Messages and diagnostics
7.3 Error codes
SIRIUS 3RW5 Modbus TCP communication module
Manual, 03/2018, A5E43676481002A/RS-AA/001
61
Exception Responses
Operating principle
When the server detects an error in the request telegram from the client (illegal register
address, for example), the server sets the highest value bit in the function code of the
response telegram: Requested function code + 80h. This step is followed by transmission of
a byte with the Exception Code that describes the cause of the error.
Typical exception code frame
The exception code telegram from the server has the following structure, for example:
● Address Field: The address of the 3RW5 Soft Starter is not entered in the example (-).
● Requested Function Code: 5
● Exception code: 2
Response telegram from server:
Meaning in
accordance with
Modbus specification
1 (= 0x01) Illegal function Illegal
function code
The requested function code is not supported. Pay particular attention
to chapter Function Codes (Page 51).
2 (= 0x02) Illegal data address Illegal bit or
register
address on
Address does not exist. For functions that work with an addressing
range, all addresses affected by the request are checked.
3 (= 0x03) Illegal data value Server has
illegal data
The number of addresses is not correct. The number of parameters for
the requested function was too high (or 0)
4 (= 0x04) Failure in associated
Server has
There is an unspecified server error that prevented execution of the
6 (= 0x06) Busy, rejected
message
Server is not
ready to
The device is busy and unable to process the request at this time. This
can occur following a parameterization operation via Modbus when the
new parameter values are transferred to the device.
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