ProSoft Technology MVI71-DNP - Manual (Page 99)

Reference MVI71-DNP ♦ PLC Platform
DNP 3.0 Master/Slave Communication Module
ProSoft Technology, Inc. Page 99 of 172
August 23, 2007
The following illustration shows the interaction of the binary and analog output
points with the databases.
The DNP database consists of data from the DNP master on the slave port. This
data is passed to the PLC and to the IED units through the command list. The
IED database contains control data generated in the PLC. This is the only data
path for PLC control of IED units on the DNP master port. A command must be
set up to handle the transfer of data from the IED database to the IED unit. The
last value databases are used for exception processing of control commands.
Commands can be configured to only generate a message if there is a change in
the database. The current values are compared against the last value database
to recognize the changes. When a change is recognized, the DNP master port
executes a command to the specific IED unit containing the new data.
Side Connect Interface
Data is directly transferred between the module and the PLC data files over the
side-connect interface. Code within the module automatically handles the
transfer of the data using the module's configuration. Up to 1000 words of data
can be transferred on each read or write operation. Because the interface
permits direct memory access, each data transaction is almost instantaneous.
This interface requires none of the ladder logic or BTR/BTW operations required
by the block transfer mode. Each data type used by the module must have a
corresponding PLC data file in order for the data transfer to occur.