The slots in the standard frames are predefined slots for the different elements a synchronous machine controller may have, i.e. the element Power System Stabilizer (ElmPss), etc. The names of the input/output variables of each slot have to fit to the DSL element which will be inserted into the slot. This means, if you create an own ElmPss or ElmVco, the names of input and output variables in your new block diagram have to match the inputs/outputs of the slot, whereby not all
variables of the slot have to be used in the inserted block diagram or vice versa.