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 VLT
®
AQUA Drive Design Guide
7-18
MG.20.N5.22 - VLT
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