Siemens SIMATIC ET 200AL System Manual page 1104

The following figure shows a digital input module with the basic submodule and three MSI
submodules. Each submodule is assigned to an IO controller. Diagnostics and parameter
assignment of the digital input module can be performed from the IO controller 1 via the
basic submodule.
①
②
Figure 5-30
Value status (Quality Information, QI)
The meaning of the value status depends on the submodule to which it pertains.
With basic submodule (= 1st submodule), the "0" value status indicates that the value is
incorrect.
With an MSI submodule (2nd to 4th submodule), the "0" value status indicates that the value
is incorrect or the basic submodule has not yet been configured (not ready).
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Parameter assignment and system diagnostics
DI module with MSI submodules
Functions
5.3 Shared device
157