Schweitzer Engineering Laboratories SEL-751 - Table E.25 Responses to 60 H Read Parameter Information Query Errors; Table E.26 61 H Read Parameter Text Command

E.14
SEL-751 Relay Instruction Manual Date Code 20170927
Modbus RTU Communications
Communications Protocol
Use Equation E.1 to calculate the actual (not scaled) value of the parameter
(setting):
Equation E.1
Use Equation E.2 to calculate the scaled setting value:
Equation E.2
The relay response to errors in the query are shown Table E.2 5 .
61h Read Parameter
Text Command
The SEL-751 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.
10 Enumeration 1 1 0 1
11 Bit Enumeration 1 1 0 1
Table E.25 Responses to 60h Read Parameter Information Query Errors
Error Error Code Returned
Communications
Counter Increments
Illegal parameter to read Illegal Address (02h) Invalid Address
Table E.24 60h Read Parameter Conversion Field Definition (Sheet 2 of 2)
Conversion
Value
Type Multiplier Divisor Offset Base
value
ParameterValue Offset+Multiplier Base• •
Divisor
----------------------------------------------------------------------------------------------------------------------------=
value
value Divisor•
Multiplier Base•
---------------------------------------------- O f f s e t–=
Table E.26 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