Modbus communication address setting - solution - Huaqiang Electronic Network

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Data exchange between devices can be realized by using the Modbus protocol. Modbus communication theoretically supports four Modiconplc addresses, namely 0*, 1*, 3* and 4*, which represent data addresses such as open (middle coil), open, analog, and analog (intermediate register). It does not correspond to the opening, opening, molding, and molding addresses in Siemens or other devices. Can be understood as 0* and 1* corresponding bit address read and write operations, 3 * and 4 * word address read and write operations.
Here, 0*, 1*, 3*, and 4* indicate that the length is 5 digits, and some are 6 digits. Actually, it has nothing to do with Modbus communication, but it is related to the representation of the software.
The most common use of Modbus communication is the RTU read request format:
Slave address (1 byte), function code (1 byte), slave data start address (2 bytes), read data length (2 bytes), CRC check (2 bytes) )
It can be seen that it is only necessary to set the starting address and communication length of the starting slave data area.
In particular, the Modbus address complies with the IEC1 address standard (minimum address is *1), and Siemens complies with the IEC0 standard (minimum address is 0, such as M0.0). Therefore, different standard addresses need to do address translation when doing communication, that is, add 1 operation.