Asynchronous Sequential Circuits - Introduction

ASYNCHRONOUS SEQUENTIAL CIRCUITS – INTRODUCTION

·              Do not use clock pulses. The change of internal state occurs when there is a change in the input variable.

·              Their memory elements are either unclocked flip-flops or time-delay elements.

·              They often resemble combinational circuits with feedback.

·              Their synthesis is much more difficult than the synthesis of clocked synchronous sequential circuits.

·              They are used when speed of operation is important.

The communication of two units, with each unit having its own independent clock, must be done with asynchronous circuits.

The general structure of an asynchronous sequential circuit is as follows:

There are n input variables, m output variables, and k internal states.

Fundamental-mode operation assumes that the input signals change one at a time and only when the circuit is in a stable condition.