Patent ID: 7373577

Claim:
A controller area network (CAN) system comprising: a CAN bus; and a plurality of electric control units (ECUs) respectively connected to the CAN bus, at least one of the plurality of ECUs having: a protocol processing part that performs data format interpretation processing of receive data according to a CAN protocol, and performs data format preparation processing of send data according to the CAN protocol; a register that stores error data information on an attribute of error data; a message processing part that can retain receive message data contained in the receive data and send message data to be contained in the send data; and an error management circuit that can detect whether the receive data contains error data; the protocol processing part incorporating the error data into the receive data or the send data, based on the error data information, wherein the error data information contains instruction information indicating that a stuff bit should be again inverted to obtain the error data during stuff bit mode in which the stuff bit generated by inverting the data value is inserted into the send data when a plurality of bits continuously have the same data value, the protocol processing part has a send data control part that can prepare, in a data format of the send data, the send message data from the message processing part and, that receives the instruction information to again invert the stuff bit when a position of the preparation processing in the send data reaches the insert position of the stuff bit, and that inserts the inverted stuff bit into the send data, thereby incorporating the error data into the send data.