Siemens SIMATIC ET 200pro Operating Instructions Manual page 119

Interrupts, diagnostics, error messages and system events
11.1 Status and error display of the CPU
Status display 24 V DC
The 24 V DC LED lights up green when you have connected the load voltage supply 2L+. If
the LED does not light up, check whether the power supply is switched on and the fuse is
okay.
In the case of the 24 V DC LED, the CPU does not perform an "LED flash test". This means
that the LED does not light up immediately when the load voltage supply 2L+ is switched on.
Identification of the PROFINET device in the control cabinet
During initial commissioning, you must assign a device name to PROFINET IO devices. You
can have the LINK LED of a PROFINET IO device flash in STEP 7. This enables you to
clearly identify a PROFINET IO device to be addressed from several identical devices, for
example in a control cabinet.
MAINTENANCE LED
This LED indicates that a maintenance demand exists, e.g. loss of synchronization of station,
118
CPU 1516pro-2 PN (6ES7516-2PN00-0AB0)
Operating Instructions, 11/2019, A5E35873416-AC