Diagnostic LEDs

Display	LED	Meaning
	PWR	Power supply The power LED lights green if the device is connected to a power supply unit and the unit is switched on.
	TC	TwinCAT status LED TwinCAT is in Run mode (green) TwinCAT is in Stop mode (red) TwinCAT is in Config mode (blue) Error or crash of the PLC (yellow). Applies only to TwinCAT 3
	HDD	Read/Write storage medium (red) Indicates an access to the storage medium.
	FB1	Status LED1 for fieldbus (the function is described under the fieldbus interface)
	FB2	Status LED2 for fieldbus (the function is described under the fieldbus interface)

Further Information