Duplex communication control device

A duplex communication control device for transmitting and receiving data among a plurality of communication stations connected to a communication network by passing a token therebetween, each of said plurality of communication stations comprising

• carrier detecting means for detecting a carrier on said communication network;
• token frame generating means for transmitting a token frame over said communication network when a token is received and said carrier detecting means detects no carrier for a given period of time while said token is held by said token frame generating means;
• collision detecting means for outputting an output signal indicating a collision when a frame from another communication station is received after transmission of said token frame;
• and
• wherein when said collision detecting means detects a collision or when said carrier detecting means detects a carrier within a given period of time, the token held by the station is abandoned and the station enters a reception state.

A duplex communication control system comprising

• at least two communication stations, each comprising a communication control device and a central processing unit connected to a communication network;
• wherein said system controls said at least two communication stations so that one communication station is used as a controlling station and the other is used as a standby station according to two signals having a mutually exclusive relation to each other and used for duplex control;
• said communication control device comprising a transmission-reception control means for controlling token passing transmission of data, and a loop back diagnosing means disposed in said transmission reception control means for executing a loop back diagnosis under instruction from said central processing unit;
• said central processing unit comprising a counter which is started at the beginning of said loop back diagnosis and reset at the end of said loop back diagnosis, and a time setting means for setting said counter at different counter values, depending on whether a station is used as a controlling station or as a standby station;
• and
• wherein when said counter runs out, said communication control device is judged to have a fault, and if such fault occurs in a controlling station, signal for duplex control are inverted.

A communication control device comprising a plurality of communication stations, each having respective addresses, said plurality of communication stations being connected via a bus, said communication control device executing communication by passing a token among said plurality of communication stations according to information bout said respective addresses;

• each of said plurality of communication stations comprising
• token-to-itself detecting means for detecting reception of a token addressed to a communication station containing said token-to-itself detecting means;
• monitor timer means which is set to a given time longer than the sum of the transmission delay time and the response delay time, for detecting reception of a token addressed to said station and for then measuring time after such detection;
• reception decision means for deciding whether a frame from another station is received before the time set in said monitor time means runs out;
• and
• wherein when a frame is received before said time in said monitor timer runs out, said reception decision means determines that a double address error has occurred, and said station is then disconnected from said bus.

A communication control device comprising a plurality of communication stations each having assigned thereto a respective address, said plurality of communication stations being connected via a communication network, said communication control device executing communication by passing a token between said plurality of communication stations according to information about said respective addresses;

• each of said plurality of communication stations comprising
• token-to-itself detecting means for detecting reception of a token addressed to its corresponding station;
• multiple master detecting means for transmitting a frame when said token-to-itself detecting means receives a token addressed to said corresponding station, and then for detecting a collision of frames on said communication network to thereby detect a multiple master condition;
• and
• collision number counting means for counting the number of detections of multiple master conditions and for instructing the corresponding station to disconnect itself from said communication network.

A duplex communication control device for transmitting and receiving data among a plurality of communication stations by passing a token between said plurality of communication stations connected to a first communication line and a second communication line, each of said plurality of communication stations comprising

• bus status list means for storing information indicating whether a station can communicate over said first and second communication lines;
• token generating means for carrying a newest bus status information on a token frame and for outputting said token frame for transmission over said first and second communication lines;
• list updating means for receiving said token frame transmitted over said first and second communication lines and for updating contents of a bus status list according to the bus status information carried on said token frame;
• and
• transmission-reception means for selecting one of said first and second communication lines for communication according to said bus status list;
• wherein
• said transmission-reception means selects a predetermined one of said first and second communication lines for communication when said bus status information contained in said bus status list indicates that both said first and second communication lines can be utilized.

A duplex communication control device for transmitting and receiving data among a plurality of communication stations by passing a token between said plurality of communication stations connected to a first communication line and a second communication line, each of said plurality of communication stations comprising

• bus status list means for storing information indicating whether a station can communicate over said first and second communication lines;
• token generating means for carrying a newest bus status information on a token frame and for outputting said token frame for transmission over said first and second communication lines;
• list updating means for receiving said token frame transmitted over said first and second communication lines and for updating contents of a bus status list according to the bus status information carried on said token frame;
• and
• transmission-reception means for selecting one of said first and second communication lines for communication according to said bus status list;
• wherein
• said transmission-reception means selects alternately said first and second communication lines for communication when said bus status information contained in said bus status list indicates that both said first and second communication lines can be utilized.

A duplex communication control device for transmitting and receiving data among a plurality of communication stations by passing a token between said plurality of communication stations connected to a first communication line and a second communication line, each of said plurality of communication stations comprising

• bus status list means for storing information indicating whether a station can communicate over said first and second communication lines;
• token generating means for carrying a newest bus status information on a token frame and for outputting said token frame for transmission over said first and second communication lines;
• list updating means for receiving said token frame transmitted over said first and second communication lines and for updating contents of a bus status list according to the bus status information carried on said token frame;
• and
• transmission-reception means for selecting one of said first and second communication lines for communication according to said bus status list;
• wherein
• each of said plurality of communication stations comprises transmission control means for providing control of token passing communication using a duplex communication network;
• and a processor unit coupled to said transmission control means via an internal bus;
• and wherein said transmission control means processes communication independently of said processor unit when a token is passed to a communication station and that communication station receiving the token or other stations request communication.

A duplex communication control device for transmitting and receiving data among a plurality of communication stations by passing a token between said plurality of communication stations connected to a first communication line and a second communication line, each of said plurality of communication stations comprising

• bus status list means for storing information indicating whether a station can communicate over said first and second communication lines;
• token generating means for carrying a newest bus status information on a token frame and for outputting said token frame for transmission over said first and second communication lines;
• list updating means for receiving said token frame transmitted over said first and second communication lines and for updating contents of a bus status list according to the bus status information carried on said token frame;
• and
• transmission-reception means for selecting one of said first and second communication lines for communication according to said bus status list;
• wherein
• each of said plurality of communication stations comprises diagnostic token generating means for carrying a diagnostic token on a newest bus status information and for transmitting said diagnostic token, said diagnostic token being used to cause a new communication station to be connected to said first and second communication lines to participated in communication;
• and wherein said list updating means updates contents of its own bus status list according to said bus status information carried on a diagnostic token frame provided upon receipt of said diagnostic token.