Look up DFB (Derived Function Block) in the help file. You can create the logic and then turn it in to a DFB using the Unity Software. In addition to the DFB you can also create a EFB (Elementary Function Block) but this will require the purchase of the EFB toolkit.
For functions, I recommend to use the DFB capabilities. If you are a "C" expert or if you are searching for an optimized scantime, then the use of the EFB Toolkit will match your need. In both case, the fuinctions developped can be integrated to your library or the one you have shared wxith other developers. The version of the function will be managed by the system so that each time you change the type you can decide or not to update all your other projects.
Regarding Data, the best way is to work without mapping to the memory. This can be done for elementary type or for your customized object with the DDT.
You can even go further by programming all your lines without thinking about the hardware. that's the IODDT. You just align the IODDT to a hardware module at the very end.
All these capabilities should help you to better reuse things.
