Modbus Configuration & Commands; Modbus Serial Configuration - Xylem ODO RTU User Manual

5. Modbus Configuration & Commands
5.1

Modbus Serial Configuration

ODO RTU operates over RS485. The serial configuration can be modified, including the baud rate, parity, and Modbus slave
address. By default, the baud rate is 9600, slave address is 0x01, and parity is even. As per the Modbus serial specification, there is
one stop bit when parity is set, and two stop bits when there is no parity. All values are big-endian byte ordered.
Slave Addresses
The slave address is set using a single register write command (function code 0x06) of address 0x0000. Addresses in range of 1 to
247 are supported. Devices will allow broadcast write access using address 0x255. The default address is 0x01.
Request
Function Code
Register Address
Register Value
Response
Function Code
Register Address
Register Value
Error
Error Code
Exception Code
The slave address can also be read using a read holding registers command (function code 0x03) of address 0x0000
Request
Function Code
Register Address
Number Registers
Response
Function Code
Byte Count
Register Value
Modbus Configuration & Commands
1 byte
2 bytes
2 bytes
1 byte
2 bytes
2 bytes
1 byte
1 bytes
1 byte
2 bytes
2 bytes
1 byte
1 byte
2 bytes
0x06
0x0000
0x0001
0x06
0x0000
0x0001
0x86
0x03 (Illegal Data Value)
0x03
0x0000
0x0001
0x03
0x02
0x0001
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