CAN bus is compared with 485 bus
CAN(controller Area Network) is a kind of serial communication network which supports distributed control or real-time control effectively.
Compared with the RS-485 distributed control system based on R line.The distributed control system based on CAN bus has obvious advantages in the following aspects:
1)The CAN bus controller to work on the main way.All nodes in the network CAN access based on bus priority(depending on the message identifier) structure of non-destructive bitwise arbitration competition way to send data to the bus.and CAN agreement abolished the station address code,and replace it with the communication data, which CAN make the different mode receives the same data at the same time, these characteristics make up of the system. However,RS485 can only constitute the master-slave structure system, and the communication mode can only be carried out by the polling mode of the main station, so the real-time performance and reliability of the system are poor.
2)CAN bus is connected to physical bus through CANH and CANL,two output ends of CAN controller interface chip 82c250,and CANH end CAN only be in high level or floating state,CANLend CAN only be in low level or suspended state. In RS485 network, when there is an error in the system and multiple nodes send data to the bus at the same time,the bus will be short-circuited,thus damaging some nodes. In additon, CAN node CAN automatically close the output function in case of serious errors, so that the operation of other nodes on the bus will not beaffected, so as to ensure that there will be no problems in the network , and the bus will be in a "deadlock" state due to problems of some nodes.
3）CAN has perfect communication protocol,which CANbe realized by CAN controller chip and its interface chip meter, thus greatly reducing the development difficulty of the system and shortening the development cycle.These are incomparable by RS 485 which only has the electrical protocol for the instrument.
Compared with the RS-485 distributed control system based on R line.The distributed control system based on CAN bus has obvious advantages in the following aspects:
1)The CAN bus controller to work on the main way.All nodes in the network CAN access based on bus priority(depending on the message identifier) structure of non-destructive bitwise arbitration competition way to send data to the bus.and CAN agreement abolished the station address code,and replace it with the communication data, which CAN make the different mode receives the same data at the same time, these characteristics make up of the system. However,RS485 can only constitute the master-slave structure system, and the communication mode can only be carried out by the polling mode of the main station, so the real-time performance and reliability of the system are poor.
2)CAN bus is connected to physical bus through CANH and CANL,two output ends of CAN controller interface chip 82c250,and CANH end CAN only be in high level or floating state,CANLend CAN only be in low level or suspended state. In RS485 network, when there is an error in the system and multiple nodes send data to the bus at the same time,the bus will be short-circuited,thus damaging some nodes. In additon, CAN node CAN automatically close the output function in case of serious errors, so that the operation of other nodes on the bus will not beaffected, so as to ensure that there will be no problems in the network , and the bus will be in a "deadlock" state due to problems of some nodes.
3）CAN has perfect communication protocol,which CANbe realized by CAN controller chip and its interface chip meter, thus greatly reducing the development difficulty of the system and shortening the development cycle.These are incomparable by RS 485 which only has the electrical protocol for the instrument.
