How to use UDT as inout in a FB

Hi All,
I am new to this forum so don't flame on me if i forgot to do sth or did not do it precisely

I have the same problem as was already mentioned before in a thread:
http://www.plctalk.net/qanda/showthread.php?t=43994

I´ve made a FB which I am to use as a multi instance.
I want to pass data in/out of this FB and therefore I made a UDT with the structure of the data.

In the FB I declare a new inout with datatype of the above UDT, I´m using an inout since there are data which I should both read and write to in this struct.
I made the code in the FB, so far so good ..

Next step I called the FB above from another FB, but when trying to declare data at the actual inoutI all time get a fault that says the data on the actual side are not matching the data in the FB I call.

Click to expand...

The problem is basically with passing the UDT IN_OUT structure from the Higher FB to the lower FB. I don't understand the solution in the thread mentioned above as its is 4 years old, picture missing and the project opens corrupted on my PC.

Does anyone know how to solve this problem? I would be really grateful.

I am using Simatic S7 V5.5 + SP2 and CPU 315-2 DP.

You cannot pass a IN_OUT UDT parameter from a calling FB as an IN_OUT UDT parameter to a called FB. You will need to revise your program structure.

I have already done it by separating the data into IN and OUT UDTs.
But can you tell me exactlly why it is not possible to pass IN_OUT UDT parameter from a calling FB as an IN_OUT UDT parameter to a called FB?
A pointer error? I just don't get it why it is possible to do it with IN or OUT UDTs and not IN_OUT?

IN and OUT parameters of type UDT are passed by value (i.e. the data is copied to/from the instance DB), for IN_OUT parameters of type UDT they are passed by reference (pointer) and hence cannot be passed on.

This is strange for me, bacause i have an expereience with C++ and pointer to a pointer is not a problem there. Thought Siemens know how to handle this kind of stuff. Great thanks for the explanation though.

Case solved.