ChristofferG

But it does only work with the Struct located in a Global Data Block with "Optimized block access" deactivated?

I think the documentation says the direct opposite?

Here is my case:
A UDT was created that fits the structure of the data transferd via Modbus.
If the UDT is used in a DB with "non optimized access" for MB_HOLD_REG everything works fine.
As soon as I use the same UDT in an DB with "optimized access" for MB_HOLD_REG I get the error status 16#8187 (The MB_HOLD_REG parameter has an invalid pointer. Data area is too small.).
If I use a DB with "optimized access" that only contains e.g. an array of Word for MB_HOLD_REG it also works fine.

My point is:
MB_SERVER is a optimized block, so:

• Using a structured non optimized DB makes it necessary to copy the whole paramater handed over by the variant IO.
• Using a optimized DB with an array only needs an reference at the variant IO but in the end I still need to do some extra work to fit it in my structure.

(For more details on that see: "2.6.5 Parameter transfer between blocks with optimized and non-optimized access" in Programming Guideline for S7-1200/1500)

Is there actaully no other way to solve this? Pick your poison?