Composable specifications for asynchronous systems using UNITY

Using UNITY as a model for asynchronous hardware systems, we give a generic specification of a device that obeys a four phase protocol. The specification is general enough to allow devices with bundled data as well as dual-rail coded ports, and two phase signalling can be seen as a special case. We give a generic implementation of a function cell and show that A. Martin's Adder cell is an instance. Finally, we prove two composition theorems that allow four phase devices to be combined into larger four phase devices. All stated theorems were checked using a mechanical theorem prover and we give complete definitions for all the concepts used in the generic specification