is there any way to change chain topology to star topology for I/O in PM864a with TU841 & TB820 ?
our topology attached.
depend on that which cpu is primary,TB820 (chain A) or TB820 (chain B) are in service.
problem is when one TU841 crashed.then following TU841s freezed.
we want change this topology to star topology...
how can we do this?
There is PFO branching unit NDBU-95 which works as "switch" for plastic fibre optics either on ModuleBus or DrivesBus, but usually it is used with ABB drives. I am not sure if it can work with TB820.
Another option how to turn your PFO network to semi-star is installation of TB826 media converters. TB826 works in pairs in order to convert PFO to glass FO and back to PFO.
See attached layout.
I think you are wrong. For redundant CPU's you can't use TB820. In your case you should use TU841 with TB840 for single I/O ModuleBus to the modules.
Look in the manual 3BSE020923R4101:
Star configuration is possible with TB825/826 - the Kamil's answer
Still you can try also with simplex POF (optic links between TB840 units) - in this case you have a ring connection between clusters and the CPU's.
Other option could be redundant Profibus modules for the stations CI840+TU847.