4/2016

SATEL technical bulletin

SATELLAR

SATELLAR Protocols

Example 1. : DNP3 with TCP, UDP and serial port

In this example, SATELLARs are used to enable DNP3 communication between a Supervisory Control And

Data Acquisition (SCADA) device and two Remote Terminal Units (RTU). The SCADA is connected to SATELLAR

R1 with an Ethernet cable, and the two RTUs to their SATELLARs with a serial cable. SATELLAR R1 has radio

connectivity to both R2 and R3, and there can be repeaters between. The setup can be seen in gure down

message to the SCADA, it is written to the serial port of R2. R2 will send it as a UDP packet to R1, which will in

turn write the message to the SCADA through the open TCP connection.

Device IP Address RMAC Address DNP3 Address

SCADA 192.168.1.100 255

R1 192.168.1.1 1

R2 192.168.2.1 2

R3 192.168.3.1 3

RTU A 2

RTU B 3

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devices have destination ports 2005 and R1 has listening port 2005.

Both slave SATELLARs’ RMAC addresses match the DNP3 addresses of the RTUs, so R1 can use Application

Address to RMAC Address Mapping. Messages sent to the DNP3 address 2 will be routed rst to R2, and then

to RTU A. Because the SCADA’s address is 255, both slaves need to use manual mapping. They both need just

one Address Mapping Row: 255 192.168.1.1

This means that the DNP3 messages to the destination address 255 will be routed to R1, which will in turn

relay the message to the SCADA.

Variations to the example

The example uses UDP to send the messages over the radio. This is generally recommended, since UDP uses

less radio resources than TCP and is also faster. But if a slower but more secure connection is desired, TCP

were also connected to the slave devices through Ethernet, then both R2 and R3 would need to change the

Application Transport Protocol to TCP and also set a port that the RTUs could use. No other settings need to

be changed.

The protocol could be changed to Modbus RTU, IEC101 or Custom Protocol and it would function exactly the

same way.

Device R1 R2 R3

Application Protocol DNP3 DNP3 DNP3

Application Transport Protocol TCP Serial Port Serial Port

Application Listening Port 20000 (No eect) (No eect)

Serial Port (No eect) RS-232 RS-232

Address Mapping Application Address to

RMAC

Manual Manual

Address Mapping Row (empty) 255 192.168.1.1 255 192.168.1.1

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Example 2: Modbus TCP and Modbus TCP/RTU conversion

This example uses the same network topology as the example 1, but this time the SCADA and the RTU A use

Modbus TCP and the RTU B uses Modbus RTU. This example shows how to congure the SATELLAR devices

so that the SCADA only needs to query R1 with Modbus TCP to get replies from RTU A and B.

The addresses of the dierent devices look like this:

R1 will be congured to route Modbus TCP to both substations. Because RTU A uses Modbus TCP, the target

IP address is the address of the RTU. RTU B uses Modbus RTU, so the target IP is the address of R3. R3 will

When the SCADA sends a Modbus message to the RTU A, it will rst be received by the R1. It analyzes the

destination address and opens a TCP connection to the RTU A. The reply will be sent back to the SCADA

through the open TCP connection. The R2 only routes the IP packets without any analysis.

When the SCADA sends a Modbus message to the RTU B, the R1 will route the TCP connection to the R3. The

R3 will receive the message, convert it to Modbus RTU and write it out of the serial port.

Device IP Address RMAC Address Modbus Address

SCADA 192.168.1.100 1

R1 192.168.1.1 1

R2 192.168.2.1 2

R3 192.168.3.1 3

Serial Port (No eect) RS

Transport Protocol For Substation Data TCP TCP

Destination Port For Substation Data 502 (No eect)

Listening Port For Substation Data (No eect) 502

Address Mapping Manual Point-to-point

Address Mapping Table 2 192.168.2.2

3 192.168.3.1

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