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Semantic Error (SEM1099): The method '...' has no return value.

A method of a function block does not define a return value.

On creation of a new method, you have to select a return data type in the 'Signature' editor of the method. BOOL is set as default value.
The 'Return type' drop-down list allows to select an empty entry thus specifying a method which does not return any value.

Remedy