Control Area Networks

CAN Benefits

CAN is low cost:

• Fast serial bus with two wires: good price/performance ratio

• Low cost protocol devices (controllers,transceivers) available mainly driven by high volume production in the automotive market.

CAN is reliable:

• Sophisticated error detection and error handling mechanisms results in high reliability transmission ex: 500 kbits/s,25% bus load, 2000 hours per year. One undetected error every 1000 years.
• Erroneous messages are detected and repeated.
• System-wide data consistency (every bus node is informed about an error)
• Faulty nodes automatically withdraw from bus communication
• High immunity to Electromagnetic Interference.

CAN is real-time:

• maximum data rate is 1 MBit/s @ 40m bus length (still about 40 kbit/s @ 1000m bus length)

• Short message length (0 to 8 data bytes / message)(Larger data can be split up into several messages).

• Low latency between transmission request and actual start of transmission.

• Bus access handled via CSMA/CD w/ AMP method (message with the highest priority wins arbitration without losing any time).

CAN is Flexible:

• CAN allows Multi-Master Operation(every CAN node is able to access the bus individually).

• CAN Nodes can easily be connected / disconnected (i.e. plug & play).
• Number of nodes not limited by the protocol.

CAN means Multicast / Broadcast Capability:

• CAN is not node-oriented but message-oriented.
• Message identifier specifies contents & priority of the message.
• Messages can be easily sent to multiple / all nodes simultaneously.
• All nodes simultaneously receive and work on common data.

CAN is standardized:

• ISO-11898 (high speed applications).
• ISO-11519-2 (low speed applications).

How it all began...