GE Industrial Solutions Entellisys System User Manual - Manual (Page 168)

FlexLogic™ 168
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11.14.3 Failure mode
Both CPUs become inactive when one of the following conditions occurs.
1. Both CPUs have the same CPU ID. Event, “Attention Duplicate CPU IDs Found”, can be
observed in the Sequence of Events screen.
2. Tow points failure. The primary throws over to the backup but the backup cannot become
active because one of the following conditions occurs:
a. Backup physical discrete I/O card count is different than the configured discrete I/O card
count.
b. Backup is down.
c. All installed nodes are not commissioned in backup or communicating with backup.
d. None of the nodes are communicating with both CPUs.
11.14.4 Discrete I/O card redundancy
In a discrete I/O card redundancy system (both CPUs have discrete I/O cards and identical
configuration), the active CPU has discrete I/O card contact outputs actuated, and the inactive
CPU has discrete I/O card contact outputs blocked. During the throw-over or throwback
transition, both discrete I/O card contact outputs are blocked (all contact outputs stay low) for
100 to 200 milliseconds.
In a discrete I/O card non-redundancy system (only CPU A has a discrete I/O card), the system
does not actuate any contact output when the backup is active. The backup CPU (CPU B) does
not have a discrete I/O card installed.