BECKHOFF BK2000 - Manual (Page 9)

Basic information
BK2000 9
The operating modes of the bus coupler
When it is first switched on the bus coupler carries out a self-test to check
the functions of its components and the communications of the K-bus, and
while this is going on the red I/O LED will flash. When the self-test has
been completed successfully, the bus coupler will begin to test the
attached bus terminals (the “bus terminal test”) and read in the
configuration from which it constructs an internal structure list, which is not
accessible from outside. If an error occurs the bus coupler will enter the
operating mode “STOP”. If the start-up sequence is completed without
errors the bus coupler will enter the mode “fieldbus start”.
Start-up behavior of the bus
coupler
The bus coupler can only be returned to normal operation after fault
clearance by restarting the system.