In: Proc. 2nd Workshop on Hardware Design and Petri Nets (HWPN'99) of the 20th Int. Conf. on Application and Theory of Petri Nets (PN'99), 21 June 1999, Williamsburg, VA, pages 149-168. 1999.
Abstract: A survey of known asynchronous behavior revealed additional causal relations (dependences) between input and output edges of asynchronous circuits besides the conventional relations of dependence, independence, and exclusion; two kinds of pseudo-causality, b- and tcb-concurrency (needed for signal-tracking behavior), causal linkage (for multiple input changes), and race causality (in critical input races). For their Petri net representation, several elements besides the conventional signal transition graph (STG) are needed; labeled read and inhibitor arcs, transitions labeled with joint events, and decision transitions for modeling asymmetric races. Based on these results, a generalized STG (gSTG) is defined and a brief sketch is given on how to derive circuits from it. On account of its comprehensive causal modeling power, it is proposed that this gSTG be used as the unified design entry of a comprehensive design style that enables the designer to chose the appropriate synthesis method and derive his design by appropriate transformations of the gSTG specification.
Keywords: Petri nets, asynchronous circuits, causal specifications, generalized signal transition graphs.
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