Multiplex Communication System

System Diagram:

SYSTEM DESCRIPTION




1. BASIC OF MPX
General
The LEXUS LS430 multiplex communication uses serial communication, which converts multiple pieces of information into serial communication data. As a result, they can be transmitted through a single communication wire.




Serial communication data consists of bits and frames. A bit is the basic unit that represents the amount of information. A bit is represented by binary values "0" or "1". A frame is a body of data that is transmitted together. A frame contains a "header" that indicates the beginning of the data and an end message that indicates the "end" of the data.

Network Style
Based on serial communication, various ECUs are connected on a network to exchange various pieces of information. Such a system is called a multiplex communication system.




- The CAN uses the multi star style bus connection. The 3 junction connectors are connected with a main bus line. The junction connector extends a sub bus line and enables communication between all the connected ECUs.




- The BEAN uses the ring and bus styles of networks to connect ECUs. This style of connection method is called a daisy chain. In a daisy chain, communication can be maintained even if there is an area that has an open circuit.




- The AVC-LAN uses a star style, which is centered on the multi display or audio head unit.

Difference of CAN, BEAN and AVC-LAN

1. General




The protocols, which are the rules for establishing data communication, differ between the CAN, BEAN and the AVC-LAN. If ECUs use different types of 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.

1. Communication Wire







A single, Automobile Vinyl (AV) wire is used for BEAN communication. A twisted-pair wire is used for CAN and AVC-LAN communication.

2. GATEWAY ECU




General
The gateway ECU of the LEXUS LS430 has the following functions.