Rockwell Automation 1785-CHBM ControlNet PLC-5 Hot Backup System User Manual - Manual (Page 45)

Publication 1785-UM024B-EN-P - January 2003
Installing and Configuring Your ControlNet PLC-5 Backup System 3-19
• User Program Control for Completion of Qualification -
you can control when qualification completes by setting and
clearing word 39 in the CBI file.
For more information on how to use this feature, refer to page
5-11.
• Designated Primary - you can force the processor at the odd
node address to always be the primary PLC processor as long as
that processor is in Run mode and is qualified.
You can select the designated primary option from the
Configuration tab of the ControlNet Hot Backup screen in
RSLogix 5. Simply choose the Odd PLC Node from the
Designated Primary pull-down menu.
Note: You must make this selection for both processors, and
they must be in Program mode.
Configuring Optional Parameters in a ControlNet Hot Backup
System
In a Hot Backup system, you must keep in mind that the configuration
parameters are system parameters and not individual PLC-5
parameters.
In a qualified backup system, the configuration parameters must be
the same for both programmable controllers. The backup system
automatically copies the parameters from the primary PLC-5 to the
secondary PLC-5. This means that one or more configuration
parameters on the secondary PLC-5 may change without any direct
involvement from the user on the secondary PLC-5.
Typically, there are two times when parameters are copied from the
primary to the secondary PLC-5:
• when the would-be secondary PLC-5 is undergoing
qualification - at this time, all configuration parameters are
passed from the primary to the secondary PLC-5. So any
configuration parameters on the would-be secondary PLC-5 are
meaningless because they will be overwritten.
• when you change the configuration parameters on the primary
PLC-5 - at this time, the changed parameters are immediately
copied to the secondary PLC-5, so there is never a time when
the parameters are different on both programmable controllers