39 / 65Issued: 29.11.2012 Version: KR C4 Interbus 1.1 V2 en (PDF)
8 Diagnosis
8.3 LEDs on the master module
The diagnostic LEDs on the master module are all accommodated on the front 
plate. The basic functions of the module are checked when it is switched on. 
If no faults are detected, “SC” flashes green after approx. 5 seconds. “HF” 
goes out when the drivers are activated.
The state of the Interbus is indicated by other LEDs:
INST_AUTO_RESTART 0x4000 This status bit indicates that the driver should 
cyclically attempt to restart the bus in the case 
of a bus error. The bus is thus automatically 
restarted once the error has been rectified. 
INST_DOING_SHUTDOWN 0x8000 This status bit indicates that the driver is being 
shut down. This bit is only set in addition to all 
the others and serves to provide information for 
other functions (e.g. IOCTL) that must be ter-
minated. 
Designation Value Description
Fig. 8-1: LEDs on the master module
Designation Color Meaning
FC Green Reserved
SC RDY/RUN Green Interbus Ready
The controller board has the state READY or 
ACTIVE 
SC RDY/RUN Flash-
ing
Interbus Running
The controller board has the state RUN
HF Yellow Host Failure
System fault of the host
FAIL Red Failure
A fault has occurred in the Interbus system