Logical error
If the slave detects a logical error within a request, it responds to the master with an "exception
response". In the response, the slave sets the highest bit in the function code to 1. If the slave
receives, for example, an unsupported function code from the master, the slave responds with
an "exception response" with code 01 (Illegal function code).
Table 6-31 Overview of exception codes
Exception
code
Modbus name Remark
01 Illegal function code An unknown (unsupported) function code was sent to the
slave.
02 Illegal Data Address An invalid address was requested.
03 Illegal data value An invalid data value was detected.
04 Server failure Slave has terminated during processing.
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 converter) 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.
6.2.3.11 Application example
An application example for MODBUS RTU is provided on the Internet:
Communication via the MODBUS interface (https://support.industry.siemens.com/cs/ww/en/
view/35928944)
Advanced commissioning
6.2 Drive control
SINAMICS G120XA converter
166 Operating Instructions, 03/2019, FW V1.0, A5E44751205B AB
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