WebRelay-10 Users Manual
Operation
Response
WebRelay-10 Response Frame Example – Write Coils 7-9 ON
Field Name
Length
Function
Example Data
Transaction Identifier
2 bytes
Synchronization number.
0x0001
Protocol Identifier
2 bytes
Zero for Modbus/TCP
0x0000
Message Length
2 bytes
Number of bytes in frame (below)
0x0004
Unit Identifier
1 byte
Slave Address (0xff if not used)
0xFF
Function Code
1 byte
Write Multiple Coils
0x0F
Data
4 bytes
Start address (0x0000 – 0x0009)
Relay count (0x0001 – 0x000A)
0x0006
0x0003
RX String: 00 01 00 00 00 06 FF 0F 00 06 00 03
Errors
Multiple Coil Write Error Function Code (1 Byte): 0x8F
Exception codes (1 Byte):
0x01 – Function not supported.
0x02 – Incorrect combination of start address and relay quantity
0x03 – Byte count out of range.
Error Response Frame Example
Field Name
Length
Function
Example Data
Transaction Identifier
2 bytes
Synchronization between messages of
server and client.
0x0001
Protocol Identifier
2 bytes
Zero for Modbus/TCP
0x0000
Message Length
2 bytes
Number of bytes in frame (below)
0x0003
Unit Identifier
1 byte
Slave Address (0xff if not used)
0xFF
Function Code
1 byte
Error code
0x8F
Data
1 byte
Exception code (
0x01 - 0x02
)
0x02
Rx String: 00 01 00 00 00 03 FF 8F 03
Xytronix Research & Design, Inc.
page 75
