Schweitzer Engineering Laboratories SEL-734 - Table F.11 04 H Read Holding Register Command; Table F.12 Responses to 04 H Read Holding Register Query Errors; Table F.13 05 H Force Single Coil Command

F.6
SEL-734 Meter Instruction Manual Date Code 20090730
Modbus RTU Communications Protocol
Modbus RTU Communications Protocol
The meter responses to errors in the query are shown Tabl e F.12.
05h Force Single Coil
Command
Use function code 05h to set or clear a coil. In Tab le F.13, the command
response is identical to the command request.
The coil numbers supported by the SEL-734 can be listed in Table F.15. The
physical coils (coils 1–7) are self-resetting. Pulsing a set remote bit clears the
remote bit.
Table F.11 04h Read Holding Register Command
Bytes Field
Requests from the master must have the following format:
1 byte Slave Address
1 byte Function Code (04h)
2 bytes Starting Register Address
2 bytes Number of Registers to Read
2 bytes CRC-16
A successful response from the slave will have the following format:
1 byte Slave Address
1 byte Function Code (04h)
1 byte Bytes of data (n)
n bytes Data
2 bytes CRC-16
Table F.12 Responses to 04h Read Holding Register Query Errors
Error Error Code Returned
Communication Counter
Increments
Illegal register to read Illegal Data Address (02h) Invalid Address
Illegal number of
registers to read
Illegal Data Value (03h) Illegal Register
Format error Illegal Data Value (03h) Bad Packet Format
Busy Slave is busy with other
task (06h)
Table F.13 05h Force Single Coil Command
Bytes Field
Requests from the master must have the following format:
1 byte Slave Address
1 byte Function Code (05h)
2 bytes Coil Reference
1 byte Operation Code (FF for bit set, 00 for bit clear)
1 byte Placeholder (00)
2 bytes CRC-16
Courtesy of NationalSwitchgear.com