Computer hardware has experienced the most dramatic improvement in capabilities and costs ever known to humankind. In just 40 years, we have seen room-sized computers, with little more processing power than today's pocket calculators, evolve into fingernail-sized devices with near supercomputer performance. This miracle has been made possible through advances in digital hardware, which now pervades all aspects of our lives. Just think how the lowly rotary telephone has become the cordless, automated answering machine. It can digitize your greeting, remember your most frequently dialed numbers, and allow you to review, save, and erase your phone messages.
This book will teach you the fundamental techniques for designing and implementing complex systems. A system has inputs and outputs and exhibits explicit behavior, characterized by functions that translate the inputs into new outputs. Design is the process by which incomplete and inexact requirements and specifications, describing the purpose and function of an object, are made precise. Implementation uses this precise description to create a physical product. You can see design and implementation in everything around you-buildings, cars, telephones, furniture, and so on.
This book is about the fundamental techniques used to design and implement what we call synchronous digital hardware systems. What does each of these words mean? A hardware system is one whose physical components are constructed from electronic building blocks, rather than wood, plastic, or steel. A hardware system can be digital or analog. The inputs and outputs of a digital system fall within a discrete, finite set of values. In an analog system, the outputs span a continuous range. In this book, we concentrate on systems in the digital domain. A synchronous system is one whose elements change their values only at certain specified times. An asynchronous system has outputs that can change at any time. It is safer and more foolproof to build our systems using synchronous methods, which is the focus of this book.