ProSoft Technology MVI94-DNP - Manual (Page 93)

MVI94-DNP ♦ Flex I/O Reference
DNP 3.0 Server over Ethernet Communication Module User Manual
ProSoft Technology, Inc. Page 93 of 131
December 17, 2010
5.4.4 Master Driver
In the Master mode, the MVI94-DNP module is responsible for issuing read or
write commands to slave devices on the DNP network. These commands are
user-configured in the module via the Master Command List read from the
module’s Flash. Command status is returned to the processor for each individual
command in the command list status block. The location of this status block in
the module’s internal database is user-defined. The following flow chart and
associated table describe the flow of data into and out of the module:
Step Description
1 The Master driver obtains configuration data from the Flash area of the module. The
configuration data obtained includes the number of commands and the Master Command
List. These values are used by the Master driver to determine the type of commands to
be issued to the other nodes on the DNP network.
2 After configuration, the Master driver begins transmitting read and/or write commands to
the other nodes on the network. If writing data to another node, the data for the write
command is obtained from the module’s internal database to build the command.
3 Presuming successful processing by the node specified in the command, a response
message is received into the Master driver for processing.
4 Data received from the node on the network is passed into the module’s internal
database, assuming a read command.
5 Status is returned to the processor for each command in the Master Command List.
Care must be taken in constructing each command in the list for predictable
operation of the module. If two commands write to the same internal database
address of the module, the results will not be as desired. All commands
containing invalid data are ignored by the module.