ProSoft Technology MVI69-DNPSNET - Manual (Page 92)

MVI69-DNPSNET ♦ CompactLogix or MicroLogix Platform Reference
Distributed Network Protocol Interface Module
Page 92 of 119 ProSoft Technology, Inc.
November 3, 2008
5.3.5 Module Operation
After the system has been designed and the system is set up, the module will be
ready to operate. When the module is first initialized, it will read the configuration
file (DNPSNET.CFG on the module's Compact Flash Disk). After the file is
processed, the module will use the data to set up the data structures of the
application. If any errors are encountered during the initialization process, the
default value for the parameter will be assigned and used.
The module will next check if the output initialization feature is utilized. The
option permits the PLC to set these read-only data at startup. There is no static
memory available on the module to remember the last values for these data
types. In order to prevent a "shock" to the system at boot time, this option can be
used to set the module's database to the last transferred set of data. If this option
is enabled, the module will request the binary and analog output from the PLC.
This is done using blocks 1000 to 1149. Ladder logic must transfer the data for
this feature to operate.
After the successful initialization of the module, the program will start the normal
data transfer between the module and the CompactLogix or MicroLogix
processor. The program will send a read block first and then wait for a write block
to receive data from the PLC. This alternating sequence of read and write will
continue as long as the program is running. The program will update the DNP
memory areas in the module with the new data and generate events for digital
and analog input status changes.
If the module is configured for unsolicited messaging, the module will
immediately send an unsolicited response once the remote master connects to
the module, informing the master of a module restart. The module will not log
events or process any data read operations from the master until the master
clears the restart IIN data bit. The master must also synchronize the time with the
module before events will be generated if the module is so configured. The
master is also responsible for enabling the unsolicited message facility in the
module by sending the Enable Unsolicited Messaging command to the module.
If the module is not configured for unsolicited messaging, the DNP master must
clear the restart IIN bit before the module will start logging events. The master
must also synchronize the time with the module before events will be generated if
the module is so configured.
Additionally, the program will listen on Port 1 for requests. This is the debug port
for the module and transfers module information to an attached terminal. Refer to
the Diagnostics and Troubleshooting section for a complete discussion on the
use of this important feature.