Redundancy switch-over in case of an SL-bus failure
- Manually reset the quiescent station
Should this case occur (both red LEDs 'ready for redundancy' on the PBK 20 are off; both PBM 90 are active), then the quiescent station must be manually reset. Whether the master or the slave is currently active can be seen from the overview (UEBERSICHT, AUSF. UEB) or from the display of the system dialog (entry top right for RED status: … ).
Should the bus traffic between the active CL and the related coordinator be interrupted (i. e. for a redundant bus: both lines are disturbed), the coordinator activates the previously quiescent station. However, the failed station remains active until bus communication has been restored so that both PBM 90 modules are active during this time. This may lead to problems, particularly if both PBM 90 modules are equipped with a master clock function.