G.6
SEL-551 Relay Instruction Manual Date Code 20110408
Modbus RTU Communications Protocol
Modbus RTU Communications Protocol
The relay responses to errors in the query are shown below:
05h Force Single Coil
Command
Use function code 05h to set or clear a coil.
The command response is identical to the command request.
The coil numbers supported by the SEL-551 are listed in Table G.9. The
physical coils (coils 1–5) are self resetting. Pulsing a set remote bit clears the
remote bit.
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
Table G.8 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
Table G.9 SEL-551 Command Coils (Sheet 1 of 2)
Coil Field
1OUT1
2OUT2
3OUT3
4OUT4
5ALARM
6 RB1
7 RB2
8 RB3
9 RB4
10 RB5
11 RB6
12 RB7
13 RB8
14 Pulse RB1
15 Pulse RB2
16 Pulse RB3
17 Pulse RB4
18 Pulse RB5
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