Communication device, communication system and message arbitration method

A communication system in which a plurality of communication devices connected to a common communication line transmit and receive messages,

• each of the communication devices comprising:
• a processor;
• and
• a communication controller that includes a calculation unit that calculates as to a message to be transmitted a margin time before a time when a transmission of the message is to be completed, the margin time as being a time from a transmission start time of a message to a deadline time, a transmission unit that transmits the message to which information related to the margin time calculated by the calculation unit is attached, an arbitration unit that performs arbitration based on the information attached to the message when simultaneous message transmissions to the communication line occur and a storage unit that stores information related to a time when a message transmission is to be completed, and that transmits and receives a message to and from the communication line according to processing performed by the processor,
• wherein
• the processor writes information related to a time in the storage unit of the communication controller,
• the calculation unit, if a transmission request for a message is provided from the processor, reads the information related to the time from the storage unit and calculates the margin time based on a time point when the transmission request is provided and the information read from the storage unit, and
• as to a plurality of messages simultaneously transmitted to the communication line, the arbitration unit performs arbitration in such a manner as to prioritize a message with a shorter margin time.

A message arbitration method performing arbitration when simultaneous message transmissions by a plurality of communication devices connected to a common communication line occur, each of the communication devices comprising:

• a processor;
• and
• a communication controller that includes a calculation unit that calculates as to a message to be transmitted a margin time before a time when a transmission of the message is to be completed, the margin time as being a time from a transmission start time of a message to a deadline time, a transmission unit that transmits the message to which information related to the margin time calculated by the calculation unit is attached, an arbitration unit that performs arbitration based on the information attached to the message when simultaneous message transmissions to the communication line occur and a storage unit that stores information related to a time when a message transmission is to be completed, and that transmits and receives a message to and from the communication line according to processing performed by the processor,
• wherein
• the processor writes information related to a time in the storage unit of the communication controller,
• the calculation unit, if a transmission request for a message is provided from the processor, reads the information related to the time from the storage unit and calculates the margin time based on a time point when the transmission request is provided and the information read from the storage unit, and
• as to a plurality of messages simultaneously transmitted to the communication line, the arbitration unit performs arbitration in such a manner as to prioritize a message with a shorter margin time.