The CAN Protocol The CAN messages The CAN bus is a broadcast type of bus. This means that all nodes can "hear" all transmissions. There is no way to send a message to just a specific node; all nodes will invariably pick up all traffic. The CAN hardware, however, provides local filtering so that each node may react only on the interesting messages. CAN uses short messages - the maximum utility load is 94 bits. There is no explicit address in the messages; instead, the messages can be said to be contents-addressed, that is, their contents implicitly determines their address. Message Types There are four different message types (or "frames") on a CAN bus: the Data Frame, the Remote Frame, the Error Frame, and the Overload Frame. The Data Frame The Data Frame is the mon message type. prises the following major parts (a few details are omitted for the sake of brevity): the Arbitration Field, which determines the priority of the message when two or more nodes are contending for the bus. The Arbitration Field contains: For CAN , an 11-bit Identifier and one bit, the RTR bit, which is dominant for data frames. For CAN , a 29-bit Identifier (which also contains two recessive bits: SRR and IDE) and the RTR bit. the Data Field, which contains zero to eight bytes of data. the CRC Field, which contains a 15-bit checksum calculated on most parts of the messa
