Physical Characterization of Asynchronous Logic Library

Abstract

Neuromorphic electronic systems have used asynchronous logic combined with continuous-time analog circuits to emulate neurons, synapses, and learning algorithms. It is attractive because of its low power consumption and feasible implementation. Typically, the neuron firing rates are lower than the modern digital systems. Thus, the endpoints of neuromorphic electronic systems are clusters of neurons instead of individual neurons. Address event representation (AER) was proposed in 1991 to multiplex communication for a cluster of neurons into an individual communication channel. AER circuits provide multiplexing/demultiplexing functionality for spikes that are asynchronously generated by/delivered to an array of individual neurons. Asynchronous techniques are not only used in neuromorphic electronic systems, but also widely used in globally asynchronous and locally synchronous (GALS) SoCs, or SoCs with full-asynchronous solutions. However, commercial tools on the market do not support designing asynchronous circuits, making the circuits cannot be adopted easily by most products. This thesis aims at addressing the challenge by providing an asynchronous library establishment strategy. The strategy uses SR-latches as standard asynchronous cells together with logic gates to build an AER communication circuit. With the strategy, the performance of using a modified traditional arbiter in the AER transmitter can be compared favourably with using state-of-the-art arbiters. A back-end flow and a verification flow are developed to evaluate the performance of the design as well as to check the feasibility of the strategy. The proposed 32-bit AER transmitter under TSMC 28nm CMOS technology sacrifices area and power to achieve better timing performance, where the modified arbiter inside has an 11.54% better response time than the arbiter who used to be the best in an old comparison.