Siemens SINAMICS V20 Inverter, Operating Instructions Manual

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Communicating with the PLC
7.2 MODBUS communication
SINAMICS V20 Converter
Operating Instructions, 10/2019, A5E34559884-012
185
Response for unsuccessful write operation - write request still not completed
Value Byte Description
11 h 1 Slave address
03 h
20 h
0001 h
2F00 h
0004 h
2
3
4,5
6,7
8,9
Function code (read)
Number of following data bytes (20 h: 32 bytes
≙
16 regis-
ters)
40601: DS47 Control = 1 (request is processed)
40602: Function 2F h(47), response length 0 (fault)
40603: Error code: 0004 Response Not Ready (response has
still not been issued)
xx h
xx h
10
11
CRC "Low"
CRC "High"
Exception Responses
If an error is detected through the MODBUS processing, the slave will respond with the FC
of the request, but with most significant bit of the FC high and with the Exception Code in the
data field. However, any error detected on the global address 0 does not result in a response
since all slaves cannot respond at once.
If an error is detected within the received message (for example, parity error, incorrect CRC
and so on), then NO response is sent to the master.
Note that if a request with FC16 is received which contains a write that the converter cannot
perform (including write to a zero entry), other valid writes will still be performed even though
an exception response is returned.
The following MODBUS Exception Codes are supported by SINAMICS V20:
Exception Code MODBUS name Meaning
01 Illegal function code The function code is not supported – only FC3, FC6 and
FC16 are supported.
02 Illegal data address An invalid address was queried.
03 Illegal data value An invalid data value was recognized.
04 Slave device failure An unrecoverable error occurred while the device was
processing the action.
The table below shows the cases in which an Exception Code is returned:
Error description Exception Code
Unknown Function Code 01
Read registers, which are out of boundary 02
Write register, which is out of boundary 02
Read request of too many registers (>125) 03
Write request of too many registers (>123) 03
Incorrect message length 03
Write to a read-only register 04
Write register, error in parameter access 04
Read register, error in Parameter Manager 04
Write to a zero entry 04
Unknown error 04