Siemens SINAMICS G120 Operating Instructions Manual page 178

Configuring the fieldbus
7.7 Communication via RS485
Logical error
If the slave detects a logical error within a request, it responds to the master with an
"exception response". In this case, the slave sets the highest bit in the function code to 1 in
the response. If, for example, it receives an unsupported function code from the master, the
slave responds with an "exception response" with code 01 (illegal function code).
Table 7- 25
Exception code Modbus name
01
02
03
04
Maximum processing time, p2024[0]
The slave-response time is the time in which the Modbus master expects a response to a
request. Set the same slave-response time (p2024 [0] in the inverter) in the master and
slave.
Process data monitoring time (setpoint timeout), p2040
The alarm "Setpoint timeout" (F1910) is issued by the Modbus if p2040 is set to a value > 0
ms and no process data is requested within this time period.
The alarm "Setpoint timeout" only applies for access to process data (40100, 40101, 40110,
40111). The alarm "Setpoint timeout" is not generated for parameter data (40200 ... 40522).
Note
Adjust the time (factory setting = 100 ms) depending on the number of slaves and the baud
rate set on the bus.
178
Overview of exception codes
Illegal function code
Illegal Data Address
Illegal data value
Server failure
Remark
An unknown (unsupported) function code was sent to the
slave.
An invalid address was requested.
An invalid data value was detected.
Slave has terminated during processing.
Converter with the CU250S-2 Control Unit (vector)
Operating Instructions, 06/2013, FW V4.6, A5E31759476B AB