CAN belongs to the bus-type serial communication network. Due to its adoption of many new technologies and unique designs, compared with general communication buses, CAN bus data communication has advantages such as high reliability, strong real-time performance, and flexibility. Specifically, these are summarized as follows:
(1) CAN operates in a multi-master mode, where any node on the network can actively send information to other nodes at any time without distinguishing between master and slave. The communication method is flexible and does not require node addresses or other node information. Using this feature, it is convenient to form a multi-machine backup system.
(2) The node information in CAN is divided into different priorities, which can meet different real-time requirements. High-priority data can be transmitted within 134μs at most.
(3) CAN adopts non-destructive bus arbitration technology. When multiple nodes send information to the bus simultaneously, nodes with lower priority will actively exit sending, while the highest priority node can continue to transmit data without being affected, thus greatly saving the arbitration time for bus conflicts. Especially under heavy network load, network paralysis will not occur.
(4) CAN can realize point-to-point, one-to-many, and global broadcast transmission and reception of data through message filtering without special "scheduling."
(5) A node on CAN can actively request other nodes to send information. This characteristic is called "Remote Transmission Request" (RTR).
For example, the central safety system in a car frequently updates critical sensor information such as airbags. However, some information, like oil pressure sensors or battery voltage sensors, may not need to be received often. To ensure that these devices are working properly, the system must periodically request relevant information from such devices to check the entire system's operation. Designers can use this "remote transmission request" feature to reduce network data traffic while maintaining the integrity of the entire system.
(6) The straight-line communication distance of CAN can reach up to 10km (at a rate below 5Kbps), and the maximum communication rate can reach 1Mbps (with the longest communication distance being 40m at this rate).
(7) The number of nodes on CAN mainly depends on the bus drive circuit, currently reaching up to 110; message identifiers can reach up to 2032 (CAN2.0A), while the extended standard (CAN2.0B) almost has no limit on message identifiers.
(8) Short frame structure is adopted, with short transmission time, low probability of interference, and good error detection effect.
(9) Each frame of information in CAN has CRC check and other error detection measures, ensuring extremely low data error rates.
(10) The communication medium of CAN can be twisted pair, coaxial cable, or optical fiber, offering flexible choices.
(11) CAN nodes have the function of automatically shutting down output in case of serious errors, so as not to affect the operation of other nodes on the bus.