Bus-type local area network using a token-passing scheme

摘要

A communication system for a bus-type local area network (10), comprising a master station (1), and a plurality of normal stations (2...N). The master station is provided with a memory table for storing a status of each of the normal stations, and a control unit for inquiring each of the normal stations if it wishes to join a logical ring or not, and revising contents of the memory table according to a result of the polling, and each of the master station and the normal stations is provided with the function of passing a token representing a transmission priority to one of the stations adjoining thereto in the logical ring. Since the management and construction of the logical ring is performed only by the master station according to a polling system whereas the normal stations carry out only the passing of the token, the structure of the more numerous normal stations can be simplified and the overall cost of the LAN system can be thereby reduced.