Controller Area Network CAN Bus I need to know why this netw

Controller Area Network (CAN Bus)

I need to know why this network is important in a car

How does CAN Network works in a Automobile. please give complete details about how the communication works.

Solution

There are four main applications for serial communication in vehicles, each having different requirements and objectives.

Using CAN, peer stations (controllers, sensors and actuators) are connected via a serial bus. The bus itself is a symmetric or asymmetric two wire circuit, which can be either screened or unscreened. The electrical parameters of the physical transmission are also specified in ISO 11898. Suitable bus driver chips are available from a number of manufacturers.

The CAN protocol, which corresponds to the data link layer in the ISO/OSI reference model, meets the real-time requirements of automotive applications. Unlike cable trees, the network protocol detects and corrects transmission errors caused by electromagnetic interference. Additional advantages of such a network are the easy configurability of the overall system and the possibility of central diagnosis.The purpose of using CAN in vehicles is to enable any station to communicate with any other without putting too great a load on the controller computer.

Principles of data exchange.

When data are transmitted by CAN, no stations are addressed, but instead, the content of the message (e.g. rpm or engine temperature) is designated by an identifier that is unique throughout the network. The identifier defines not only the content but also the priority of the message. This is important for bus allocation when several stations are competing for bus access.

If the CPU of a given station wishes to send a message to one or more stations, it passes the data to be transmitted and their identifiers to the assigned CAN chip (”Make ready”). This is all the CPU has to do to initiate data exchange. The message is constructed and transmitted by the CAN chip. As soon as the CAN chip receives the bus allocation (”Send Message”) all other stations on the CAN network become receivers of this message (”Receive Message”). Each station in the CAN network, having received the message correctly, performs an acceptance test to determine whether the data received are relevant for that station (”Select”). If the data are of significance for the station concerned they are processed (”Accept”), otherwise they are ignored.

A high degree of system and configuration flexibility is achieved as a result of the content-oriented addressing scheme. It is very easy to add stations to the existing CAN network without making any hardware or software modifications to the existing stations, provided that the new stations are purely receivers. Because the data transmission protocol does not require physical destination addresses for the individual components, it supports the concept of modular electronics and also permits multiple reception (broadcast, multicast) and the synchronization of distributed processes: measurements needed as information by several controllers can be transmitted via the network, in such a way that it is unnecessary for each controller to have its own sensor.