Practical_modern_SCADA_protocols_-_dnp3,_60870-5_and_Related_Systems

380 Practical Modern SCADA Protocols: DNP3, 60870.5 and Related Systems
The DNP3 protocol also caters for expansion & evolution of the standard without
detracting from the strengths of inter-operability that it promotes. This is achieved by an
object-oriented approach to the data. Data objects can be added to the DNP3 standard
without affecting the way that devices inter-operate.
The PDS RTU supports DNP3 to sub-set level 2 implementation with a range of
additional features from the DNP3 standard.
In summary the PDS RTU provides the following facilities for use of DNP3:
• SCADA data configuration
• DNP3 operation on multiple ports
• Networking DNP3 frames
• Peer-to-peer communication
• Individual point range queries
15.1.6 Data mapping in RTUs
This section describes the data mapping, or indexing used by the RTUs.
PDS software architecture
The PDS processor has many tasks running concurrently. Various RTU facilities are
accessible, external to the PDS RTU, in three ways:
• Direct mapping of physical input and output points
• Mapping of processed or derived data for SCADA master or peer-to-peer
for other RTUs
• Configuration and status information
PDS RTU data is arranged into two basic types, binary and analog data. Each element
of these two types is identified with a point index that ranges from 0 to 65 535. A single
binary point is one bit of information and may be accessed using DNP3 binary input and
binary output objects. Analog points are generally 16-bit, but 32-bit points are included
that can be used to represent either 32-bit integers or 32-bit floating point quantities via
DNP3 objects. DNP3 counter objects are also supported.