Defining Class 1/2/3 Items
Class 1/2/3 items are defined by the modifiers :c1, :c2, and :c2. They read their objects with a class 1/2/3 poll, which returns values for all objects in class 1/2/3 whose values have changed since the last class 1/2/3 poll. The object must be in the class specified by the modifier, and collection of that class must be enabled at the device. Otherwise, responses to the class 1/2/3 polls will never contain a value for that item.
ACM has no way of determining which objects are in class 1/2/3 for any given device. It can’t prevent an item from being defined with the wrong class. It will allow items for the same object to be defined with multiple class 1/2/3 identifiers, even though the item can only be in one of the classes in the device. The user is responsible for determining and defining the correct class for the object.
Initializing Class 1/2/3 Items
Class 1/2/3 items will be initialized with class 0 poll (all objects in class 1/2/3 are also in class 0), unless the option to disable class 0 initialization is selected.