Abstract: A communication network, such as an audiovisual system, on an automobile has a master unit and a plurality of slave units which are connected to a common communication bus. The display unit displays operation of the other slave units based on display data transmitted from the other slave units. The display data includes character data regarding a character to be displayed and/or standard bit data common with the slave units. The character data and/or the standard bit data may be positioned at the leading end of the display data.

Abstract: A communication network, such as an audiovisual system, on an automobile has a master unit and a plurality of slave units which are connected to a common communication bus. When the communication network starts operating, connection confirmation request information is transmitted from the slave units to the master unit. The master unit awaits connection confirmation request information from at least one of the slave units for a predetermined period of time after the communication network starts operating. Thereafter, the predetermined period of time is extended if the reception of connection confirmation request information from all the slave units that were connected when the connection network stopped operating in a preceding cycle is not completed. If reception acknowledgement information from the master unit is not detected for a predetermined period of time, then the slave units automatically enter a low power consumption mode.

Abstract: A data communication system for use on a motor vehicle includes at least one master unit and at least one slave unit which are connected to a communication bus. When the master unit is enabled, the master controller of the master unit outputs connection request demand data to the slave unit. The slave unit has a slave controller which transmits its own connection request information to the master unit in response to the connection request demand data from the master unit. The slave controller transmits, to the master unit, first change information indicating whether the connection information stored in a first memory and connection information of the slave unit that has been transmitted to the master unit are identical to each other or not. The master controller transmits some or all of connection information stored in a second memory to slave units based on the first change information of the slave units.

Abstract: A communication network, such as an audiovisual system, on an automobile has a master unit and a plurality of slave units which are connected to a common communication bus. Each of the master and slave units is capable of successively issuing a plurality of command data through asynchronous transmission to another unit and returning acknowledgement data in response to the command data transmitted from another unit. The units add received command data to acknowledgement data when the acknowledgement data is to be returned. The command data includes first command data requiring acknowledgement data and second command data requiring no acknowledgement data. Each unit handles the first and second command data differently when the acknowledgement data is to be returned. When communication data is to be transmitted between the units, major classification data and subclassification data, depending on the contents of the communication data, are added to a leading portion of the communication data.