What is an asynchronous circuit?
Asynchronous circuit is a network of mostly independent components that transmit data after completion of their operations. This is unlike the synchronous circuit where the elements are asked for data in response to the global timing signal. In the asynchronous circuit, data transmission protocols determine when and how the data is exchanged. Instead of regular interviewing each component, the data is transmitted when the component itself indicates that it is ready.
Most of the implementation of electronic circuits use synchronous design. It is a simpler model where all components work in the same time frame. In the asynchronous circuit, components work independently of any time frame. Instead of a discrete time stored globally, the components use the protocols of Handshake and Transfer. These perform the necessary synchronization, data transfer and sequencing.
In asynchronous circuits, several transmission protocols are used. All include a handshaking that ensures that when the component is readyTo pass the data to the neighbor, the neighbor is freely accepted and handled. Because the components work without a reference to the normal timeframe, the operations can be completed outside the sequence. The transfer protocol encodes the data created so that it can be assembled in the correct order.
Some early computers used asynchronous design. Illinois integrator and automatic computer, or Illiac I, developed by the University of Illinois in 1951, was such a design. However, rapid progress in integrated circuits technology required a basic design that was compatible with available sources. Synchronous design with system clock became the preferred approach.
The design of the asynchronous circuit has several potential advantages. Energy consumption would be much smaller with the removal of the timing circuit and there will be no need to power transistors that are not used. The operating speed would be determined by the real latencies between the components. INThe synchronous design is stored to suit the weakest element. The circuit intended for operation in asynchronous logic would usually be less influenced by mild changes of parts of the components as a result of the production process.
The disadvantages of the design of the asynchronous circuit stems mainly from the complexity. The number of necessary elements may be much greater than the number needed for the synchronous circuit. There are few tools for designing a computer (CAD) for the design of an asynchronous circuit. These circuits are also much harder to tune and solve problems than conventional proposals. Other overheads of hardware and implementation problems can compensate for profits in energy consumption and efficiency.