The broad range of application areas for IEC 61131-3 not all implementations use exactly the same data types. The certification according to Conformity Level (CL) implies that the PSE supplier selects the data types supported by his product matching his compliance statement. All supported IEC features are tested. This means that the test is a YES or No test, there can be differences between two certified products. These differences can influence the reusability of function blocks of user derived
The data types total number as specified in the Standard amounts to 26. These range from simple digital Yes/No to potential complex structures. Therefore, CL has 26 options, data type supported or not supported. Only the supported data types are used for testing.
Additionally Reusability Level (RL), is dedicated to making the programming units functions and function blocks reusable on a different PSE. This is done via exchange in a plain textual format of the language Structured Text (ST). A conversion tool to or from ST can be included for representation in other languages. This is a major, but natural contribution of PLCopen to the IEC 61131-3 standard.
Historically there exists a lower class which called Base Level, defining core kernel per language of the standard. It is feasible to develop applications based on it although rather restricted. Base level provides an entrance level for the suppliers, showing their commitment to the standard. It provides a normalized interpretation of the standard for the users, especially important if they have to work with systems of different vendors.
TC4 – Communications work on the relation between programming languages and communication, like the mapping of CANopen and Profibus.
TC5 – A safe software prepares recommendations for applying the standard of IEC 61131-3 to and adapting it for safety related applications, specially focused on new safety standard IEC 61411 and 61408.
TC6 – XML works on the specification schemes of XML for all languages as well as full projects.