When working with an XLR PRO and an Allen Bradley 9210 PLC, you need to configure the PLC's remote.opt file so that the DTR line is always high. That can be done by using the Command /DTR+. What this does is sets the /DTR line at an active high state which in turns tells the XLR that you are using an RS232 connection. All other settings within the radio or PLC can be used in their default or point-to-point configuration.
Aug 23, 2017