Descriptions of functions
10.8 Communication via Modbus TCP
SINAMICS DCM DC Converter
Operating Instructions, 12/2018, A5E34763375A
549
10.8.6
Communication sequence
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 10- 64 Overview of exception codes
Exception
code
Modbus name
Remark
01
Illegal function code
An unknown (unsupported) function code was sent to the
device.
02
Illegal Data Address
An invalid address was requested.
03
Illegal data value
An invalid data value was detected.
04
Server failure
The device has terminated during processing.
Process data monitoring time (setpoint timeout)
The "Setpoint timeout" only applies for access to process data (40100 ... 40109, 40110 ...
40119). The "Setpoint timeout" is not generated for parameter data (40300 … 40522).
Fieldbus interface:
In parameter p2040 you define the time for cyclic data exchange for process data.
Setting range 0 - 2000 s.
The time depends on the amount of data to be transferred and the control.
"Setpoint timeout" (F01910) is issued by the Modbus if p2040 is set to a value > 0 ms and no
process data is requested within this time period.
COMM BOARD:
In parameter p8840 you define the time for cyclic process data exchange.
Setting range 0 - 2000 s.
The time depends on the amount of data to be transferred and the control.
"Setpoint timeout" (F08501) is issued by the Modbus if p8840 is set to a value > 0 ms and no
process data is requested within this time period.
