E.12
SEL-751 Relay Instruction Manual Date Code 20170927
Modbus RTU Communications
Communications Protocol
10h Preset Multiple
Registers Command
This function code works much like code 06h, except that it allows you to
write multiple registers at once, as many as 100 per operation. If you are
accustomed to 4X references with the function code, for six-digit addressing,
simply add 400001 to the standard database addresses.
The relay responses to errors in the query are as follows.
60h Read Parameter
Information
Command
The SEL-751 uses this function to allow a Modbus master to read parameter
information from the relay. One parameter (setting) is read in each query.
Table E.20 10h Preset Multiple Registers Command
Bytes Field
Queries from the master must have the following format:
1 byte Slave Address
1 byte Function Code (10h)
2 bytes Starting Address
2 bytes Number of Registers to Write
1 byte Number of Bytes of Data (n)
n bytes Data
2 bytes CRC-16
A successful response from the slave will have the following format:
1 byte Slave Address
1 byte Function Code (10h)
2 bytes Starting Address
2 bytes Number of Registers
2 bytes CRC-16
Table E.21 10h Preset Multiple Registers Query Error Messages
Error Error Code Returned
Communications
Counter Increments
Illegal register to set Illegal Data Address (02h) Invalid Address
Illegal Write
Illegal number of registers to set Illegal Data Value (03h) Illegal Register
Illegal Write
Incorrect number of bytes in
query data region
Illegal Data Value (03h) Bad Packet Format
Illegal Write
Invalid register data value Illegal Data Value (03h) Illegal Write
Table E.22 60h Read Parameter Information Command (Sheet 1 of 2)
Bytes Field
Queries from the master must have the following format:
1 byte Slave Address
1 byte Function Code (60h)
2 bytes Parameter Number
2 bytes CRC-16
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