Quasi-Delay-Insensitive Return-to-One Design

Asynchronous design techniques are gaining attention in the scientific community for their ability to cope with current techneologies’ problems that the synchronous paradigm may fail to cope with. The quasi-delay-insensitive (QDI) design style [1] [2] is attractive to asynchronous circuits, especially because it allows wire and gate delays to be ignored given that isochronic fork [1] delay assumptions are respected. This reduces design complexity and eases timing closure and analysis. Defining a QDI template requires choosing a handshake protocol and a delay-insensitive (DI) code for data [2]. Here, absence of data (a spacer) can be signaled by setting all wires of a data channel to 0, defining the return-to-zero (RTZ) protocol. The RTZ protocol is well accepted in the research community, but tradeoffs of alternative manners for representing a spacer received little attention. An obvious alternative is the return-to-one (RTO) protocol, where a spacer is encoded by all data wires in a channel at 1 [3].