Tradeoffs Between RTO and RTZ in WCHB QDI Asynchronous Design

Matheus Moreira1,  Julian Pontes2,  Ney Calazans1


Classically, quasi-delay-insensitive asynchronous circuits based on weak-conditioned half-buffer employ the return-to-zero, 4-phase handshake protocol. This work scrutinizes the alternative return-to-one protocol and analyzes the effects of using it in practical circuits. A pipelined shift and add multiplier serves as case study. Return-to-one and return-to-zero versions of the circuit provide ground for extensive comparison. Experimental results point to reductions in static power and in forward propagation delay of up to 35% and 12%, respectively, when using return-to-one. Also, results indicate that mixing return-to-zero and return-to-one leads to dynamic power savings.