Introduction

Introduction

• We have seen, in synchronous sequential circuits, memory elements are clocked flip-flops. In asynchronous sequential circuits, memory elements are either unclocked flip-flops or time delay elements. Therefore, in asynchronous sequential circuits change in input signals can affect memory element at any instant of time. In synchronous circuits, the designer has to consider the time delays involved to determine the maximum operating speed of the clock. In asynchronous circuits, clock is absent and state change occurs according to delay times of the logic. Due to this, asynchronous circuits are more difficult to design. However, because of absence of clock, asynchronous circuits are faster than synchronous circuits.

Review Questions

1. How does the operation of an asynchronous input differ from that of a synchronous input ?

AU : Dec.-05, Marks 2

2. What is an asynchronous sequential circuit ?

AU : Dec.-04, Marks 2