Schneider Electric 840 USE 106 0 manual Updating PLC System Executives in a 984 Hsby System

Maintenance

Updating PLC System Executives in a 984 HSBY System

Updating PLC	Bit 12 in the Hot Standby command register can be set to 1 to facilitate an executive
System	upgrade while one of the controllers in the Hot Standby system continues to operate
Executives
		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.
	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
	If you want to access the command register via a Zoom screen, make sure that a
PLC executives	CHS instruction has been inserted in ladder logic before the system is powered up.
while Hot	While the Hot Standby system is running, connect to the Primary controller with
Standby system	Concept. Go to the LL984 Editor and call up the Zoom screen when having the CHS
is running	instruction inserted.

198 840 USE 106 00 January 2003