Multiplex Communication System

System Diagram:

System Diagram (Part 2):

System Diagram (Part 3):

System Diagram (Part 4):

System Diagram (Part 5):

System Diagram (Part 6):

SYSTEM DESCRIPTION

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.




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.




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




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.

CONSTRUCTION AND OPERATION SYSTEM DESCRIPTION







1. GENERAL
The vehicle ECUs on the BEAN on the control the systems described.




2. GATEWAY ECU
The network gateway ECU's function to relay the signals that are exchanged among the buses (Door Bus, Instrument Panel Bus, and Light Bus), the AVC-LAN, and the diagnosis system. It carries out an integrated management of these communication functions.
If a malfunction occurs in BEAN communication, DTCs (Diagnostic Trouble Codes) are stored in its memory.




3. FAIL-SAFE
- Even if a malfunction occurs in another bus or in the network gateway ECU, the basis controls within the same bas will still function.
- Because the communication line of the BEAN forms a loop, communication remains intact even if an open circuit occurs in one area.
- To protect lighting operations when a malfunction disrupts communication, a back-up bus is provided.
- To ensure low-beam headlight and wiper HI operations, a fail-safe line is provided.

4. SELF-DIAGNOSIS
- If a malfunction occurs in the BEAN communication, the network gateway ECU stores DTCs in its memory.
- The DTCs can be read by connecting a hand-held tester to the DLC3.
- The Active Test can be performed and the Data List can be monitored by connecting a hand-held tester to the DLC3 and establishing communication with the network gateway ECU.