Siemens SIMATIC ET 200AL, System Manual

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Functions
5.3 Shared device
PROFINET with STEP 7
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Function Manual, 05/2021, A5E03444486-AL
MSI submodules
The input values of all channels are copied to a basic submodule and up to three other
MSI submodules during MSI configuration of an input module. The channels of the module
are then available with identical input values in the basic submodule and the MSI
submodules. The MSI submodules can be assigned to up to three IO controllers when the
module is used in a shared device. Each IO controller has read access to the same channels.
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 Read access
② Parameter assignment and system diagnostics
Figure 5-33 DI module with MSI submodules
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).