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Today we continue to introduce the technical explanation of S7-200smart Modbus-RTU Communication V20 Inverter.
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Since we are using the built-in RS-485 port of the S7-200smart CPU; at the same time, in the Modbus-RTU communication between S7-200smart and V20 inverter, S7-200smart acts as the master station, therefore we should choose the Modbus-RTU Master (V2.0) library. If using the signal board expanded RS-485 port, then use the Modbus-RTU Master2 (V2.0) library.
01
MBUS_CTRL is used by the master station for initialization, aiming to enable the Modbus protocol and configure parameters through the usage of related pin parameters.
02
Meaning of Pins: Detailed meanings of pins can be referred to in the system F1 help.
Mode: 1=Modbus protocol; 0=PPI protocol;
Band: Supported communication baud rates are 1200, 2400, 4800, 9600, 19200, commonly used is 9600.
Parity: Check methods include 0 no check; 1 odd check; 2 even check;
Port0: 0=CPU integrated RS 485 communication port; 1=optional CM01 signal board;
Timeout: The time the master station waits for the slave station’s response, in milliseconds, typical setting value is 1000 milliseconds (1 second), the allowable range is 1-32767; (commonly used is 1000).
Done: Initialization complete, this bit will automatically be set to 1;
Error: Communication error, specific error meanings refer to the Error parameter.
03
Actual filling situation takes S7-200smart reading the V20 inverter frequency as an example, see the image below
01
MBUS_MSG is used by the master station to send communication requests and process responses.
02
Meaning of Pins: Detailed meanings of pins can be referred to in the system F1 help.
En Enable: Only one read/write function (i.e. MBUS_MSG) can be activated at a time;
First Read/Write Request: Each time there is a new read/write request, this pin must be used and triggered with a pulse;
Slave Address: Selectable range 0-247, where 0 is the broadcast address, the actual range is 1-247;
RW Read/Write Request: 0 = read, 1 = write;
Addr Starting Modbus Address of the Slave: Choose the starting Modbus address of the slave to read/write based on actual requirements (e.g., 40001);
Count Number of Data: Allocated number of data to read or write during communication (number of bits or words);
DataPtr Data Pointer: Points to the starting address; if the master reads, the data read back will be placed in this data area; if the master writes, the data to be written will be placed in this data area;
Done Completion Bit: Read/write function completed, this bit will automatically be set to 1;
Error Error Code: Communication error, specific error meanings refer to the Error parameter;
03
Actual filling situation takes S7-200smart reading the V20 inverter frequency as an example, see the image below.
Alright, that’s all for today’s technical explanation. Practice more, learn more, and improve more.
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