![]() They were studied more formally and applied to the design of asynchronous interfaces by Alex Yakovlev in 1982, in his PhD thesis (in Russian). STGs were first proposed in 1981, under the name Signal Graphs, by Leonid Rosenblum (in Russian) in. true concurrency) while in state graphs concurrency is represented via interleaving. In STGs concurrent events are represented via cause-sequence relations (cf. ![]() The complexity of an STG specification of a circuit is typically linear in the number of signals in the circuit while the complexity of a state graph can grow exponentially, due to the fact that asynchronous circuits have high degree of concurrency. STGs usually give more compact descriptions of the behaviour of asynchronous circuits than state graphs. For example, the typical case of the labelling is the case where signals are binary, hence the transition are interpreted as rising and falling edges of the signals in the circuit. More formally, an STG is a type of an interpreted (or labelled) Petri net whose transitions are labelled with the names of changes in the values of signals (cf. Block-diagram and timing diagrams (a) and the corresponding STGs (b).
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