Siemens SIMATIC S7-1500 Manual page 35

Value status (Quality Information, QI)
The meaning of the value status depends on the submodule on which it occurs.
For the 1st submodule (= basic submodule), the value status 0 indicates that the value is
incorrect.
For the 2nd to 4th submodule (=MSI submodule), the value status 0 indicates that the value
is incorrect or the basic submodule has not yet been configured (not ready).
The figure below shows the assignment of the address space with submodules 1 and 2.
Figure 4-6
Analog Input Module AI 4xU/I/RTD/TC ST (6ES7531-7QD00-0AB0)
Manual, 09/2016, A5E32366209-AC
Address space for configuration as 1 x 4-channel AI 4xU/I/RTD/TC ST MSI with value
status
Parameters/address space
4.4 Address space
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