BECKHOFF CX9020 - Manual (Page 42)

Error handling and diagnostics
5.3 LEDs of the power supply in E­bus mode
After switching on, the power supply immediately checks the connected Bus Terminal configuration. Error­
free start­up is signaled by the red "I/O ERR” LED being extinguished. If the “I/O ERR” LED blinks, an error
in the area of the terminals is indicated. The error code can be determined from the frequency and number of
blinks. This permits rapid rectification of the error.
Display LED Meaning
Us 24 V Power supply for the CPU module
The LED lights green if the power
supply is correct.
Up 24 V Power supply for terminal bus. The
LED lights green if the power supply
is correct.
L/A off E­bus not connected
on E­bus connected / no data traffic
flashing E­bus connected / data traffic on the
E­bus.
CX9020 42 Version 1.1