Appendix
A.1 Modbus TCP
PAC2200
88 Manual, 05/2018, L1V30415167B-02
Modbus exception codes
Overview
Table A- 2 Modbus exception codes
01 Illegal Function Illegal function:
• The function code in the re-
quest is not a permissible ac-
tion for the slave.
• The slave is in a status in which
it cannot process a request of
this type. This is the case, for
example, if it has not yet been
configured and is requested to
return register values.
Check which function
codes are supported.
02 Illegal Data Address Illegal data address
This address is not permissible for
the slave. This is the case, for
example, if the combination of start
offset and transfer length is invalid.
Check the offset and the
number of registers.
03 Illegal Data Value Illegal data value:
The request contains a data value
that is not permissible for the slave.
This indicates an error in the re-
maining structure of a complex
request, e.g. an incorrect data
Check that the specified
offset and the specified
data length in the com-
mand are correct.
04 Slave Device Fail-
ure
Error in processing the data:
An indefinite error occurred when
the slave attempted to execute the
Check that the specified
offset and the specified
data length are correct.
F0 Write Protection ON The action has been rejected be-
cause the write protection is set.
Deactivate write protection.
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