WAGO-I/O-SYSTEM 750
Fieldbus Communication 231
750-880, 750-880/025-000 ETHERNET Programmable Fieldbus Controller
Manual
Version 1.0.1
12.2.3.6 Function Code FC6 (Write Single Register)
This function writes the value of one single output register to a slave device in
word format.
Request
The request specifies the reference number (register address) of the first output
word to be written. The value to be written is specified in the “Register Value”
field. The reference number of the request is zero based; therefore, the first
register starts at address 0.
Example: Write a value of 0x1234 to the second output register
Table 108: Request of Function code FC6
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 0x06
Byte 8, 9
Reference number
0x0001
Byte 10, 11
Register value
0x1234
Response
The reply is an echo of the inquiry.
Table 109: Response of Function code FC6
Byte
Field name
Example
...
Byte 7
MODBUS function code 0x06
Byte 8, 9
Reference number
0x0001
Byte 10, 11
Register value
0x1234
Exception
Table 110: Exception of Function code FC6
Byte
Field name
Example
...
Byte 7
MODBUS function code 0x85
Byte 8
Exception code
0x01 or 0x02
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