Why can’t the PLC’s Ethernet port communicate in a protocol-free manner like the serial port?
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Is it impossible from a technical standpoint, or do the manufacturers not want their products to be able to use Ethernet for communication?
All communications are based on protocols, and serial ports are no exception.
Without a protocol, it’s not called a communication cable – it’s called an electrical cable; P
It is the free-port protocol, or a protocol similar to MODBUS RTU; in serial communication, commands for sending and receiving data are handled directly, allowing PLCs of different brands to communicate with each other directly. But Ethernet ports cannot do that
Learn about Modbus TCP