Quote Originally Posted by wysota View Post
How exactly do you "observe" the data passing through the port? If you use another application for that, it could be that it steals the data, as it was already suggested.
i make sure i have write the data succeedly. the PLC can run with my program that i write to it. According to the protocol of the MELSEC-FX PLC, the PLC will answer me some information.
i can't get any data even if i close the serial port monitor as i have state it after i try as the suggestion.