allen bradley rslogix
Hello CrabMan,
OnLine programming means that you are able to modify the PLC program with the PLC running the application.
Bottom line of Allen Bradley PLCs (MicroLogix) can only be programmed Off Line, however, from the SLC500 and up you don't need to stop the PLC to do manteniance or modification of the program.
That capabilty is important if you cuold not afford to stop all the controlled process to do minimal modifications. (think in a chemical process plant, by example).
Obviously, you must be carefull with your modifications, as you can blow anything in case of programming mistake.
Hope this helps you to select your package.
Regards