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7. Modbus
7.1
About
The SGC controller supports a custom protocol based on the standard Modbus over an RS-485 layer. The controller
operates in a server mode and responds to commands received from an external Modbus client.
This document will only describe the information required to communicate with the controller using the Modbus protocol.
For more information about Modbus in general and the Modbus protocol, refer to the documentation freely available at
http://www.modbus.org.
Refer to the Modbus tables, available for download at www.deif.com, to see how the controller data is mapped to the
Modbus addresses.
7.2
Modbus connection details
The controller uses Modbus RTU as the transmission mode.
Connection details
• Start bit: 1
• Data bits: 8
• Parity: None
• Stop bit: 1
• Cyclic Redundancy Check (CRC)
Setting up Modbus communication
• Find the server ID from the SMPS and configure the same ID in the controller.
• Enable the controller in the configuration of the SMPS after hardware connections are made.
• Connect the controller terminals 16 and 15 to the SMPS terminals A and B.
• Use a two-core shielded cable for connection.
• Use wires with different colours for terminals 16 and 15.
• Connect the wires correctly to make sure they do not get short with other wires.
• Do not use multi-strand wires for the connection.
7.3
Modbus communication settings
RS-485 communication settings
• Server ID: 1 to 247
• Baud rate: 1200/2400/4800/9600/19200/38400/57600/115200 bps
• Parity: None/Even/Odd
• Stop bit: 1, 2
• Recommended polling frequency: 50 Hz
• No response timeout: 250 ms
Command from Modbus server for function 16
Byte
Field
0
Server address
1
Function code (0x10)
2
First register address - high byte
3
First register address - low byte
User manual 4189341340A EN
Comments
As configured in the controller.
16-bit register address, register address map is
described in the Register map.
Page 65 of 76
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