Interconnecting asynchronous control networks

The paper deals with the problem of obtaining an asynchronous control network through the combination of smaller ones, preserving some network properties. A control network is a set of interconnected circuits, each one performing an asynchronous sequential function. The operation speed of such a circuit is supposed to be unknown, and stray delays of arbitrary size are supposed to be present on the interconnection wires. An abstract model is utilized as a means of describing network behavior. Two network properties are considered, i.e., persistence (no signal is lost) and activity (there are no hang-up situations). Necessary and sufficient conditions are established to assure that a network, obtained by interconnecting smaller ones, is persistent and/or active.