Rockwell Automation 1758-RTU202 DataSite Software User Manual FRN 1.2 - Manual (Page 236)

Publication 1758-UM002D-EN-P - October 2010
236 DataSite DNP3 Configuration Utility (DS DNP3)
DNP3 Class Objects
Under normal circumstances, each data type can be divided into static objects
and event objects. A static object contains the current value of objects, and an
event object is brought about by the results of data changes.
In DNP3, there are four kinds of class objects:
• Class 0
• Class 1
• Class 2
• Class 3
A Class 0 object contains all of the static data. Class 1, 2, and 3 objects are
event objects. This classification provides a method to define data priority.
Class 1 is the highest priority, and class 3 is the lowest.
The allocation of class objects can increase the efficiency of communication
between the master station and the slave station. For example, the master
station can scan high-priority data more frequently, and the slave station only
returns the changes in event data. The master station can obtain all the static
data without priority allocation from the slave station through the scan of class
0 data.
DNP3 allows the slave station to send the change information of the event
object proactively to several master stations (send unrequested response
information or exception report). The information is transmitted according to
class objects, such as the data which can be set to transmit the data of the
highest priority class 1 only.
DNP3 Internal Indication (IIN) Sign
The Internal indication (IIN) sign object is an important data object in DNP3.
The IIN sign is set by the slave station to indicate its internal state and
diagnostic results such as the appearance of class event, equipment error,
equipment startup and equipment reset.