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Using a Quantum 984 HSBY System
92
840 USE 106 00 January 2003
Standby on Logic Mismatches
Logic Program To function properly, the Primary and the Standby controller in a Hot Standby
system must be solving an identical logic program, which is updated on every scan
by a state RAM data transfer between the two controllers.
By default, the Standby controller is set to go offline if a mismatch is detected
between its user logic and that of the Primary controller. Switchover cannot occur
while the Standby controller is Offline.
The radio buttons provide you with the option to override this default. If you change
the parameter in this field from Offline to Running, the Standby controller remains
online if a logic mismatch is detected between its logic program and that of the
Primary controller.
CAUTION
Mismatch Hazard
A mismatch in the I/O map or configuration is not allowed under any
circumstances.
Failure to follow this precaution can result in injury or equipment
damage.
CAUTION
Switchover Hazard
If switchover occurs when the radio button is set to Running and there
is a logic mismatch between the two controllers, the Standby controller
will assume Primary responsibilities and will start solving a different
logic program from the previous Primary controller.
Failure to follow this precaution can result in injury or equipment
damage.