Schweitzer Engineering Laboratories SEL-587Z - 07 h Read Exception Status Command

D.9
Date Code 20020903 SEL-587Z Instruction Manual
Modbus RTU Communications Protocol
Modbus Commands
The command response is identical to the command request.
The relay responses to errors in the query are shown below:
07h Read
Exception
Status Command
The SEL-587Z uses this function to allow a Modbus master to read the present
status (get a “snapshot” view) of the relay and protected circuit by reading
eight predefined status bits.
Table D.10 06h Preset Single Register Command
Bytes Field
Requests 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
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
Table D.11 07h Read Exception Status Command
Bytes Field
Requests from the master must have the following format:
1 byte Slave Address
1 byte Function Code (07h)
0 bytes No Data Fields Are Sent
2 bytes CRC-16
A successful response from the slave will have the following format:
1 byte Slave Address
1 byte Function Code (07h)
1 byte Status Byte
2 bytes CRC-16
The status byte is sent most significant bit first, and consists of the following bits:
Bit 0 OUT4 Status
Bit 1 OUT3 Status
Bit 2 OUT2 Status
Bit 3 OUT1 Status
Bit 4 Alarm Output status
Bit 5 Input 2 Status
Bit 6 Input 1 Status
Bit 7 Relay Status