AI810 AI835 ABB I/O module 3BSE008520R1 new 8-channel

Description

Under the MODBUS communication protocol, the frame structure of AI810 is different for different command function codes. For the read register command, the frame structure of the main station of MODBUS is: 2-byte address code, 1-byte function code, 2-byte data address code, 2-byte CRC check code; The MODBUS slave response frame structure is: 2 byte function code, 1 byte total number of response area bytes, N byte response data, and 2 byte CRC check code.

Although the physical layer protocol is different from the data link layer protocol, the implementation of the AI810 data link layer protocol must be based on the fact that the physical layer connection between the two communication parties has met the requirements, and that the information interaction can be realized barrier free.
This rule must be completely and thoroughly implemented in the seven layer protocol of the ISO/OSI model. In the ISO/OSI model, the low-level protocols of the communication parties must establish a transparent and fault free connection and information exchange relationship for the upper protocol. In other words, the hierarchical relationship must be absolute.
From the data link layer AI810 to the network layer. Its task is to form a field bus information exchange network.
The functions of the network layer include: packaging the communication frames into data packets, and then sending the data packets to the other party.
Because the network structures of the two communication parties may be different, the same network needs to be connected with a bridge, while the heterogeneous network needs to be connected with a gateway.
There may be multiple channels between networks. There are multiple paths for sending data packets. The element responsible for selecting the path is called a router. Router not only determines the real data exchange network path, but also can build a virtual network path, and also determines the sending order of data packets. Therefore, routers are the most complex and critical equipment in the network layer.
In the OSI model, the combination of physical layer, data link layer and network layer is called fieldbus, and its communication interface is an 8-pin RJ45 crystal head. It is obvious that RJ45 is totally different from RS232/RS485/RA422.
Data packets in the network layer are combinations of data frames. Generally speaking, data grouping is a short article or a page of data combination unit to be transferred.

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