CAN bus is a serial data communication protocol developed by German BOSCH from the early 80s to solve the problem of data exchange between numerous control and test instruments in modern automobiles. It is a multi-master bus, and the communication medium can be twisted pair, coaxial cable or optical fiber. The communication rate can be up to 1Mbps.

Completing the framing of communication data

The CAN bus communication interface integrates the physical layer and data link layer functions of the CAN protocol, and can complete the framing of communication data, including bit padding, data block coding, cyclic redundancy checking, and priority discrimination.

Theoretically unlimited number of nodes in the network

One of the most important features of the CAN protocol is the abolition of the traditional station address coding, and the replacement of the communication data block coding. The advantages of using this method allow the number of nodes in the network to be theoretically unlimited. The identifier of the data block can be composed of 11 or 29 binary digits, so that 2 or more different data blocks can be defined, and this encoding by data block also allows different nodes to receive the same data at the same time, which is very useful in a distributed control system. The data segment length of up to 8 bytes meets the general requirements for control commands, operating status and test data in usual industrial areas. At the same time, 8 bytes will not occupy the bus time too long, thus ensuring the real-time communication. CAN protocol adopts CRC check and can provide corresponding error processing function, which ensures the reliability of the data communication. CAN's excellent characteristics, high reliability and unique design are especially suitable for interconnecting the industrial process monitoring equipment, therefore, it is getting more and more attention by the industry and has been recognized as one of the most promising field buses. It has been recognized as one of the most promising fieldbuses.

Can realize free communication between nodes

CAN bus adopts multi-master competitive bus structure, with multi-master operation and decentralized arbitration of the serial bus and broadcasting communication characteristics. any node on the CAN bus can take the initiative to send information to the other nodes on the network at any time without regard to the primary and secondary, and therefore can realize free communication between nodes. CAN bus protocol has been certified by the International Organization for Standardization (ISO). CAN bus protocol has been certified by the International Organization for Standardization, the technology is more mature, the control chip has been commercialized, cost-effective, especially for distributed measurement and control system data communication between the CAN bus card can be arbitrarily inserted in the PC AT XT compatibility, convenient to form a distributed monitoring system.

Simple structure

Only two wires are connected to the outside, and the internal error detection and management module is integrated.

Transmission distance and rate

CAN bus features: (1) no master-slave data communication, any node can be initiated to any other (one or more) node data communication, relying on the nodes to determine the order of the communication of the priority of the information in order to determine the order of the communication of high-priority node information in the communication of the 134 μs; (2) more than one node initiated at the same time when the communication of a low-priority node to avoid the high-priority, the priority of the node to avoid the high priority, the node to avoid the high priority. (2) When multiple nodes initiate communication at the same time, the low priority will avoid the high priority, which will not cause congestion on the communication line; (3) The communication distance can be up to 10KM (the rate is lower than 5Kbps), and the rate can be up to 1Mbps (the communication distance is less than 40M); (4) The CAN bus transmission medium can be twisted pair cable, coaxial cable, CAN bus is suitable for short distance communication with large amount of data, or long distance communication with small amount of data, and the requirement of real-time is relatively high, and it is suitable for short distance communication with large amount of data or long distance with small amount of data. CAN bus is suitable for short distance communication with large data volume or long distance with small data volume, high real-time requirement, multi-master and multi-slave or each node is equal in the field.