A Method for Synthesizing Sequential Circuits

The theoretical basis of sequential circuit synthesis is developed, with 'particular reference to the work of D. A. Huffman and E. F. Moore. A new method of synthesis is developed which emphasizes formal procedures rather than the more familiar intuitive ones. Familiarity is assumed with the use of switching algebra in the synthesis of combinational circuits. CONTENTS 1. Introduction 1.1 Foreword 1.2 Introductory Remarks 2. A Model for Sequential Circuits 2.1 The Model 2.2 State Diagrams 3. Circuit Equivalence 3.1 Moore's Theory 3.2 First Reduction Process 4. Development of the Method for Synchronous Circuits 4.1 Introductory Remarks 4.2 Modification of First Reduction Process 4.3 Second Reduction Process 4.4 Blank Entries; Uniqueness of Reduction 4.5 Final Remarks; Summary of Method 5. The Method Applied to Asynchronous Circuits 5.1 Introductory Remarks 5.2 Interpretation of the Model 5.3 Race Conditions; Coding of States 5.4 Huffman's Method 5.5 Summary of Method 6. Discussion 7. Acknowledgements 8. Selected Bibliography 1. I N T R O D U C T I O N 1045 1045 1046 1049 1049 1051 1053 1053 1056 1059 1059 1062 1063 1065 1065 1067 1067 1067 1069 1072 1072 1077 1078 1078 l.i Foreword T h e designer of a sequential switching circuit -- a circuit w i t h storage or " m e m o r y " -- faces a far more difficult problem t h a n is faced by the 1045 1046 THE B E L L SYSTEM T E C H N I C A L J O U R N A L , S E P T E M B E R 1955 designer of, say, a simple translating circuit. In the latter case, comparatively simple a n d straightforward m e t h o d s of synthesis are known.