Modbus error response

When the user sends the slave either a request or information that the coupler does not understand, the slave responds with an error report. This answer contains the function and the error code. 0x80 is added to the value returned by the function.

Code

Name

Meaning

1

ILLEGAL  FUNCTION

Modbus function not implemented

2

ILLEGAL DATA ADDRESS

Invalid address or length

3

ILLEGAL DATA VALUE

Invalid parameters
- Diagnostics functions
- Wrong register

4

SLAVE DEVICE ERROR

Watchdog or K-bus error