Siemens SIMATIC S7-1500 Function Manual page 25

Meaning of the symbols in the "Symbol" column
Table 3- 1
Symbol
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Function Manual, 01/2013, A5E03484625-01
Meaning of symbols
Symbol Meaning
color
green Component is OK
gray Deactivated PROFIBUS slaves or PROFINET devices.
black State cannot be determined
The "Status cannot be determined" is displayed during system diagnostics

for all configured I/O modules and I/O systems after restart of the CPU.
However, this status can also be displayed temporarily during operation if a

diagnostic interrupt burst occurs for all modules.
It is not possible to determine the status of modules on a subsystem that is

connected to a CP.
red Component failed or is not reachable
"Not reachable" is displayed for e.g. a module that has been removed or a

module that has been configured but does not exist.
green Maintenance required (Maintenance Required)
yellow Maintenance demanded (Maintenance Demanded)
red Error - component faulty or not available due to an incorrect type
- A module in a lower module level does not have the status "Component OK"
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3.4 Module information
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