how to make a user defined enum as an input for a ladder function

[curtharrington1]

I am controlling a VFD via modbus where there is a forward bit and a reverse bit in a command word.  I need to implement logic to set/reset the bits based on the direction the VFD needs to move and I want this logic to be wrapped up in a single user defined function block using an enum as the input to protect against invalid arguments being passed.  I'm not sure if there is a way to do this but I've tried using the clunky LIST feature which did not work.  I know some of the UniLogic supplied blocks do this.  Does anyone have any thoughts on how to do this?  
 

 

[Saragani]

Currently, you have no way of defining an enum, or defining that a function-in is of type enum.

 

[Rivka]

Please note that although you cannot force the user to use the function correctly, you can guide him to do so, using comments on parameter In and Out, and run-time checking, as follows: