Siemens SIMATIC ET 200AL System Manual page 103

10.5 Behavior during operation
Effect of discrepancy between station master and station option
For the online display and for the display in the diagnostics buffer (module OK or module
faulty), the station master is always used and not the differing station option.
Example: A module outputs diagnostics data. This module is configured in slot 4 in the station
master, but is inserted in slot 3 in the station option (missing module; see example in the
next section). The online view (station master) shows an incorrect module in slot 4. In the
real configuration, the module in slot 3 indicates an error via an LED display.
Response to modules that are not present
If modules are entered as not present in the control data record, the automation system
behaves as follows:
• Modules designated as not present in the control data record do not supply diagnostics
and their status is always OK. The value status is OK.
• Direct writing access to the outputs that are not present or writing access to the process
image of outputs that are not present: Remains without effect; no access error is signaled.
• Direct reading access to the inputs that are not present or reading access to the process
image of inputs that are not present: Value "0" is supplied; no access error is signaled.
• Write data record to module that is not present: Remains without effect; no error is
signaled.
• Read data record from module that is not present: The output parameter STATUS of the
instruction RDREC supplies the value 80A3
Distributed I/O system
System Manual, 12/2023, A5E31861578-AL
Configuration control (option handling)
10.5 Behavior during operation
"General CM error".
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