Page 643 - Engineering Digital Design

CHAPTER 13

Alternative Synchronous

FSM Architectures

and System-Level Design

13.1 INTRODUCTION

It is in this chapter that an attempt will be made to bring the subjects of Chapters 10 through
12 together in some meaningful fashion so that useful controller and system-level designs
can be created. This is, to state it mildly, no simple task, since an almost endless number of
alternatives are available to the designer. Accordingly, and without apology, the treatment
will be limited to a few select topics that are representative of some of the more popular and
constructive approaches to state machine and system-level design. The "creativity" aspect
of the design task is highly valued and should be exercised by the skilled designer whenever
it is profitable to do so. To a reasonable extent this creativity ethic will be used in this chapter,
but only if it serves to edify the reader's experience in design without unnecessary effort.
Cute or novel designs that add little or nothing to an understanding of design fundamentals
will be left to the reader's imagination.

13.1.1 Choice of Components to be Considered
The first thing that must done before proceeding is to list the various devices that should be
considered for use in a given design architecture. The various components available to the
designer are divided into the following five categories:

1. Next state and output-forming logic. Choose from the following:

Discrete logic (gates mainly)
MUXs
Decoders
ROMs
PLAs
Basic I/O PALs
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