Rockwell Automation 1785-CHBM ControlNet PLC-5 Hot Backup System User Manual - Manual (Page 92)

Publication 1785-UM024B-EN-P - January 2003
B-12 Backup States
Though the complete Status File is not crossloaded, there are six
words in this file that are transferred from the primary system to
the qualifying system. These six words are the real-time clock.
The Qualification Data Table crossload does not occur if the
Data Table Structures are not the same. If you want to ensure
that a Qualification Data Table crossload occurs, you must
enable equivalence checking for the Data Table structure area.
If, for some reason, the Qualification Data Table crossload fails,
qualification also fails and a major fault is declared for the
qualifying system. (Refer to Chapter 5 for descriptions of specific
major fault codes.)
• Transition to Run mode
Once the complete Data Table crossload is complete, the
qualifying PLC-5 system transitions into Run mode. Although the
PLC-5 system is now in Run mode, the PLC-5 processor is not
through with qualification and is still in the No Control backup
state. Also note that any outputs in the qualifying processor that
are not ControlNet redundant connections are now controlled
by the PLC-5 processor. This includes any local resident chassis
outputs, remote I/O channel outputs, and non-redundant I/O
connections on the ControlNet channel.
• State data table crossload
Even though a Qualification Data Table crossload has occurred,
some of the crossloaded data may have become stale. For
example, if the Qualification Data Table crossload takes 10
seconds, the data in the original data table file that was
transferred is 10 seconds old. In order to bring certain state
information in the data table up to date, a Qualification State
Data Table crossload is performed.
The Qualification State Data Table crossload reads data table
values from the primary PLC-5 system and writes these values to
the qualifying PLC-5 system. The State Data Table crossload only
crossloads specific parts of the data table. There are 4 different
parts of the data table that are crossloaded:
– Timer Accumulators
– Counter Accumulators
– PD elements
– User-selectable files