ABB Relion 615 Series Protocol Manual page 14

Section 2
DNP3 overview
8
Data link responsibilities:
• Exchange of SDUs between peer DNP3 data links
• Error notification to data link user
• Sequencing of SDUs
• SDU delivery quality.
Link-layer confirm usage is deprecated.
See the DNP technical bulletin TB1998-0402, section 3 for details
at www.dnp.org.
Transport pseudo-layer
To support advanced RTU functions and messages exceeding the maximum data
link frame length, a transport pseudo-layer which implements message assembly
and disassembly services was adopted. This pseudo-layer is actually a super-data
link transport protocol, which is normally included in some OSI protocol data links.
Transport functions:
• Fragmenting user data into one or more data link frames and transmitting the
data to the data link layer
• Assembling the data link frames received from the data link layer into user data
• Controlling all aspects of the data link excluding data link configuration
Transport responsibilities:
• Exchange of SDUs between peer DNP3 transport pseudo layers
• Error notification to transport users
• Sequencing of SDUs
Application layer
The application layer is responsible for performing operations on data objects
defined by the device or on the device itself. These operations can be: returning
actual values (read function), assigning new values (write function) if the object
represents control points, arming and energizing the output point (select, operate or
direct operate functions) and if counters are used, storing actual values (freeze
functions) and clearing the counters.
Many objects may be assigned to event classes. The DNP3 protocol defines four
classes; 0 for static data and 1, 2 and 3 for event data.
Binary inputs and analog inputs may be assigned to class 0. Binary events and
analog events may be assigned to classes 1, 2, or 3. If a binary event or analog
event is in class 1, 2, or 3, the corresponding input should be in class 0. The
configuration GUI provides this behavior. Any point which is not in class 0 will
not be returned in a class 0 scan, however, its static value may be read explicitly.
1MRS756709 D
615 series
Communication Protocol Manual