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198
840 USE 106 00 January 2003
Updating PLC System Executives in a 984 HSBY System
Updating PLC
System
Executives
Bit 12 in the Hot Standby command register can be set to 1 to facilitate an executive
upgrade while one of the controllers in the Hot Standby system continues to operate
Even if it is possible to have this command register parameter be prepared for this
operation, it is strongly recommended not to have it set by configuration extension
and to set it only when needed. To do this, you can either use a Zoom screen on a
CHS instruction block in ladder logic or call up the Hot Standby command register
in the Reference Data Editor (RDE).
Upgrading the
PLC executives
while Hot
Standby system
is running
If you want to access the command register via a Zoom screen, make sure that a
CHS instruction has been inserted in ladder logic before the system is powered up.
While the Hot Standby system is running, connect to the Primary controller with
Concept. Go to the LL984 Editor and call up the Zoom screen when having the CHS
instruction inserted.
CAUTION
Overriding the Safety Checking Protection Hazard
Setting bit 12 to 1 overrides the safety checking protections between
the Primary and Standby controllers in your Hot Standby system. It is
important to reset the bit to 0 as soon as the executive upgrade
operation is complete.
Failure to follow this precaution can result in injury or equipment
damage.