In most cases, you should use the FormAttributeToValue method, instead of the FormDataToValue.
The recommendation is due to considerations of unification of the application code and the fact that the syntax of the FormAttributeToValue is simpler than FormDataToValue.
Procedure Test()
Form=Doc.GetForm("DocumentForm");
FD = Form.FormDataToValue(Object, Type("ValueTable"));
EndProcedure
Source: Using of FormAttributeToValue and FormDataToValue methods (RU)