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System Description: Notes

  1. SYSTEM OUTLINE 

    General 

    • A multiplex communication system establishes serial data communication by connecting the ECUs on a single communication line in order to exchange multiple pieces of information.
    • The adoption of a multiplex communication system significantly reduces the number of wiring harnesses as well as the number of sensors.
    • The types of multiplex communication systems are the BEAN (Body Electronics Area Network), which consists primarily of the ECUs that control the body systems, and the AVC-LAN (Audio Visual Communication - Local Area Network), which consists of the ECUs that control the audio and visual systems.
      Fig 1: Conceptual Drawing Of Multiplex Communication System Diagram
      G02957467Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    Daisy Chain 

    • The ECUs that comprise that BEAN are connected serially in the shape of a ring. This type of connection method is called a daisy chain.
    • The ECUs are connected by a communication line, and multiple pieces of information are transmitted and received by the ECUs by slightly staggering their times.
      Fig 2: Identifying Daisy Chain
      G02957468Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    Communication Frame 

    The ECUs in the BEAN exchange data in the form of individual clusters called communication frames, which are configured as described in Fig 4.

    Fig 3: Identifying Communication Frame
    G02957469Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  2. GENERAL 
    • The BEAN consists of three buses (a signal cluster daisy chain):
      1. Door bus
      2. Instrument panel bus
      3. Light bus
    • The Gateway ECU connects the buses, AVC-LAN, and DLC3 (Data Link Connector 3), and manages the communication among them.
    • The communication between the control signals related to the audio and visual systems and the Gateway ECU is established via the AVC-LAN.
    • A customized body electronics system has been adopted. Some operational settings of this system can be changed using a hand-held tester to accommodate the user's needs.
    • To protect lighting and wiper operations when a malfunction disrupts communication a backup bus and fail-safe line is provided.
      Fig 4: Bean Instrument Panel Bus Flow Diagram
      G02957470Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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