User manual

IEC61131 User and Reference Manual
April 22, 2008
470
SCADAPack DNP Address Mapping
Address mapping provides a direct link between an outstation’s DNP points and local Modbus
registers within the SCADAPack DNP master. These remote DNP points are now mapped into
specific regions of the DNP master’s Modbus database.
When DNP data points are received from an outstation, a cross reference to the address mapping
table is made, and if a match is found, the DNP data will be written to the corresponding local
Modbus register. 'Input' DNP object types from the outstation are mapped to the master’s local input
Modbus register space 1xxxx or 3xxxx. These local Modbus registers are updated after the
corresponding DNP point gets updated; usually by a class poll to the outstation, or if the outstation
issues an unsolicited response based on a change of value or state on these points.
‘Output' DNP object types from the outstation are mapped to the master’s local output Modbus
register space 0xxxx or 4xxxx. Changes made to the local Modbus register will trigger a DNP Write
message, with the current point value, to the outstation. DNP Write implemented in SCADAPack
controllers requires an Application Layer confirmation from the target outstation.
By configuring the Address Mapping table, outstation DNP points are therefore mapped to local
Modbus registers. As mapped local Modbus points, the data is available for use in application
programs such as TelePACE and ISaGRAF. In addition a Modbus SCADA Host can poll the
SCADAPack master for these points.
The following diagram shows a simple DNP Address Mapping network.
SCADAPack 32
Modbus DNP3
Slave Master
SCADAPack
Outstation A
SCADAPack
Outstation B
SCADA Host
Modbus Master
Figure 0-5: SCADAPack Address Mapping
In this network the SCADAPack master updates is local database with mapped outstation data. The
manner and frequency with which the SCADAPack master updates the local Modbus registers,
depends on the number and type of I/O object types the registers are mapped to.
This feature is limited to the SCADAPack 32, SCADAPack 330/334, SCADAPack 350 and
SCADASense 4203 controllers.
Note: Mapping numerous local Modbus output registers (0xxxx and 4xxxx), to a remote
DNP device may cause frequent communications between the master and the slave,
if the associated registers are being changed frequently in the master. On limited
DNP Master Address Mapping
Local Modbus Register
11001
11002
DNP Outstation
DNP Point
1
2