Are you able to control the display via RS232 when the display is five cable feet from the PLC? If you can, you have an RS422 problem. If you can't you have an RS232 problem.
Divide your universe to locate the problem.
A good answer is easier with a clear question giving the make and model of everything. "The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
