MULTIPLEX COMMUNICATION SYSTEM


  1. OUTLINE


    1. The multiplex communication system uses the following 2 communication protocols:


      1. The Controller Area Network (CAN) is used for communication between the engine, chassis, and body electrical system.

      2. The Local Interconnect Network (LIN) is used for communication within the body electrical system.

    2. The CAN has 2 types, with different communication speeds: the HS-CAN (high speed) and the MS-CAN (medium speed).

    3. The gateway function of the main body ECU, power management control ECU and headlight swivel ECU assembly convert signals that are exchanged between the CAN and LIN.

  2. MAIN FEATURES


    1. Multiplex communication uses serial communication data that consists of bits and frames in order to exchange information between the various ECUs. This allows a reduction of the amount of wiring on the vehicle.


      1. A bit is the basic unit of communication that is used to represent the information. A bit is represented by binary values of "0" or "1".

      2. A frame is a body of data that is transmitted together. A frame contains a header that indicates the beginning, and an end message that indicates the end.

        A0051OOE02

    2. Differences between CAN and LIN


      1. The protocols, which are the rules for establishing data communication, differ between the CAN and LIN. If the ECUs in the networks use different frameworks for their data, such as communication speed, communication wire, and signals, they will be unable to understand each other. Therefore, protocols (rules) must be established among them.

      2. Compared to the LIN, the CAN features high-speed data transmission. Therefore, the CAN is able to transmit larger amounts of data faster than other protocols. This feature makes it possible to transmit data accurately in the engine, chassis, and body electrical system, which requires large amounts of data to be transmitted in short periods of time.

        Protocol CAN (ISO Standard) LIN (LIN Consortium)
        Communication Speed

        500 kbps*/HS-CAN

        250 kbps*/MS-CAN

        (Max. 1 Mbps*)

        9.6 kbps*

        (Max. 20 kbps*)
        Communication Wire Twisted-pair Wire AV Single Wire
        Drive Type Differential Voltage Drive Single Wire Voltage Drive
        Data Length 1-8 Bytes (Variable) 2, 4, 8 Bytes (Variable)

        Tech Tips

        *: bps is an abbreviation for "Bits Per Second", indicating the number of bits that can be transmitted per second.

    3. Communication Wire


      1. A twisted-pair wire is used for CAN communication. A single, Automobile Vinyl (AV) wire is used for LIN communication.

        Communication Wire Outline
        Twisted-pair Wire A0051ZE This communication wire is a pair of twisted lines. Communication is driven by applying different voltages to the 2 lines in order to send a single signal. This system, which is called a "Differential Voltage Drive", reduces noise.
        AV Single Wire A00528U This is a lightweight single communication wire that consists of a single core line surrounded by insulation. Voltage is applied to this line in order to drive communication, and this system is called a "Single Wire Voltage Drive".
        A0051U5E02
        *1 AV Single Wire
        *2 Twisted-pair Wire
        *3 Single Wire Voltage Drive
        *4 Differential Voltage Drive