Patent ID: 8347009

Claim:
A communication system configured by connecting a plurality of communication nodes to a communication bus, the communication nodes being able to detect data transmitted to the communication bus, wherein: one communication node among the plurality of communication nodes, predetermined as a master node, comprises: reference transmitting means for repeatedly transmitting a reference message to other communication nodes to request transmission of their data, and one or more communication nodes among the plurality of communication nodes, predetermined as specific nodes, wherein each specific node comprises: priority transmitting means for transmitting, to the communication bus, priority information of transmission data to be transmitted currently from that specific node upon reception of the reference message transmitted from the master node, the priority information being indicative of priority of the transmission data for that specific node; priority detecting means for detecting whether the priority information transmitted from the other communication nodes indicates higher priority than the priority information transmitted by itself; data transmitting means for, if the priority information indicative of higher priority than the priority information transmitted by itself is not detected by the priority detecting means, transmitting the transmission data to the communication bus, and stopping transmission of data of the same priority as the priority of the data transmitted by itself until a next instance of the reference message is received; and priority retransmitting means for, if the priority information indicative of higher priority than the priority information transmitted by itself is detected by the priority detecting means, allowing the priority transmitting means to retransmit the priority information during a period of time of waiting for reception of the next reference message, after transmission data is transmitted to the communication bus from another communication node to which the priority information detected by the priority detecting means corresponds.