Can I add "extensible parameters" to an existing normal function block?
I see your question has been unanswered since September. Perhaps you need to provide more information. Let me ask the following questions and if you can clarify, you may be able to get an answer ...
Based on the question, are you:
(1) Trying to use XML data types to supply data to an existin parameter on a Function Block, or ...
(2) Trying to add new parameters to an existing Function Block using XML, or ...
(3) Neither of these and it is something else ... please describe.
I assume you'd like to have extensible parameters to a function block in the AC 800M where you define the number of parameters of the input/output in question in the declaration pane of the POU editor.
If this is so, the answer is that this is not possible to do for an end-user.
A workaround might be to define several inputs and/or outputs. But the internal code will be more tricky to handle.