I follow that part.
I the past I have used RSLinx in a very basic way, to download programs to PLC, monitor data while on line, etc.
Working on a project where we will be gathering and storing data found within a CPU.
My minimal understanding of adding DDE/OPC topics, is that they are the "path" between the data storage file (maybe excel) and the CPU tag list (where the data is at within the CPU).
Does that sound about correct?