KROHNE UFC 400 Modbus EN - Manual (Page 26)

7
TROUBLESHOOTING
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UFC 400
www.krohne.com 05/2013 - 4002744801 - AD Modbus UFC 400 R01 en
7.4 Responding with exception "Illegal Data Address"
There are four reasons why the signal converter will return an "Illegal Data Address" error
message when the master device makes a request.
a) The register address being requested is not supported by the signal conveter, check the
requested register against the registers specified in the section "Parameters".
b) Although the start address is valid, when accessing multiple registers the number of registers
requested may extend beyond the end of the valid address range for that group of variables.
Check the number of variables requested and ensure that the last register address is valid.
c) The number of registers requested is not correct for the data type being requested. For
example, if registers containing floating point variables are requested then the number of
requested registers must be a multiple of 2 as the floating point variables are held in two
consecutive registers. For double precision floating point variables the number of registers
requested must be a multiple of 4.
d) From c) above, the system will respond with an "Invalid Address" error when an attempt is
made to access the associated registers of a multi-register variable, for example when access to
the second register of a floating point variable is attempted. i.e. if an attempt is made to access
Input register 30001, which contains the second half of the variable accessed by Input register
30000.
7.5 Responding with exception "Illegal Data Value"
When the signal converter responds with an "Illegal Data Value", it is because the value being
written to a holding register in the signal converter is beyond the permitted limits for that
register. The limits for each holding register are indicated in the section "Parameters".