Siemens SIMATIC S7-1500 Manual page 27

Meaning of LINK RX/TX-LED
Each port has a LINK RX/TX-LED. The table below shows the various "LED scenarios"
of ports for the CPU 1511-1 PN.
Table 4- 2
LED flashes green
LED flickers yellow
CPU 1511-1 PN (6ES7511-1AK00-0AB0)
Manual, 01/2013, A5E31264526-AA
Meaning of the LED
LINK TX/RX-LED
There is no Ethernet connection between the PROFINET interface
of the PROFINET device and the communication partner.
LED off
No data is currently being sent/received via the PROFINET interface.
There is no LINK connection.
The "LED flashing test" is performed.
There is no Ethernet connection between the PROFINET interface
of your PROFINET device and a communication partner.
LED green
Data is currently being received from a communication partner on
Ethernet via the PROFINET interface of the PROFINET device.
Interrupts, diagnostics, error, and system messages
4.1 Status and error display of the CPU
Meaning
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