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Crescendo VHF Half-Duplex User Manual Page 51 of 74
7.4 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 2ms has been used on the main port of
each unit. See section 4.3.2 on page 18 for more information on packetiser timers.