INTRODUCTION: THE IMPORTANCE OF SIGNAL INTEGRITY - Advanced Signal Integrity for High-Speed Digital Design - page 7

possible after the fact to locate the root cause. As timing becomes more con-
strained, the simplifications of the past are rapidly dwindling in utility to the
modern designer. In this topic we also show how to incorporate a large num-
ber of variables that would otherwise make the problem intractable. Without
a methodology for handling the large number of variables, a design ultimately
incorporates some guesswork, no matter how much the designer understands the
system physically. The final step in handling all the variables is often the most
difficult part and the one most readily ignored by designers. A designer crippled
by the inability to handle large numbers of variables will ultimately resort to
proving a few “point solutions” instead and hope that they plausibly represent
all known conditions. Although such methods are sometimes unavoidable, this
can be a dangerous guessing game. Of course, a certain amount of guesswork
is always present in design, but the goal of the system designer should be to
minimize uncertainty.
1.4 A NEW REALM OF BUS DESIGN
Technology has progressed to a point where digital design has entered a new
realm, where new design techniques and concepts are required that baffle even
the most seasoned digital system designers. The fact is that present and future
state-of-the-art digital systems, such as personal computers, cannot be designed
without a thorough understanding of the principles outlined in this topic. Why
hasn't this been a problem before? The answer is that digital designers didn't
need to understand these things. But digital circuits are reaching speeds where
design will not be possible without an understanding of this subject. Seasoned
engineers face the threat of becoming a legacy if they do not adapt to the new
design space. This topic will help practicing engineers adapt.
From the Monroe calculator to the Pentium, from punch cards to flash memory,
from vacuum tubes to integrated circuits, computer performance is increasing at
an exponential rate. In this topic we address the needs of the contemporary digital
designer as he or she encounters the numerous new challenges with modern and
future high-speed digital systems and is forced to learn material previously not
needed. As the conventional digital designer transitions to faster designs, he or
she will indeed experience a completely different view of logic signals at high
speeds. This topic will help to make sense of the ugly, distorted, and smeared
waveforms produced in a high-speed digital system.
1.5 SCOPE OF THE Topic
This topic was written to be an advanced study in signal integrity. Although some
basic material is covered, it is assumed that the reader is well acquainted with
basic electromagnetic theory, vector calculus, differential equations, statistics,
and transmission-line analysis. The topic builds on the traditional knowledge
base and covers topics required to design present and future digital systems.