UDT optimization with none access attribute

Starting with ControlLogix firmware version 18.x, using the Rockwell RSLogix 5000 Programming Software, UDT tags, and their elements can be configured with an External Access property setting of Read/Write, ReadOnly or None. The None setting is specifically meant to define a private tag within the processor, which is not exposed to components outside of the controller, such as the ABCIP Communication Driver. This affects the UDT optimization capability in the ABCIP Communication Driver. This also affects Add On Instructions behavior, which makes extensive use of UDTs. For these reasons, UDTs with elements having the External Access property set to None is not supported. UDTs must not contain any elements with External Access property set to None when the UDT optimization option is checked in the ABCIP Communication Driver.

Important: You must reset, or deactivate and reactivate, the Communication Driver if you change the access rights of an element in a UDT from None to ReadOnly or Read/Write.