LEDs 
 
CP 343-1 
Manual, 12/2018, C79000−G8976−C201-08 
33 
 
Note 
When the "MAINT" LED lights up, important error messages and/or diagnostics interrupts 
have occurred. The CP continues in RUN mode.
 
Check the entries in the diagnostics buffer of the device.
 
LEDs for displaying the CP communications status 
In addition to the LEDs that signal the CP state, the following LEDs provide information 
about the status of the CP interface to Industrial Ethernet. 
Table 4- 2  LEDs: RX/TX, X1P1, X1P2 
RX/TX (green) 
 
The CP is sending/receiving over Industrial Ethernet. 
Note: 
PROFINET IO services are not signaled here. 
X1P1 / X1P2 
(green / yellow) 
Port has no connection to Industrial Ethernet. 
 
Existing connection via port to Industrial Ethernet (LINK 
 
LED flashes yellow (constant light green): 
Port sending / receiving over Industrial Ethernet or 
PROFINET IO. 
Note: 
All received / sent frames are signaled for each specific port 
including those simply forwarded by the switch. 
 
There is permanent data transfer at the port via Industrial 
Ethernet (e.g. PROFINET IO). 
Module identification (PROFINET interface) 
 
Note 
Module identification - make the port LEDs flash briefly 
With the help of Web diagnostics or the online functions of STEP 7, you can search for and 
identify the module in the rack. The options for this are as follows:
 
  In Web diagnostics 
You click the "Flash" button in the update center. 
  In STEP 7 
You click the "Flash" button in the "Browse network" dialog 
If you click the "Identify" or "Flash" buttons, all the port LEDs of the PROFINET interface 
flash briefly.