I am working on a appliance control that will communicate via Modbus. Looking on some guidance on reserved sub-function codes for function 43 Encapsulated Interface Transport. The spec defines sub-functions 13 and 14 as public.

Annex A says:

The following function codes and MEI Types shall not be part of this published Specification and these function codes and MEI Types are specifically reserved: 43/0-12 and 43/15-255. In this Specification, a User Defined Function code having the same or similar result as the Encapsulated Interface Transport is not supported.

I see in specifications for some Schneider Electric devices the use of some reserved sub-function codes for function 43.

Function 43–15: Read Date and Time
Function 43-16: Write Date and Time

Am I free to implement this behavior in my control?

In addition I see they have a private function:

Function 100–4: Read n Non-Adjacent Words

Can I implement this behavior?

 

Maybe I should clarify. My appliance will be a Modbus server controlled by a building management system.