CAN bus (Controller Area Network), an overview
CAN (Controller Area Network) is a serial bus system, which was originally developed for automotive applications in the early 1980's. The CAN protocol was internationally standardized in 1993 as ISO 11898-1 and comprises the data link layer of the seven layer ISO/OSI reference model. CAN, which is by now available from around 40 semiconductor manufacturers in hardware, provides two communication services: the sending of a message (data frame transmission) and the requesting of a message (remote transmission request, RTR). All other services such as error signaling, automatic re-transmission of erroneous frames are user-transparent, which means the CAN chip automatically performs these services.
The equivalent of the CAN protocol in human communication are e.g. the Latin characters. This means a CAN controller is comparable to a printer or a type writer. CAN users still have to define the language/grammar and the words/vocabulary to communicate.
CAN provides
- a multi-master hierarchy, which allows building intelligent and redundant systems. If one network node is defect the network is still able to operate.
- broadcast communication. A sender of information transmits to all devices on the bus. All receiving devices read the message and then decide if it is relevant to them. This guarantees data integrity as all devices in the system use the same information.
- sophisticated error detecting mechanisms and re-transmission of faulty messages. This also guarantees data integrity.
