Objects declared in a system or device that implements DNP protocol in Slave mode can be grouped into classes. DNP protocol defines the following classes:

•Class 0: It means all objects, that is, when starting this Driver, on the Master side, can perform a class 0 (zero) request, and as a response the Slave side sends the current value of all declared objects

•Classes 1 to 3: These are entities that temporarily store lists of events or changes in objects. Each object must be configured on the Slave side to generate events when changes occur, and usually there is a pattern among DPN users to reserve class 1 for digital events, class 2 for analog events, and class 3 for counters