Asynchronous VLSI Design: An overview

An asynchronous circuit, or self-timed circuit, is a sequential digital logic circuit which is not enabled by a global clock signal. Instead of that, they often use signals that indicate completion of operations and instructions, specified by handshaking or simple data transfer protocols. This type is contrasted with a synchronous logic circuit where changes to the output signal values are triggered by clock signal. Most of the digital devices today are using synchronous logic circuits. But future Nano CMOS VLSI Technology will not be compatible with synchronous designs as Variations in physical parameters affect timing. These increased timing variations will reduce robustness and performance. However asynchronous circuit designs have the potential to be faster, less power consumption, lowering electromagnetic interference, with modular designs in large systems (SoCs). Keywords— Asynchronous Design, GALS Globally Asynchronous Locally Synchronous, Isochronic Forks, QDI Quasi Delay Insensitive Logic, Handshake Protocol