What protocol should be used to send and receive data from Siemens 200PLC free port?

First of all, we must determine the agreement between the instrument and PLC.

Look at the instruction manual of the instrument. Is its data format free port mode or Modbus or something else?

Secondly, if it is a free port mode, you can use the serial debugging assistant to realize the communication between the computer and the instrument. The measured value of the instrument can be obtained on the computer.

Finally, PLC programming and TD display are designed.

1. The data format sent by the instrument depends on the instrument manual.

2. You send 16#4 1 to PLC by computer, and debug the program by serial port.

3. The serial debugging assistant can be used to monitor and analyze the signals on the serial line. The program is installed on a personal computer.

Between PLC and instrument: free port communication mode, which can be monitored by PC using serial debugging program.

Between PC and instrument: free port communication mode, which can communicate through serial port debugging program.

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