Digital System Clocking: High-Performance and Low-Power Aspects

PREFACE

Is it possible to write an entire book on the subject of clocked storage elements: latches and flip-flops? We certainly did not think so and we are sure many people today share this view. Indeed, this work started as a simple consulting project for Hitachi America Laboratories in the late 1990s that was not intended to last longer than six months. The objective was to examine several proposed and existing clocked storage elements and decide which one should be used in the new generation of microprocessors Hitachi had on the drawing board at that time. We finished this work, comparing several existing structures and recommending some improved solutions. However, the answers we provided raised many more questions and left us wondering. Now we feel that there are even more unanswered questions. Thus, we decided to collect our experience into a book and make it available to design engineers, practitioners, academics, managers, and anyone else interested in this aspect of high-performance and low-power digital system design.

Clocking is an important aspect and a centerpiece of digital system design. Not only does it have the highest positive impact on performance and power, but also the highest negative impact on the reliability of an improperly designed system. This is becoming more important, as the clock frequency keeps increasing dramatically as it has been in the last decade. The higher the frequency, the more important are the clock system and clock storage elements, because ...