Siemens SIRIUS 3RW5 - Exception Codes; Error Responses

Messages and diagnostics
7.3 Exception Codes
SIRIUS 3RW5 Modbus communication module
112 Equipment Manual, 03/2020, A5E43676481002A/RS-AC/003
7.3 Exception Codes
7.3.1 Error Responses
Operating principle
If the Modbus TCP server or the Modbus RTU slave detects an error in the request telegram
of the Modbus TCP Client or the Modbus RTU master, e.g. register address not permitted,
the Modbus TCP server or the Modbus RTU slave will permit the most significant bit in the
Function Code of the response telegram: Requested Function Code + 0x80. This step is
followed by transmission of a byte with the Exception Code that describes the cause of the
error.
Typical Exception Code telegram
The Exception Code telegram of the Modbus TCP server or Modbus RTU slave has the
following structure, for example:
● Address Field or slave address: The address of the 3RW5 soft starter is not entered in
the example (-).
● Requested Function Code: 5 (= 0x05)
● Exception Code: 2 (= 0x02)
● The CRC CHECK is not entered in the example (-).
Response telegram from the Modbus TCP server:
Address Field
Function Code
Exception Code
7 bytes
1 byte
1 byte
-
0x85
0x02
Response telegram from the Modbus RTU slave:
Slave address
Function Code
Exception Code
CRC
1 byte
1 byte
1 byte
2 bytes
-
0x85
0x02
-