A Brief Overview of Automotive Buses

CAN (Controller Area Network)

Brief Description: Can bus is a serial bus originally developed by Robert Bosch GmbH in 1986 for in-vehicle networks in cars. CAN buses employing twisted wire pairs were specifically designed to be robust in electromagnetically noisy environments. The applications of CAN bus in automobiles include window and seat operation (low speed), engine management (high speed), brake control (high speed) and many other systems. CAN buses can also be found in other embedded control applications such as factory automation, building automation, and aerospace systems.

Maximum Data Rates: 1Mbps at 40m, 125Kbps at 500m, 50kbps at 1000m
Circuit Type: Differential
Physical Layer: Twisted Wire Pair, 9 pin D-Sub
Transmission Format: Asynchronous
Drive Voltage: High: 2.75v ~ 4.5v; Low: 0.5v ~ 2.25v; Differential: 1.5v ~ 3.0v
Network Topology: Point to Point
Standards: ISO 11898/11519
More Information: http://www.interfacebus.com/Design_Connector_CAN.html

LIN (Local Interconnect Network)

Brief Description: LIN specifications are developed by the LIN consortium. Version 1.1 was released in 1999. The current version is 2.0. A primary advantage of this bus is that it can be implemented with a single wire (using the vehicle chassis as a current return path). A small and relatively slow in-vehicle communication and networking serial bus system, LIN bus is used to integrate intelligent sensors and actuators. LIN can also communicate over a vehicle's power distribution system with a DC-LIN transceiver.

Maximum Data Rates: 19.2Kbaud at 40m
Physical Layer: Single-Wire Implementation
Transmission Format: SCI (UART) Data Format
Operating Voltage: 12v over a Single Wire
Network Topology: Single Master / Multiple Slave (Up to 16 slaves)
Standards: Enhanced ISO 9141
More Information:
http://www.interfacebus.com/Design_Connector_LIN_Bus.html
http://www.lin-subbus.org/

FlexRay

Brief Description: FlexRay is a high-speed serial communication bus for in-vehicle networks. It is an extended protocol version of byteflight. The extended FlexRay has the performance features required for active safety, such as redundant transmission channels and a fault-tolerant synchronization mechanism. Applications for FlexRay include steer-by-wire and brake-by-wire systems.

Maximum Data Rates: 500 kbps ~ 10 Mbps
Communication Modes:Time-triggered, Event-triggered
Network Topology: Single-channel topologies, Dual-channel topologies
More Information: http://www.flexray.com

MOST (Media Oriented Systems Transport)

Brief Description: MOST was originally designed by Oasis SiliconSystems AG (now SMSC) in cooperation with BMW, Becker Radio, and DaimlerChrysler for multimedia applications in the automotive environment.  It was intended to be implemented on an optical fiber, so the bit rates of this bus system are much higher than previous automotive bus technologies. Since 1997, seventeen international automotive manufacturers and more than fifty key component suppliers including automotive electrical suppliers and audio-video manufacturers have contributed to this technology. MOST buses provide an optical solution for automotive peripherals like car radios, CD and DVD players, and GPS navigation systems.

Maximum Data Rates: 23 Mbaud
Layers: All Seven Layers of the ISO/OSI Reference Model for Data Communication
Network Topology: Point to Point via a Ring Topology but Star Configurations
Other Feature: Plug and Play; 60 Channels, 15 MPEG1 Channels for user configuration
Standards: ISO 7498-1 (OSI Model)
More Information:
http://www.mostcooperation.com/home/
http://www.telos.de/most/
http://www.answers.com/Media%20Oriented%20Systems%20Transport


Source: http://www.cvel.clemson.edu/auto/auto_buses01.html