Multi-station token pass communication system and method

Abstract

A data communications system is disclosed which uses a passive communications medium such as coaxial cable for communication between multiple stations connected to the bus. A token concept is employed such that when the token is owned by a station, it allows that station to transmit high level messages over the bus and to command, if desired, other stations to transmit high level messages to it. The communications system is primarily masterless with each station capable of token ownership using the same set of rules to determine the circumstances when perceived events by the station cause that station to change state. Improvements are presented in the initialization of a token list, the addition of stations to an existing token list, duplicate station address protection through random numbers associated with each station, power down patch out of a station from the token list, the joining of two networks (two token lists), timer period randomization, and the use of redundant communication mediums.