485 communication of Siemens S7-200
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One of the Siemens S7-200 units in our factory has a 485 communication interface; it connects to Zhejiang University’s control system via pins 3 and 8 of port 0, and communication works properly. However, due to the large distance, we have added a human-machine interface on-site. The model chosen for this interface is Stepco 4532TE. When connecting it to the existing 485 line, communication is not possible, and attempting to connect it via pins 3 and 8 of port 1 on the PLC also results in no successful communication. Is it a problem with the PLC or has the human-machine interface not been set up properly?
PORT 0 can function as both a MODBUS RTU master and a slave. PORT 1 can only serve as the master station. This is the main difference between the two ports; as a result, the touch screen must be set as a slave. The ports 200 are 3 and 8. What about the wiring for the ports of your touch screen?
My touchscreen has 6 pins for power, and there’s another 5-pin connection for signals and ground
It should be a DCS that can be connected using signal wires; that’s how we connect them here
Firstly, pins 3 and 8 of port 1 on the PLC are connected to the human-machine interface. Since communication with the DCS is working properly, it indicates that the internal communication programs and variable addresses in the PLC are set up correctly; thus, there is no issue with the PLC itself. It is necessary to check whether the address of the touch screen is correct, as well as whether the configuration settings within the touch screen correspond to the variable communication addresses