start Guide to VHDL

Brock J. LaMeres

Department of Electrical & Computer Engineering, Montana State University, Bozeman, MT, USA

ISBN 978-3-030-04515-9 e-ISBN 978-3-030-04516-6

https://doi.org/10.1007/978-3-030-04516-6

Library of Congress Control Number: 2018963722

Springer Nature Switzerland AG 2019

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Preface

The classical digital design approach (i.e., manual synthesis and minimization of logic) quickly becomes impractical as systems become more complex. This is the motivation for the modern digital design flow, which uses hardware description languages (HDL) and computer-aided synthesis/minimization to create the final circuitry. The purpose of this book is to provide a quick start guide to the VHDL language, which is one of the two most common languages used to describe logic in the modern digital design flow. This book is intended for anyone that has already learned the classical digital design approach and is ready to begin learning HDL-based design. This book is also suitable for practicing engineers that already know VHDL and need quick reference for syntax and examples of common circuits. This book assumes that the reader already understands digital logic (i.e., binary numbers, combinational and sequential logic design, finite state machines, memory, and binary arithmetic basics).

Since this book is designed to accommodate a designer that is new to VHDL, the language is presented in a manner that builds foundational knowledge first before moving into more complex topics. As such, Chaps. as they use the types std_logic and std_logic_vector . For a VHDL novice, understanding the history and fundamentals of the VHDL base release will help form a comprehensive understanding of the language; thus it is recommended that the early chapters are covered in the sequence they are written.

Brock J. LaMeres

Bozeman, MT, USA

Acknowledgments

For Alexis. The world is a better place because you are in it.

Contents

The purpose of a hardware description languages is to describe digital circuitry using a text-based language. HDLs provide a means to describe large digital systems without the need for schematics, which can become impractical in very large designs. HDLs have evolved to support logic simulation at different levels of abstraction. This provides designers the ability to begin designing and verifying functionality of large systems at a high level of abstraction and postpone the details of the circuit implementation until later in the design cycle. This enables a top-down design approach that is scalable across different logic families. HDLs have also evolved to support automated synthesis, which allows the CAD tools to take a functional description of a system (e.g., a truth table) and automatically create the gate-level circuitry to be implemented in real hardware. This allows designers to focus their attention on designing the behavior of a system and not spend as much time performing the formal logic synthesis steps as in the classical digital design approach. The goal of this chapter is to provide the background and context of the modern digital design flow using an HDL-based approach.

There are two dominant hardware description languages in use today. They are VHDL and Verilog. VHDL stands for very high speed integrated circuithardwaredescriptionlanguage. Verilog is not an acronym but rather a trade name. The use of these two HDLs is split nearly equally within the digital design industry. Once one language is learned, it is simple to learn the other language, so the choice of the HDL to learn first is somewhat arbitrary. In this text, we will use VHDL to learn the concepts of an HDL. VHDL is stricter in its syntax and typecasting than Verilog, so it is a good platform for beginners as it provides more of a scaffold for the description of circuits. This helps avoid some of the common pitfalls that beginners typically encounter. The goal of this chapter is to provide the background and context of the modern digital design flow using an HDL-based approach.

The invention of the integrated circuit is most commonly credited to two individuals who filed patents on different variations of the same basic concept within 6 months of each other in 1959. Jack Kilby filed the first patent on the integrated circuit in February of 1959 titled Miniaturized Electronic Circuits while working for Texas Instruments. Robert Noyce was the second to file a patent on the integrated circuit in July of 1959 titled Semiconductor Device and Lead Structure while at a company he cofounded called Fairchild Semiconductor. Kilby went on to win the Nobel Prize in Physics in 2000 for his invention, while Noyce went on to cofound Intel Corporation in 1968 with Gordon Moore. In 1971, Intel introduced the first single-chip microprocessor using integrated circuit technology, the