User Manual

Operation
RFI-9256 Radio Modem User Manual Page 32 of 96
 TDE
PROTOCOL ROUTING
The protocol decoder for the packet based SCADA protocols extracts the destination remote terminal unit
(RTU) address from the protocol and maps it to a radio address. This routing scheme is shown in Figure 8.
Controller
RFI
-
9256
Master
Main
RFI
-
9256
Slave
Addr=1000
RTU
Main
SCADA Data Address SCADA Data Pad Pad
Table
SCADA
Address
Slave Address
Figure 8: SCADA protocol routing
The SCADA protocol routing table on the RFI-9256 can have four types of entries.
 Default route. This route is mostly used by slaves and is a required entry for any slave in a
protocol network. This route only requires the address of the destination radio. This route is used
when no other route can be matched in the routing table. On slave units this destination address
must always be the address of the master unit.
 Single route. This route explicitly maps a single RTU address to a radio address. If a single route
exists, then it overrides any matching mapped route or range route.
 Mapped route. This route maps a relationship between RTU addresses and radio addresses. This
is an efficient method of describing a network providing the RTUs and radios are numbered
sequentially. This route configuration requires an RTU address to be assigned as the base for the
route and an RTU address to define the range of addresses to be used by the route. It also requires
a radio address associated with the base RTU address.
The decoder subtracts the RTU base address from each decoded RTU address. This result is then
added to the radio base address. Consider the situation shown in Figure 9.