BECKHOFF BK4000 - Manual (Page 9)

Basic information
BK4000 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 atta-
ched 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”. The I/O RUN LED is lightening.
Start-up behavior of the bus
coupler
After troubleshooting, the bus coupler can only be brought to the normal
operating state by switching on again or by means of a field bus reset (trig-
gered automatically by the master).