ProSoft Technology MVI46-DNP - Manual (Page 60)

MVI46-DNP ♦ SLC Platform Reference
Master/Slave Communication Module
Page 60 of 143 ProSoft Technology, Inc.
August 23, 2007
5.2.3 Module DNP Protocol Operation
Unsolicited Messaging
If the module is configured for unsolicited messaging, the module immediately
sends an unsolicited response out Port 1 (Primary DNP port) 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 are
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.
Solicited Messaging
If the module is not configured for unsolicited messaging, the program listens on
Port 1 for DNP messages from a DNP master and sends responses to requests
after initialization. The DNP master must clear the restart IIN bit before the
module starts logging events. The master must also synchronize the time with
the module before events are generated if the module is so configured.
If the DNP master port is used, the port starts processing the command list. It
sends commands and requests out the port to slave units. Data acquired is
placed in the correct database in the module. Event messages received from the
IED units are placed directly in the event buffer or the values are placed in the
database. The communication statistics for each slave unit is tracked by the
module and is available for the SLC to request.
While the program is running, a status/error table is maintained. This data is
automatically passed to the SLC at a frequency set in the configuration. Refer to
the following section on the contents of the table.
If an error is encountered in the module's program, it is logged to the error list
maintained by the system. The program maintains a list of the last 60 errors. This
data is automatically passed to the SLC at a frequency set in the configuration.
Refer to the following section on the error codes contained in the list.
If the module is configured to use the secondary slave DNP port (Port 2), the
module may automatically switch communications to that port under the following
conditions:
ƒ
If the module receives a request on the port from the master
ƒ If unsolicited messages are enabled and the module is configured to switch to
the port if application confirm messages are not received while using the
primary port (user sets the number of reties in the configuration)
Communications will switch back to the primary DNP port when the module
receives a message on that port. If the module restarts, communications will
always be attempted on the primary DNP port first.