E.2
SEL-700G Relay
Instruction Manual
Date Code 20170814
Modbus RTU Communications
Communications Protocol
The SEL-700G SLAVEID setting defines the device address. Set this value to
a unique number for each device on the Modbus network. For Modbus
communication to operate properly, no two slave devices can have the same
address.
The cyclical redundancy check detects errors in the received data. If the relay
detects an error, it discards the packet.
Modbus Responses
The slave device sends a response message after it performs the action the
query specifies. If the slave cannot execute the query command for any reason,
it sends an error response. Otherwise, the slave device response is formatted
similarly to the query and includes the slave address, function code, data (if
applicable), and a cyclical redundancy check value.
Supported Modbus
Function Codes
The SEL-700G supports the Modbus function codes shown in Table E.2.
Table E.2
SEL-700G Modbus Function Codes
Codes
Description
01h
Read Discrete Output Coil Status
02h
Read Discrete Input Status
03h
Read Holding Registers
04h
Read Input Registers
05h
Force Single Coil
06h
Preset Single Register
08h
Diagnostic Command
10h
Preset Multiple Registers
60h
Read Parameter Information
61h
Read Parameter Text
62h
Read Enumeration Text
7Dh
Encapsulate Modbus Packet With Control
7Eh
NOP (can only be used with the 7Dh function)
Summary of Contents for SEL-700G Series
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