7.8.10 Function Codes Supported by Modbus RTU
Modbus RTU supports use of the following function codes in the function
field of a message:
Function
Function Code
Read coils
1 hex
Read holding registers
3 hex
Write single coil
5 hex
Write single register
6 hex
Write multiple coils
F hex
Write multiple registers
10 hex
Get comm. event counter
B hex
Report slave ID
11 hex
Function
Function Code
Sub-function code
Sub-function
Diagnostics
8
1
Restart communication
2
Return diagnostic register
10
Clear counters and diagnostic register
11
Return bus message count
12
Return bus communication error count
13
Return bus exception error count
14
Return slave message count
7.8.11 Database Error Codes
In the event of an error, the following error codes may appear in the data field of a response message. For a full explanation of the structure of an
exception (i.e. error) response, please refer to the section
Modbus RTU Message Framing Structure, Function Field.
Error Code in data field
(decimal)
Database Error Code description
00
The parameter number does not exit
01
There is no write access to the parameter
02
The data value exceeds the parameter limits
03
The sub-index in use does not exit
04
The parameter is not of the array type
05
The data type does not match the parameter called
06
Only reset
07
Not changeable
11
No write access
17
Data change in the parameter called is not possible in the present mode
18
Other error
64
Invalid data address
65
Invalid message length
66
Invalid data length or value
67
Invalid function code
130
There is no bus access to the parameter called
131
Data change is not possible because factory set-up is selected
7 RS-485 Installation and Set-up
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®
AQUA Drive Design Guide
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