Asynchronous propagation-limited logic

Abstract

It is generally recognized that asynchronous operation of logic networks offers specific advantages over synchronous operation controlled by a central clock when the network is subject to large or widely varying inter-module propagation delays. In this paper we characterize several previously described techniques for achieving asynchronous operation by a single model. Essential to the model is the bi-directional exchange of control information to control a one-directional data flow. A second important concept is that of detecting the completion of logical operations. The model readily generalizes to permit the control of modules that are sequential machines of arbitrary complexity. As a vehicle to demonstrate several characteristics of asynchronous networks, the design of a modular, asynchronous multiplier is described. One of its characteristics, termed "self-steering," entails the use of special symbols on the data paths to control dynamic reconfiguration of the network. Another characteristic, "flow mode" operation, is exemplified by the apparent flow of activity through the network. At, any given time, portions of several independent multiplication processes can be flowing through different portions of the network.