Siemens SIMATIC S7-1500 Manual page 50

Meaning of LINK RX/TX LED
Each port has a LINK RX/TX LED. The table below shows the various "LED scenarios" of the
CPU 1518-4 PN/DP MFP ports.
Table 4- 2 Meaning of the LEDs
LINK TX/RX LED
LED off
LED flashes green
LED lit green
LED flashes
yellow/green
Note
"LED" instruction
You can read the status (e.g. "On" or "Off") of LEDs of a CPU or a module using the "LED"
instruction. Note, however, that it is not possible to read the LED status of the LINK RX/TX
LEDs on all S7-1500 CPUs.
You can find additional information on the "LED" instruction in the STEP 7 online help.
CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)
Equipment Manual, 07/2021, A5E40882737-AB
There is no Ethernet connection between the PROFINET interface of the PROFINET device and
the communication partner.
No data is currently being sent/received via the PROFINET interface.
There is no LINK connection.
The CPU is performing an "LED flash test".
There is an Ethernet connection between the PROFINET interface of your PROFINET device
and a communication partner.
Data is currently being received from or sent to a communications partner on Ethernet via
the PROFINET interface of the PROFINET device.
Interrupts, error messages, diagnostics and system alarms
4.1 Status and error display of the CPU
Meaning
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