Allen-Bradley 825-P, User Manual

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Rockwell Automation Publication 825-UM004D-EN-P - November 2012 139
Modbus RTU Communications Chapter 10
The relay responses to errors in the query are shown below:
Table 73 - 10h Preset Multiple Registers Query Error Messages
60h Read Parameter
Information Command
The 825-P uses this function to allow a Modbus master to read parameter
information from the relay. One parameter (setting) is read in each query.
Table 74 - 60h Read Parameter Information Command
The Parameter Descriptor field is defined in Table 75:
2 bytes Starting Address
2 bytes Number of Registers
2 bytes CRC-16
Error Error Code Returned Communication 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 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
Bytes Field
Bytes Field
Requests 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
A successful response from the slave will have the following format:
1 byte Slave Address
1 byte Function Code (60h)
2 bytes Parameter Number
1 byte Parameter Descriptor
1 byte Parameter Conversion
2 bytes Parameter Minimum Settable Value
2 bytes Parameter Maximum Settable Value
2 bytes Parameter Default Value
2 bytes CRC-16