Publication 1756-UM523F-EN-P - December 2006
138 Update Modules and Redundant Systems
Update an Online
Redundant System
The redundancy system update feature of ControlLogix lets you
update the firmware in a secondary chassis while the primary chassis
is controlling outputs.
However, during a redundancy system update, remember that:
• the secondary chassis’ redundancy feature is disabled.
• the secondary chassis cannot act on a primary chassis failure.
Redundant System Definitions
IMPORTANT
Once you have updated the firmware of the modules in the
secondary chassis and downloaded the recompiled application
programs to your updated secondary chassis, you can then lock
your redundant system and switch control to the secondary
chassis without any changes to your outputs or data.
A locked switchover differs from a normal switchover in that
only you can initiate the former. A primary chassis failure
cannot initiate a locked switchover.
Attempting to update a system with busy 1756-L55Mxx
controllers will result in a loss of system control. A system that
is locked for update requires additional processor resources. A
CPU utilization of a synchronized pair of 1756-L55Mxx
controllers that exceeds 80% suggests that adequate processor
resources are not available to your application.
Term Description
Controlling Outputs When outputs are being controlled, they are active and reacting to input state changes being monitored by your
application. When not being controlled, outputs can still be active but cannot react to input state changes.
Locked for Update No application changes are allowed on either the primary or secondary controllers. Your system must enter this
state in order to initiate a locked switchover from the primary to secondary chassis.
Locked Switchover This is the process of transferring control from a locked primary chassis to a locked secondary chassis.
Locking for Update This is the process of locking a redundant system in preparation for entering the locked state.
Supports Locking This attribute in a redundancy object indicates whether a module supports the locking feature. Only secondary
chassis modules need this attribute to enable your redundancy system to enter a locked state.
Partner A partner is a module in a chassis that is in the same slot position as a module in the corresponding chassis. A
module in the primary chassis can have a partner in the secondary chassis. Likewise, a module in the secondary
chassis can have a partner in the primary chassis.
Disqualified
Secondary
The secondary chassis or modules are in either the DSwP or DSwNP states, depending on whether or not the
primary chassis or modules exist.
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