Siemens Simatic Operating Instructions Manual page 98

Diagnostics
10.1 Status LEDs
During boot-up of the PN/CAN LINK and after connecting the power supply, the sequence is
as follows:
1. The three LEDs light up briefly for about 1 second and then go dark again.
2. None of the LEDs light up for about 4 seconds.
3. The RUN LED starts flashing.
4. When the boot-up of the PN/CAN LINK is complete and the connection to the S7
controller is established, the RUN LED lights up.
Ethernet interface
96
LINK Indicates whether there is a physical connection on the Ethernet level.
Connection exists
On
No connection exists
Off
Rx/Tx Indicates whether a package is being sent or received
PN/CAN LINK sends or receives a package
On
No package is sent or received
Off
SIMATIC PN/CAN LINK
Operating Instructions, 03/2018, A5E39895388-AB