Technical data

152 • MODBUS Functions
Description of the MODBUS Functions
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
6.3.5 Function Code FC5 (Write Coil)
This function writes a single output bit to the slave device.
Request
The request specifies the reference number (output address) of output bit to be
written. The reference number of the request is zero based; therefore, the first
coil starts at address 0.
Example: Turn ON the second output bit (address 1):
Byte Field name Example
Byte 0, 1 Transaction identifier 0x0000
Byte 2, 3 protocol identifier 0x0000
Byte 4, 5 length field 0x0006
Byte 6 unit identifier 0x01 not used
Byte 7 MODBUS function code 0x05
Byte 8, 9 reference number 0x0001
Byte 10 ON/OFF 0xFF
Byte 11 0x00
Response
Byte Field name Example
.....
Byte 7 MODBUS function code 0x05
Byte 8, 9 Reference number 0x0001
Byte 10 Value 0xFF
Byte 11 0x00
Exception
Byte Field name Example
.....
Byte 7 MODBUS function code 0x85
Byte 8 Exception code 0x01, 0x02 or 0x03