Dr. Geoffrey Lawday currently holds the Tektronix Chair in Measurement at Buckinghamshire New University where he teaches embedded system design and high performance computing in the School of Computing. Having gained a BSc in Physics and an MSc in Computer Engineering at Surrey University, he was awarded a PhD in Time-Frequency Signal Analysis from Brunel University. His research in signal integrity engineering is reflected in his publications, such as the critique on the introduction of the new serial buses published in the flagship journal of the Institution of Electrical Engineers.
David Ireland has more than thirty years experience in test and measurement ranging from an engineering apprenticeship with Racal, where he gained his formal electronic engineering qualifications, to his current position at Tektronix, where he is the marketing manager of design and manufacturing at Tektronix Europe. He is widely recognized by embedded system engineers in Europe for his signal integrity articles and collaborative workshops on high-speed digital system design, test, and measurement.
Greg Edlund’s career in signal integrity began in 1988 at Supercomputer Systems, Inc., where he simulated and measured timing characteristics of bipolar embedded RAMs used in the computer’s vector registers. Since then, he has participated in the development and testing of nine other high-performance computing platforms for Cray Research, Inc., Digital Equipment Corp., and IBM Corp. He has had the good fortune of learning from many talented engineers while focusing his attention on modeling, simulation, and measurement of IO circuits and interconnect components. A solid physical foundation and practical engineering experience combine to form a valuable perspective on optimizing performance, reliability, and cost.
PrefacePreface
What This Book Is About
We live in the high-speed digital age where embedded system developers in many cases must apply new design methodologies and perform complex signal integrity tests and measurements. This book guides the reader through the full life cycle of embedded system design from specification and simulation to test and measurement. A significant feature of the book is the explanations of the thorny issues of signal integrity engineering that are so often the cause of delay in a product's development—time to market is the signal integrity engineer's Achilles' heel. By considering the whole life cycle from simulation through to test and validation you can see the new interplay of simulation and real-time test, which drives the new design methodologies. A case in point is the design and implementation of a new high-speed serial bus where the simulation and real-time test are inextricably linked, especially where designs incorporate device driver pre-emphasis or receiver equalization.
The celebrated teacher and philosopher Archimedes said, "What we must learn to do is to learn by doing," and this book endeavors to do just that by presenting practical applications so that you can learn from the authors' experiences in embedded system design, simulation, test, and measurement. What's more, you are encouraged to consider and adopt good practices in signal integrity engineering throughout the entire life cycle of the design.
Of particular importance today is the need to meet regulatory compliance and interoperability requirements. Consequently this book treats the demands of compliance testing and interoperability design as a foremost topic. Alongside today's compliance testing is the migration to high-speed serial buses, where both topics lend themselves to some prime examples of good practice in signal integrity engineering. Therefore, the design and testing of high-speed serial buses with their associated low-voltage differential signaling are pivotal themes throughout several chapters of this book. Nevertheless, the fundamentals of signal integrity engineering underpin the understanding of compliance testing and interoperability design, and you are encouraged to refresh or learn the basics of signal acquisition, test, measurement, and device simulation, which for the most part is provided in this book.
Work as a team has become routine for engineers designing, developing, and testing digital systems. The members of the team build up companionships and regularly look to each other for advice, especially in today's complex high-speed digital world. Today, the task of developing or testing a digital system is complex, and even the design of what appears to be a simple circuit can be problematic. For example, an engineer can design a simple digital circuit that meets all the requirements, and then a year down the line a chip is changed because the new chip is cheaper and has the same functionality. What the engineer didn't know is that the new chip is now made with a smaller device size that reduces its cost and its switching time, leading to faster edge rates and signal integrity problems! This leads to the well-documented quote "There are two kinds of design engineers, those that have signal integrity problems, and those that will." As we have seen if a design is sensitive to edge rates, the component specification must make edge rate a formal product parameter since it is just not possible to anticipate the evolution of a silicon fabrication process. This book aims to be a companion to the engineer and part of the engineer's team by providing an understanding of design specification, simulation, test, and measurement along with some significant advice on maintaining signal integrity throughout the life cycle of a design.
Although we can take the big view, there are significant little problems that the engineer needs to know but, as they say, "is afraid to ask." For example, if a designer suspects ground bounce, or more accurately transients in the signal reference, and wants to measure the ground line with an oscilloscope, where is the probe ground connected? Actually, it is normally connected to a solid logic zero. Moreover, why is it that a state-of-the-art oscilloscope can give a 50% measurement error when measuring ground bounce? Well, the bandwidth of an oscilloscope is typically specified at the –3 dB point, and a voltage measured at the limit of the specified oscilloscope bandwidth will be shown as half the real voltage. Also it is important to measure the voltage but think in terms of current—since the current spike on a ground rail generates crosstalk and spurious switching. And we could go on; there are a myriad of signal integrity challenges from intermittent setup and hold violations, resulting in problems ranging from metastability to electromagnetically induced crosstalk. The ability to foresee signal integrity problems and how to avoid them is fundamental to this book.
A feature of this book is the blend of source material. Whereas a theoretical text on signal integrity is built on scientific laws and notable hypotheses, this book has sourced its applications from the authors' professional experiences, published papers, and the work of associates. This book is a blend of source material coherently assembled and expanded to provide an understanding of modern signal integrity applications. Practical issues concern us most in this book. Each chapter focuses on a day-to-day activity of the signal integrity engineer, giving advice and illustrations from the industry. Practicality forms the central theme throughout the book.
The twenty-first century is a digital era of media convergence where mobile telephony, computing, and digital broadcasting merge, and consumers expect the media to be transparent to the technology. Put simply, the sports fan expects to view an event, in real time, on his or her mobile phone, laptop, and personal music player or digital TV at a reasonable cost and with absolute reliability. We could have taken any number of other examples from industry, medicine, or the military. Today, the digital designer or maintenance engineer is expected to be accomplished at signal integrity engineering, which is at the heart of the provision of systems that will make tomorrow's innovative technologies happen. This book reflects this trend.
The Intended Audience
Signal integrity engineering is a young and evolving science where few who proclaim to know it all. Writing this book has been a journey of discovery for the authors, and we have every reason to believe it will be a rewarding journey for you. We have no doubt that some topics discussed in this book will provoke debate as there is much to be standardized in this branch of engineering. However, indisputable principles are presented in this book that underlie signal integrity engineering. These principles give the emergent engineer a basis on which to build the knowledge and understanding necessary for good signal integrity engineering. Therefore, this book is recommended reading for the student signal integrity engineer and the practicing engineer whereby the authors present a wealth of applications that illustrate good practice and show the development, test, and validation of modern digital systems.
While the book is naturally partitioned into chapters of diverse topics a common thread runs throughout the book. Each chapter provides a guide for the reader by presenting the necessary prerequisites of a topic before detailing complex design or test applications. Consequently the experienced engineer can approach a topic by stepping through the beginning of a chapter and concentrating on the detail in the applications and advanced topics. No signal integrity book claims to be all encompassing, and this book is no exception. You may need to consolidate your understanding of the theory of signal integrity engineering via in-depth theoretical texts in the Prentice Hall SI series. Nevertheless, much of this book is self-contained in terms of addressing a wide audience in signal integrity engineering.
How This Book Is Organized
To guide you through the full life cycle of embedded system design, including specification, simulation, test, and measurement, the book is structured, where possible, chronologically to follow the development cycle. However to encompass the diverse aspects of signal integrity engineering and to provide a coherent thread as you read, chapter order is a compromise of product life cycle flow and a natural grouping of signal integrity engineering topics. Therefore both compliance and serial bus simulation are found toward the latter part of the book, whereas earlier topics are prerequisites for these more advanced subjects.
Chapter 1: Introduction: An Engineer's Companion
Chapter 1 takes you into the world of device and circuit simulation, which is a major phase in the successful development of a modern digital product. A thought-provoking example is given whereby a designer is under the intense pressure of time to market where it's easy to overlook a true understanding of operating margins—will a network continue to function reliably over the range of manufacturing and operating conditions it will encounter during the useful life of the product? What are the expected primary failure mechanisms, and how do they interact with one another? Some of these complex simulation questions will be considered in the body of the introduction, but more to the point, these discussions lead the way to the in-depth chapters that examine these concerns.
Following simulation, the introduction describes in detail a number of principal innovations in signal integrity engineering test and measurement. For example, to overcome some of the traditional signal integrity engineering problems, device manufacturers currently use novel integrated signal processing functions within device drivers and rec...
