C5-E EtherNetIP/USB Online Manual

LED signaling

Power LED

Normal operation

In normal operation, the green power LED L1 flashes briefly once per second.

Case of an error

If an error has occurred, the LED turns red and signals an error number.In the following figure, the error number 3 is signaled.

The following table shows the meaning of the error numbers.

Flash rate Error
1 General
2 Voltage
3 Temperature
4 Overcurrent
5 Controller
6 Watchdog-Reset
Note: For each error that occurs, a more precise error code is stored in object 1003h.

EtherNet/IP LEDs

The "Mod" and "Net" LEDs flash in the pattern depicted below after switching on the controller.

After the start-up sequence, the "Mod" and "Net" LEDs flash continuously until an EtherNet/IP connection is established. All other flash combinations are described in the following chapters.


The Mod LED indicates the one of the following states of the controller:

LED behavior Summary Prerequisite
Permanently off No voltage supply If the controller has no voltage supply, the Mod LED is permanently off.
Continuously green Device ready for operation If the controller is operating correctly, the LED is continuously green.
Flashing green Standby If the controller is not configured, the Mod LED flashes green.


The Net LED indicates the following status of the controller:

LED behavior Summary Prerequisite
Permanently off No voltage supply, no IP address The controller is switched off or has voltage supply but no IP address has been configured (interface configuration attribute of the TCP/IP interface object).
Flashing green No connection An IP address is configured but no CIP connection was established and an exclusive user connection timed out.
Continuously green Connected At least one CIP connection (any transport class) is established and an exclusive user connection did not time out.
Flashing red Connection timeout

An exclusive user connection whose target is the controller is running in a time out. The "Net LED" only switches back to continuously green if all exclusive user connections have been re-established.

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