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Using a Quantum IEC Hot Standby System
124
840 USE 106 00 January 2003
Standby on Logic Mismatch
Overview To function properly, the Primary and the Standby controller in a Hot Standby
system must be solving an identical 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 program and that of the Primary controller. Switchover cannot occur
while the Standby controller is Offline.
Logic Mismatch
for Concept 2.5
Concept 2.5, and the new PLC Executives delivered with it, support the Standby on
Logic Mismatch option in the Hot Standby Configuration Extension. Logic mismatch
allows you to make online changes to the program of the Standby or Primary
controller while the HSBY system continues to run the process. The Standby on
Logic Mismatch option also allows up to date process data to be transferred from the
Primary controller after download of the modifications.
CAUTION
I/O Map / Configuration 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.