The Bora car produced by FAW-Volkswagen Co., Ltd. was listed on December 9, 2001. The car incorporates many high-tech technologies, and two sets of CAN data transmission systems are installed in the powertrain and comfort system (Figure 1), this article will be introduced to this system.
1, CAN data transmission system overview
(1) why use the data bus
We know that the car between the two computers of information transmission, there are several signals to have a few signal transmission line (the signal transmission line can be used on the ground side of the public circuit), for example, Bora car engine electronic control unit J220 and automatic transmission control Unit J217 between the need for five signal transmission lines. If the transmission signal project also need more signal transmission line, this will lead to increase the number of electronic control unit pin, the line is complex, the failure rate increases and maintenance difficulties.
(2) what is the data bus
A car no matter how many pieces of electronic control unit, no matter how much information capacity, each electronic control unit only need to lead two lines common to the two nodes, the two wires called the data bus. In the past, there were many people riding a bike between the electronic control unit, and now these people take the bus, the bus can transport a large number of passengers, so the data bus also known as BUS line.
(3) what is the CAN protocol
Electronic computer network with electronic language to speak, the electronic control unit must use and interpret the same electronic language, this language called "agreement", car computer network, there are several common transmission protocols. Bora car with Bosch products, data bus using CAN protocol, this agreement is by Ford, Internet and Bosch company jointly developed high-speed automotive communication protocol. CAN is the abbreviation of ControllerAreaNetwork (control unit area network), which means that the control unit exchanges data through the network.
(4) CAN data transmission system advantages
Data bus and other components together to become a data transmission system, CAN data transmission system has the advantage of:
¢Ù the sensor signal line to a minimum, then more sensor signals for high-speed data transmission.
¢Ú electronic control unit and electronic control unit pin to minimize the application, saving the limited space of electronic control unit.
¢Û If the system needs to add new features, only software upgrades can be.
¢Ü monitoring of the electronic control unit on the CAN bus connected to real-time monitoring, such as failure of the electronic control unit will store the fault code.
¢Ý CAN data bus in line with international standards, in order to facilitate a car on different manufacturers of electronic control unit for data exchange.
2, CAN data transmission system structure and working principle
(1) CAN data transmission system
CAN data transmission system in each computer to add a CAN controller, a CAN transceiver; each computer connected to the external two CAN data bus. In the system as the terminal of the two computers, the internal also equipped with a data transmission terminal (sometimes the data transmission terminal installed outside the computer).
(5) the function of each component
¢ÙCAN controller role is to receive control unit in the microprocessor data, processing data and passed to the CAN transceiver. While the CAN controller also receives the data received by the transceiver, processes the data and passes it to the microprocessor.
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