MULTIPLEX COMMUNICATION SYSTEM


  1. OUTLINE


    1. The multiplex communication system uses the following 4 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.

      3. The Audio Visual Communication-Local Area Network (AVC-LAN) is used for communication only between the Audio Visual (AV) system components.

      4. The Media Orientated System Transport (MOST) is used for communication within the Audio Visual (AV) system components.

    2. There are two types of CAN communication systems, with different communication speeds: the HS-CAN (high speed) and the MS-CAN (medium speed).

    3. The network gateway ECU and main body ECU are used as gateways to transmit data between the buses.

  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 used in the vehicle.


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

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

        B002FVHE02

    2. Differences between CAN, LIN, AVC-LAN and MOST


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

      2. Compared to LIN and AVC-LAN, CAN features high-speed data transmission. Therefore, CAN is able to transmit larger amounts of data faster than other protocols. This feature makes it possible to transmit data accurately for the powertrain and chassis control systems. These systems require large amounts of data to be transmitted in short periods of time.

      3. MOST is used to transmit control information, audio, video, and data in real time.

        Protocol CAN (ISO Standard) LIN (LIN Consortium) AVC-LAN MOST
        Communication Speed

        500 kbps*1/HS-CAN

        250 kbps*1/MS-CAN

        (Max. 1 Mbps*1)

        9.6 kbps*1

        19.2 kbps*1*2 (Max. 20 kbps*1)

        Max. 17.8 kbps*1/AVC-LAN

        7.5 Mbps*1/AVC-LAN plus

        		 Max. 50 Mbps*1
        Communication Wire Twisted-pair Wire AV Single Wire Twisted-pair Wire Shielded Twisted-pair Wire
        Drive Type Differential Voltage Drive Single Wire Voltage Drive Differential Voltage Drive
        Data Length 1-8 Bytes (Variable) 2, 4, 8 Bytes (Variable) 0-32 Byte(s) (Variable) 0-128 Byte (Variable)

        Tech Tips

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

        *2: Communication between the skid control ECU and ECM

    3. Communication Wire


      1. A twisted pair of wires is used for CAN and AVC-LAN communication. A single Automobile Vinyl (AV) wire is used for LIN communication.

        Communication Wire Outline
        Twisted-pair Wire B002FIA This communication wire is a pair of twisted wires. 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 B002FUH 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".
        Shielded Twisted-pair Wire B002FU8 This communication wire is a shielded pair of twisted wires. 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.
        B002F9SE02
        *1 AV Single Wire
        *2 Twisted-pair Wire
        *3 Single Wire Voltage Drive
        *4 Differential Voltage Drive