Schweitzer Engineering Laboratories SEL-787, Instruction Manual, Page: 429 / 564

E.15
Date Code 20081022 Instruction Manual SEL-787 Relay
Modbus RTU Communications
Communications Protocol
61h Read Parameter
Text Command
The SEL-787 uses this function to allow a Modbus master to read parameter
text from the relay. One parameter text (setting name) is read in each query.
The relay responses to errors in the query are shown below.
62h Read
Enumeration
Text Command
The SEL-787 uses this function to allow a Modbus master to read parameter
enumeration or bit enumeration values (setting lists) from the relay. One
parameter enumeration is read in each query.
Table E.24 61h Read Parameter Text Command
Bytes Field
Queries from the master must have the following format:
1 byte Slave Address
1 byte Function Code (61h)
2 bytes Parameter Number
2 bytes CRC-16
A successful response from the slave will have the following format:
1 byte Slave Address
1 byte Function Code (61h)
2 bytes Parameter Number
16 bytes Parameter Text (setting name)
4 bytes Parameter Units (e.g., Amps)
2 bytes CRC-16
Table E.25 61h Read Parameter Text Query Error Messages
Error Error Code Returned
Communication
Counter Increments
Illegal parameter to read Illegal Address (02h) Invalid Address
Table E.26 62h Read Enumeration Text Command
Bytes Field
Queries from the master must have the following format:
1 byte Slave Address
1 byte Function Code (62h)
2 bytes Parameter Number
1 byte Enumeration Index
2 bytes CRC-16
A successful response from the slave will have the following format:
1 byte Slave Address
1 byte Function Code (62h)
2 bytes Parameter Number
1 byte Enumeration Index
16 bytes Enumeration Text
2 bytes CRC-16