Method and system for transmitting messages between several stations of a local industrial decentralized network with a deterministic token passing access protocol

摘要

Method and system for exchanging messages between several stations interconnected by a common support or medium (12). Each station possesses its own address, and access to the medium (12) is shared between the stations thanks to a token-passing deterministic protocol managed by a coupler (CR1 ... CRn) associated with each station. Means of shaping a collision signal ensure detection of a token duplication. Means of detecting an activity signal make it possible, after the lapsing of specified standby times, to determine implicit acknowledgement of the token, token loss and the algorithm for regenerating the token. The medium (12) is formed by a dual cable (lines L1 and L2), and active redundancy is continuously monitored by each coupler equipped with an automatic management unit (42) comprising a first and a second circuit (46, 48) for working out the state of the communication channel (V1, V2) and a circuit (50) for synthesising the preceding states and the elementary activity and collision signals for the two channels (V1, V2). IMAGE