General

GENERAL

LAN

- The LAN system*1 enables data sharing among computers, that otherwise are left to function as independent systems, by connecting them via communications lines.
- Introduction of the LAN*1 system has improved equipment and functions while reducing the weight of the vehicle by eliminating a considerable amount of harnesses.
- Data transmission/reception is via CAN*2, which offers high-speed communication and also ensures a high level of reliability.
- Depending on control requirements, two transmission rates are used: high-speed CAN running at 500 Kbps, which is an ISO 11898 and manages power-related units; and low-speed CAN running at 125 Kbps, which is an ISO 11519-2 and manages body-related functions.
- Networks running at different transmission rates usually cannot share data between them, however, the body integrated unit with a gateway (hookup) function enables data sharing between different- rate networks.

NOTE:
*1: LAN (Local Area Network). A system where multiple computers (units) are linked via serial communication for data sharing.
*2: CAN (Controller Area Network). A serial communications protocol in compliance with ISO 11898 and ISO 11519-2.

CAN

- CAN is a serial communications protocol in compliance with relevant ISO standards.
- With its high bit rates, CAN enables quick, large-volume data transmission/reception.
- Based on continuous change in bus level (logical signals: low "0" and high "1") stemming from voltage difference between CAN_High and CAN_Low, data and other frames are configured for message identification.
- If an error is detected, CAN's fault confinement feature prevents the error from impacting units.
- If an error is detected, an error frame (notification that an error has been detected) is sent to units, telling them not to perform control based on data including errors.
- Depending on the status of the error detected, transmission/reception of the relevant data will be aborted.

COMPARISON BETWEEN CAN AND CONVENTIONAL DATA COMMUNICATION

- With conventional data communication, each sensor relies on its dedicated wiring for message to be sent between units. As data volume grows, so does the volume of wiring.
- CAN uses only one twisted-pair cable to connect between units for shared communication.

Conventional Communication:

1. CONVENTIONAL COMMUNICATION

NOTE: Conventional data communication needs as many data transmission lines as sensors used. (parallel signals)

Can Communication:

2. CAN COMMUNICATION

NOTE:
- With CAN, one twisted-pair cable (2 wires) manages transmission of all data. (serial communication)
- The main wire runs between the terminal resistor on the ECM and that on the ABSCM or vehicle dynamics control (VDC) CM & H/U. Other units are connected, in parallel, to the main wire via branch wires.