A.V. Yakovlev
A.I. Petrov
University of Newcastle upon Tyne. 1992
Signal Transition Graph (STG), the interpretation of Petri Net (PN) by the changes of values of binary signals, has recently become popular as a model for asynchronous control circuit synthesis. It is however unable to define the behaviour of abstract Asynchronous Control Structures (ACSs), whose components have many outputs and "signals" are multi-valued or symbolic. Our aim is to present a model, called Symbolic Signal Transition Graph (SSTG), that is the natural extension of STG in which PN transitions are labelled with the changes of values of symbolic variables. We present a synthesis procedure and sufficient conditions for the implementability of the binary expansion (after an appropriate encoding) of an SSTG specification of an abstract ACS. Two circuit synthesis examples, a bus interface and a two-way pipeline channel, effectively illustrate the approach.