25 September 2020

Difference between Synchronous and Asynchronous Sequential Circuits

The sequential circuit is one of the major categories of digital logic circuits. Based on the clock input, it is further classified into synchronous circuits and asynchronous circuits. So here this article gives the main comparison between a synchronous and asynchronous sequential circuit to better understand this topic.

Difference between synchronous and  asynchronous sequential circuit:

  • The synchronous sequential circuit is a digital sequential circuit in which the feedback to the input for the next output generation is governed by clock signals, while in the asynchronous sequential circuit are a digital sequential circuit in which the feedback to the input for the next output generation is not governed by the clock signals.
  • In a Synchronous sequential circuit, the memory unit which is being got used for governance is clocked flip flop, on the other hand, unlocked flip flop or time delay is used as a memory element in case of an asynchronous sequential circuit.
  • The states of Synchronous sequential circuits are always predictable and thus reliable, while in the hand there are chances for the asynchronous sequential circuit to enter into a wrong state because of the time difference between the arrival of inputs. This is called race conditions.
  • The synchronous circuit is used in counter, shift register, and memory units, while in the asynchronous sequential circuit are used in low power and high-speed operations such as simple microprocessors, digital signal processing systems, and communication system for an email application, internet access, and networking.
  • Synchronous sequential circuit is easy to design, on the other hand, the presence of feedback among logic gates causes instability issues making the design of asynchronous sequential circuit.
  • Due to the propagation delay of a clock signal in reaching all elements of the circuits the synchronous sequential circuits are slower in its operating speed. While in asynchronous sequential circuits since there are no clock signals, these are fast compared to the synchronous sequential circuits.