Asynchronous design of a router

A case study in asynchronous circuit design is undertaken. The design we present is particularly robust because the circuit will always function correctly, no matter what the delays in its elements and wires, The problem we consider is that of designing a general-purpose message router for Trans puters. First, a simplified version of a message router is specified. The specification is then taken through two levels of design. It is shown that identical switching elements can be connected together in a regular way so as to implement a router of arbitrary size. The specification and design are presented in a new CSP-like algebraic formalism that is especially suitable for dealing with delay-insensitive circuits. The formalism has three significant advantages over other approaches. The behaviour of circuits can be expressed in a concise, yet easily understood way. Errors arising from transmission interference of signals along wires are handled automatically. The result of connecting circuits together to form more complex circuits can be calculated by a process of algebraic transformation, achieving abstraction from communication on internal wires.