CAN-bus is Controller Area Network, Germany BOSCH in the early 1980s to address the large number of Hyundai Motor in the control and test equipment and data exchange between the development of a serial data communications bus, is The world's most widely used one of the fieldbus. Its high reliability, high cost performance, adaptability good. Many foreign cars such as Mercedes-Benz, BMW, Volkswagen, Volvo, Renault and Pa Liao cars used CAN bus technology [3]. CAN communication protocol describe the main equipment of the transmission of information between the ways? Communication interface integrated CAN protocol physical layer and data link layer functionality, the communications data processing frame. It provided a guarantee for the car in this particular application of the environment.

(1) the reliability of data communication CAN bus every frame CRC information has seized the wrong calibration and other measures, with excellent results seized wrong, and CAN nodes in the case of a serious error has shut down automatically output, so that Bus operators on the other nodes will not be affected.
(2) real-time data communication CAN bus communication rate of 1 Mbps, in a newspaper article on the identifier, CAN nodes on the divided into different priority, high-priority data to the occupation of bus priority, priority High in the data up to 134 ms within the transmission.
(3) data communications flexibility CAN bus is a multi main bus architecture, each node between independence, on any bus can be a node at any moment own initiative to other nodes on the network send a message. The block-oriented data communication mode, each frame is 8 bytes of data, communications medium for the twisted-pair, coaxial cable or optical fiber. Since CAN communication protocol includes only the physical layer and data link layer that is not the function of the application layer and the achievement of defined, so users can use the international CAN bus users and manufacturers associations or other organizations to develop the open High-level agreements, can also project the kind of flexibility to realize their own application layer.

Trucks and buses communications standard SAE J1939 automotive applications will be the implementation of specific, uniform definition of a comprehensive set of address coding system so that different manufacturers controller (ECU) can access the same network system, data sharing, A decrease of the electronic system Harness, reducing redundant sensors, reducing costs, improving the system's versatility and reliability, while improving the flexibility of the system.