Communication Procedure - Siemens SINAMICS S120 Function Manual

Communication
11.4 Communication via MODBUS TCP
Table 11- 34 Response for successful write operation
Value Byte Description
MBAP header
Number of following data bytes (20 h: 32 bytes ≙ 16 registers)
03 h 7 Function code (read)
20 h 8
0002 h 9,10 40601: DS47 Control = 2 (request was executed)
2F04 h 11,12 40602: Function code 2F h (47), response length 4 bytes
8002 h 13,14 40603: Request reference mirrored = 80 h,
response identifier = 2 (change parameter)
0101 h 15,16 40604: DO-ID = 1, number of parameters = 1
Table 11- 35 Response for unsuccessful write operation - write request still not completed
Value Byte Description
MBAP header
Number of following data bytes (20 h: 32 bytes ≙ 16 registers)
03 h 7 Function code (read)
20 h 8
0001 h 9,10 40601: DS47 Control = 1 (request is processed)
2F00 h 11,12 40602: Function 2F h(47), response length 0 (fault)
0004 h 13,14 40603: Error code:
issued)
11.4.7

Communication procedure

Logical error
If the device detects a logical error within a request, it responds to the controller with an
"exception response". In the response, the device sets the highest bit in the function code to
1. If the device receives, for example, an unsupported function code from the controller, the
device responds with an "exception response" with code 01 (illegal function code).
Table 11- 36 Overview of exception codes
Exception
code
01
02
03
04
870
0004 Response Not Ready (response has still not been
Modbus name
Illegal function code
Illegal Data Address
Illegal data value
Server failure
Remark
An unknown (unsupported) function code was sent to the
device.
An invalid address was requested.
An invalid data value was detected.
The device has terminated during processing.
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
Drive functions