| Function code | Name | Description |
|---|---|---|
| 01 |
Illegal function |
The server does not support the requested function. |
| 02 |
Illegal data address |
The server does not support the data address or the number of items in the query is incorrect. |
| 03 |
Illegal data value |
A value contained in the query data field is out of range. |
| 04 | Server device error | This exception only occurs when a Modbus instance is activated without proper initialization. A relay restart is required. |