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Redundancy
Sercos III Redundancy -- Healing a Ring Break
When a ring network is employed, Sercos III provides for automatic infrastructure redundancy. If any interconnection point in the ring ceases to function, the associated Sercos III nodes will detect a ring break and loop back the end nodes, effectively operating as two lines rather than one ring.
The operation is bumpless, as the detection & recovery time for such a break is less than 25 µsec, which is less than the minimum cycle time. Sercos III can also recover from ring breaks and
"heal" with no interruption in operation. Sercos III telegrams continue to be emitted by transmit PMAs on unconnected ports and receive PMAs on unconnected ports continue to monitor for incoming
data. Thus, when a Sercos III port recognizes that a ring has by physically re-closed, it will re-activate the counter-rotating telegrams to functionally close the rings again. This operation is also
bumpless. Next >>
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