What is the disadvantage of profibus comparing to Ethernet?

The vast majority of PLC communications is done via RSC and twisted pair cables. Most PLCs have an RS port and are capable of handling communications with host computers, printers, terminals, and other devices. Maximum transmission speed is.2 Kbps.

The distance and data transmission rates are standards for the various interfaces. Their actual performance is a function of the driving devices and varies significantly between manufacturers. As such, you should consult the manufacturer's specifications for actual distance and data transmission rate capabilities.