Siemens Sinamics G120P Operating Instructions Manual page 240

Operation
6.8 Communication via RS485
Communication error
If the slave detects a communication error on receipt (parity, CRC), it does not send a
response to the master (this can lead to "setpoint timeout").
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 6- 28
Exception
code
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
"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 "Setpoint timeout" only applies for access to process data (40100, 40101, 40110,
40111). The "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.
240
Overview of exception codes
Modbus name
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.
Operating Instructions, 12/2014, A5E32923362A
Inverter cabinet units