What is the purpose of the deadband parameter in the DNP module?

The deadband parameter sets how event data is generated by your module as a DNP slave device. Take for instance the following configuration values:

AI Deadband : 1000 #0-32767 analog deadband value for events
AI Class : 3 #default class for analog input events

[DNP slave analog inputs]
# this area is to override the class (3) and deadband for the integer analog
# input database. The point # is the offset from the start of the analog
# input database.
#
# point#    class    deadband
start
    6    1    50
    7    1    10
    8    2    100
end

The AI Deadband being set to a value of 1000 will report all of the points (except those listed in the analog inputs override map) as being class 3 data (as set by the "AI Class" parameter being set to 3) and it will generate an event every time an analog input changes by a value of 1000 or more. This AI Deadband can be set to any value between 0 (don't generate events) to 32767 (generate an event when the value changes by 32767).

The "DNP slave analog inputs" section, allows the user to define classes and individual deadbands for each point. For instance with the above configuration if AI point 6 changes by a value of 50 or greater, then a class 1 event will be generated for that point. If AI point 7 changes by a value of 10 or greater than a class 1 event will be generated for that point. And finally if AI point 8 changes by a value of 100 or greater, then a class 2 event will be generated for that point. These parameters allow you to configure either all of the AI points with one deadband and class assignment by setting the "AI Deadband" and "AI class", or define each point individually in the [DNP slave analog inputs] section.

By utilizing both sections you can define a default for all points, then define specific points with various deadbands and class assignments.