Sel SEL-787 - Table E.15 Responses to 05 H Force Single Coil Query Errors; Table E.16 06 H Preset Single Register Command; Table E.17 Responses to 06 H Preset Single Register Query Errors

E.12
SEL-787 Relay Instruction Manual Date Code 20150130
Modbus RTU Communications
Communications Protocol
Coil addresses start at 0000 (i.e., Coil 1 is located at Coil address 0000). If the
device is disabled it will respond with error code 4 (Device Error). In addition
to Error Code 4, the device responses to errors in the query are shown in
Table E.15.
06h Preset Single
Register Command
The SEL-787 uses this function to allow a Modbus master to write directly to
a database register. Refer to the Modbus Register Map in Table E.34 for a list
of registers that can be written by using this function code. If you are
accustomed to 4X references with this function code, for six-digit addressing,
add 400001 to the standard database addresses.
In Table E.16, the command response is identical to the command required by
the master.
The relay responses to errors in the query are shown in Table E.17.
Table E.15 Responses to 05h Force Single Coil Query Errors
Error Error Code Returned
Communication Counter
Increments
Invalid bit (coil) Illegal Data Address (02h) Invalid Address
Invalid bit state requested Illegal Data Value (03h) Illegal Register
Format Error Illegal Data Value (03h) Bad Packet Format
Table E.16 06h Preset Single Register Command
Bytes Field
Queries from the master must have the following format:
1 byte Slave Address
1 byte Function Code (06h)
2 bytes Register Address
2 bytes Data
2 bytes CRC-16
Table E.17 Responses to 06h Preset Single Register Query Errors
Error Error Code Returned
Communication Counter
Increments
Illegal register address Illegal Data Address (02h) Invalid Address Illegal Write
Illegal register value Illegal Data Value (03h) Illegal Write
Format error Illegal Data Value (03h) Bad Packet Format