Schneider Electric 840 USE 106 0 manual Standby on Logic Mismatch, Map / Configuration Hazard

Using a Quantum IEC Hot Standby System

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.
		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.
Logic Mismatch
	Concept 2.5, and the new PLC Executives delivered with it, support the Standby on
for Concept 2.5	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.

124 840 USE 106 00 January 2003