EDDI is a sequencer based programming structure that uses sets of ladder logic rungs, called cells, for every action required in the program. For example, there is a set of about 12 rungs to control a motor. This is due to the way the PLC program interacts with the HMI (the dynamically indicated part). Not only do you get alarm messages, but dynamically updated information as to what the machine is doing next. I've only seen it at one plant, and it has been customized to meet their requirements. If it's implemented properly, it makes running and troubleshooting the machine a breeze. Unfortunately, many OEMs skip some of the initial program design steps causing headaches down the road.
If you have any specific questions, I can try to answer them for you.
