Rockwell Automation 1785-CHBM ControlNet PLC-5 Hot Backup System User Manual - Manual (Page 101)

Publication 1785-UM024B-EN-P - January 2003
Data Table Crossloading C-3
On-Demand Data Table Crossloads
It may be necessary for you to crossload data table data after the
backup system has a qualified secondary processor. For example, the
Timer Accumulators may have diverged between the primary and
secondary processor over time. Or, you may have modified some data
table values on the primary processor and would like to copy those
values into the secondary processor.
The On-Demand data table crossload only occurs when you initiate it,
and can be performed only on a qualified backup system (i.e., a
backup system in which there is both a primary and secondary
processor).
The On-Demand data table crossload transfers specific files and
subelements of files from the primary processor to the secondary
processor. There are 4 different and individually selectable operations
that can be performed as part of an On-Demand data table crossload.
Each operation transfers a different part of the data table as shown
below.
• Timer Accumulators
When Timer Accumulators are crossloaded during the
On-Demand data table crossload, only the Accumulator
subelements of the Timer structures are crossloaded.
Crossloading only the Accumulator subelements of the Timer
structures allows the secondary processor to match the
Accumulator values in the primary processor without corrupting
the control bit subelements of the Timer structures in the
secondary processor. All files of Timer file types are crossloaded
(i.e., you cannot crossload a subset of Timer file types). Also, all
file elements of each Timer file are crossloaded (i.e., you cannot
crossload a subset of file elements for a particular file).
• Counter Accumulators
When Counter Accumulators are crossloaded during the
On-Demand data table crossload, only the Accumulator
subelements of the Counter structures are crossloaded.
Crossloading only the Accumulator subelements of the Counter
structures allows the secondary processor to match the
Accumulator values in the primary processor without corrupting
the control bit subelements of the Counter structures in the
secondary processor. All files of Counter file types are
crossloaded (i.e., you cannot crossload a subset of Counter file
types). Also, all file elements of each Counter file are
crossloaded (i.e., you cannot crossload a subset of file elements
for a particular file).