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Crescendo UHF Half-Duplex User Manual Page 52 of 78
7.4 Modbus/DNP Networks
7.4.1 Basic Modbus RTU Network with Repeater
A Modbus network with repeater is shown in Figure 21.
Crescendo
Base
1000
Crescendo
Remote
1001
Main
RTU BASE
RTU 2
RADIO CONFIGURATION
Rx Address: 1001
Repeaters in Network: 1
Max Packet Size: 267
PROTOCOL CONFIGURATION
Main Port: Modbus RTU
PROTOCOL MAPPING
Grouped 1-247 to 1000
SERIAL CONFIGURATION
Main Port: 19200, 8N1, 2ms RX Timer
Main
Crescendo
Repeater
2000
RADIO CONFIGURATION
Rx Address: 2000
Store and Forward Repeater: True
Repeaters in Network: 1
Max Packet Size: 267
PROTOCOL CONFIGURATION
Main Port: Modbus RTU
PROTOCOL MAPPING
Grouped 1-247 to 1000
SERIAL CONFIGURATION
Main Port: 19200, 8N1, 2ms RX Timer
RTU 3
Main
Crescendo
Remote
2001
RTU 4
RADIO CONFIGURATION
Rx Address: 2001
Repeaters in Network: 1
Max Packet Size: 267
PROTOCOL CONFIGURATION
Main Port: Modbus RTU
ROUTING TABLE
Route 1000-1099 to 2000
PROTOCOL MAPPING
Grouped 1-247 to 1000
SERIAL CONFIGURATION
Main Port: 19200, 8N1, 2ms RX Timer
Main
RADIO CONFIGURATION
Rx Address: 1000
Repeaters in Network: 1
Max Packet Size: 267
PROTOCOL CONFIGURATION
Main Port: Modbus RTU
ROUTING TABLE
Route 2000-2099 to 2000
PROTOCOL MAPPING
Single 2 to 1001
Mapped 3-4 to 2000
SERIAL CONFIGURATION
Main Port: 19200, 8N1, 2ms RX Timer
Figure 21: Modbus network with repeater
In order to support the ModBus protocol, an RX packetiser timer of 2 ms has been used on the main port of
each unit (see section 4.3.2 on page 18 for more information on packetiser timers).