Schneider Electric 840 USE 106 0 manual Section Transfer Control

	Using a Quantum IEC Hot Standby System
7.4	Section Transfer Control
Section Transfer Control
Section Transfer
	A new function has been added with Concept 2.5 that allows the selection of
Control	section(s) that will not be transferred from the Primary controller to the Standby
Description	controller with the exception of SFC sections. SFC sections are always transferred
	every scan.
	A benefit of selecting section(s) to not be transferred is that it allows you to reduce
	the number of IEC Hot Standby registers in the configuration and thus reduce Hot
	Standby scan time. The type of sections that should be slected for non-transfers are
	those that do not have to be updated for every scan, i.e., Section that loads recipe.
	This new function should be used along with guidelines for optimizing an IEC
	application for IEC Hot Standby Operation to reduce HSBY scan time found in
	Additional Guidelines for IEC Hot Standby , p. 147.
Using Section
	The use of this feature requires initial planning of your Hot Standby project to insure
Transfer Control	that logic not requiring an update fore every scan is segregated into its own
	section(s) so that they can be selected for non-transfer. Logic elements that can be
	used in non-transfer sections are those that have no internal states (e.g., contacts,

coils, etc.). Logic elements that should not be used in non-transfer sections are those that have internal states (e.g., timers, counters, etc.) since the internal state needs to be updated on every scan.

After sections are selected for nontransfer, the number of IEC Hot Standby registers can be reduced. To insure that you have enough IEC Hot Standby registers configured, go to the Memory Prediction dialog to view Hot Standby Memory usage. See Normal Operation, p. 140. Additionally, you can perform an analyze program under the project menu item. If you do not have enough IEC Hot Standby registers, then you will receive an error message. This message will indicate the minimum number of registers needed. A safety buffer should be added to this value to configure space for future program modifications. The reduction of the IEC Hot Standby registers is a change in the configuration and requires a complete download of the project (i.e. the Hot Standby process has to be stopped). Selecting sections to be not transferred without reducing IEC Hot Standby registers has no effect on the Hot Standby scan time.

840 USE 106 00 January 2003 135