Error codes (hex)

Name

Meaning

01

Illegal Function

Use of a function code that is not supported

02

Illegal Data Address

Use of an invalid storage address or attempt to write to a read-only address

03

Illegal Data Value

Use of illegal data values, e.g. a non-permitted number of registers

04

Slave Device Failure

Unrecoverable failure

05

Acknowledge

The server needs a long time for processing the request. It sends an acknowledge in order to prevent a timeout of the client.

06

Slave Device Busy

Currently, the device cannot process Modbus commands

0A

Gateway Path Unavailable

Gateway is overloaded or configured incorrectly

0B

Gateway Target Device Failed to Respond

Error message of the gateway: No answer from the addressed device