88.

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One machine can do the work of fifty ordinary men; no machine can do the work of one extraordinary man.

-E. Hubbard

Nothing dignifies labor so much as the saving of it.

-J. Rodgers

Introduction

In this chapter we begin our examination of the most important kind of sequential circuit: the finite state machine. Finite state machines are so named because the sequential logic that implements them can be in only a fixed number of possible states. The counters of Chapter 7 are rather simple finite state machines. Their outputs and states are identical, and there is no choice of the sequence in which states are visited.

More generally, the outputs and next state of a finite state machine are combinational logic functions of their inputs and present state. The choice of next state can depend on the value of an input, leading to more complex behavior than that of counters. Finite state machines are critical for realizing the control and decision-making logic in digital -systems.

In this and the following chapter we extend the counter design procedure of Chapter 7 to the more general case of finite state machines. In this chapter, we shall emphasize:

• Methods for describing the behavior of finite state machines. These include abstract state machine notation, state diagrams, state tables, and hardware description languages.
  
  
• Techniques for mapping word specifications into more formal descriptions of finite state machine behavior. We will examine four representative finite state machine design problems to illustrate the techniques for performing these mappings.
  

Table of Contents

1. The Concept of the State Machine
2. Basic Design Approach
3. Alternative State Machine Representations
4. Moore and Mealy Machine Design Procedure
5. Finite State Machine Word Problems
Chapter Review
Exercises

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This file last updated on 07/14/96 at 21:28:46.
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