BECKHOFF BK3000 - Manual (Page 11)

Basic information
BK3xxx/LC3100 11
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
Power on selftest
Bus terminal test
Structure list
PLC start /
Communication start
Stop
OK Error
The bus coupler reports the error to the master by means of the Profibus
diagnostics. Clearing the error returns the bus coupler to its normal
operating mode.