A generalized signal transition graph model for specification of complex interfaces

This paper introduces a new Generalized Signal Transition Graph model for specifying complex mixed asynchronous/synchronous circuits, as found in system-level interfaces. The goal has been to develop extensions that make it possible to model mixed asynchronous/synchronous and arbitration behavior. A number of key extensions have been developed that makes the model much more widely applicable to industrial designs. The extensions include Boolean guards, the introduction of level semantics that make it possible to describe “events” in terms of both signal transitions as well as “signal levels”, and the semantic extensions for describing don´t care and undefined behavior. The latter extensions make it possible to model synchronous finite state machines using an asynchronous model, hence permitting the specification of mixed asynchronous/synchronous behavior. The proposed Generalized Signal Transition Graph Model is free from the restrictions of the previous models such as liveness, safeness, and free-choice requirements, and permits general Petri-net structures that may include multiple tokens in a place as long as the resulting state graph is bounded and has a consistent state assignment. A key aspect of the generalizations is that all the extensions are defined at the state graph level