{"id":1621,"date":"2012-04-04T02:18:31","date_gmt":"2012-04-03T22:48:31","guid":{"rendered":"http:\/\/fxplans.com\/web\/?page_id=1621"},"modified":"2012-08-31T10:14:16","modified_gmt":"2012-08-31T06:44:16","slug":"controller-are-network","status":"publish","type":"page","link":"http:\/\/fxplans.com\/web\/controller-are-network\/","title":{"rendered":"Controller Are Network"},"content":{"rendered":"

Introduction<\/span><\/p>\n

This report describes some of the di\u000berent network protocols used in the automotive\u00a0industry and then discusses similarities and di\u000berences between them.\u00a0The report is divided into three main sections. The \frst describes the Controller Area\u00a0Network (CAN), developed by Robert Bosch. This was identi\fed as the most important\u00a0network system for the project. There are several other protocols being developed for\u00a0use in the industry, however, especially for \\drive by wire” applications as well as earlier
\nprotocols which might still be encountered. Some of these other protocols are described in\u00a0the second section. The third section then considers similarities and di\u000berences between\u00a0these protocols from the point of view of the project, so discusses issues of interest for
\nmodelling and simulating the networks.\u00a0The references consulted are listed in a bibliography. Much of the investigation for this
\nreport was done using the Web, so many of the sources are actually web-site urls rather\u00a0than published papers. In the nature of the Web it is likely that some of these sources\u00a0will become unavailable, but they have been checked during preparation of this report.
\nMany of the web sources have been downloaded and saved or printed, so if a reader of this\u00a0report cannot \fnd a desired source, it might be worth getting in touch with the author.<\/p>\n

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Controller area Network<\/span><\/p>\n

This section describes some of the features of the Controller Area Network of interest in\u00a0modelling networks using the protocol and also brie y discusses these features from that\u00a0point of view. It is therefore not a full description, the sources referred to should be
\nconsulted for further information.\u00a0Controller Area Network (CAN) is a network protocol developed by Robert Bosch
\nGmbH for vehicle systems, but which is coming into use for linking distributed controllers,\u00a0sensors etc in other \felds. Bosch have published a speci\fcation. The protocol has\u00a0been adopted as a standard by the ISO, reference ISO11898. Any reference herein to the\u00a0spec” means the Bosch speci\fcation, not the ISO one, which I have not seen (it costs!).\u00a0CAN is a CSMA\/CD protocol (some sources have CSMA\/CR for similar protocols)\u00a0that uses non-return to zero coding with bit stu\u000eng. It supports speeds of up to 1Mb\/s\u00a0so is an SAE class C protocol, suitable for real time control applications. There is a brief\u00a0explanation of the classes of protocols in section.
\nMessages are not addressed to intended recipients, but the sender’s identi\fer is included, and this tells the receivers what data it contains so the receiver ignores it if it is\u00a0not interested. Messages’ identi\fers give the priority of the message, so the priority of
\nmessages is decided at the design stage.
\nIn \u00a0there are two standards for CAN 2.0, imaginatively called A and B. These\u00a0di\u000ber in message format (see section 2.2), B has an extended message format, with a 29\u00a0bit identi\fer, as opposed to A’s 11 bit one.\u00a0In basic can (not to be confused with CAN \\A”) each controller on the network is\u00a0interrupted by every message on the bus. In full CAN, the CAN devices add \fltration of
\nthe messages, and will only pass messages with speci\fed identi\fers on to its associated\u00a0controller, so a controller is only interrupted by those messages the CAN terminal passes,\u00a0that is those of interest to that controller.\u00a0The notes on CANbus in Automobile Electrical and Electronic Systems draw attention to the di\u000berence between having a local intelligent control module (for example,for all functions located in the driver’s door) and having the intelligence actually in the\u00a0actuators, so control is distributed, and each actuator (and each sensor) is on the bus\u00a0itself.<\/p>\n