Can't agree Ron. The Device Net layer is the same for all but the way each PLC handles things is completely different. AB takes the Device Net data into a file where all the work is done for you in sorting out the data format etc. That is fine if you are hanging AB devices on the line. Have not tried other than AB on an AB PLC.
Omron, the other major proponent of Device Net, handle things quite differently in the PLC. Digital I/O is fine and very easy in both but explicit messaging is where it all happens. In an AB the file system sorts things out for you. Omron are far less brand oriented and when lots of information is read in by this method, you then have to swap bytes and then swap words to get things in the right order.
Had this experience with Omron CS1 PLCs with a mixture of Omron I/O blocks and AB Powermonitors 3000s. Digital I/O was very easy but the 3000s were read by explicit messaging, due to the amount of data in the things, and then the data had to be sorted in the Omron PLC.
Have just used Pepperl + Fuchs absolute rotary encoders on Omron CS1 PLCs. Speed was not a pre-requisite but accuracy was. Works great. Explicit messaging not required. Used the Omron configurator, allocated 2 words to each encoder and it was all over.
Quite impressed with the AB Powermonitor 3000s and the Pepperl + Fuchs encoders. Both work extremely well and both were priced well below their opposition. Both offer excellent bang for your buck.
Been there, done that.
Oh, by the way, did not go to any Device Net classes. Found it pretty easy and reliable to use and have used it on several projects. Found it much easier than Profibus, although it does not read and write as fast as Profibus.
beerchug
