[PinguTS]

Thanks for referencing. I still have one of the original specification somewhere in my closet, when I was asked to review it.

They are made to look alike valid Ethernet frames. The idea was: how to make Interbus look alike Ethernet and how to make some patents to make money out of it. Originally you had to buy the controllers from Beckhoff. Now they are integrated by many µC, but still they have to pay licensing fees to Beckhoff.