Rockwell Automation 1785-CHBM ControlNet PLC-5 Hot Backup System User Manual - Manual (Page 91)

Publication 1785-UM024B-EN-P - January 2003
Backup States B-11
PLC, we recommend that you disable equivalence checking first
to avoid the condition where a PLC-5 processor cannot become
qualified due to failing an equivalence check. Once all the edits
are tested and placed into both PLC-5 systems, you can re-
enable the equivalence check.
Word 49 in the ControlNet Backup Configuration and Status file
gives you equivalence check status for a qualified backup
system. A bit is set for each equivalence check area if the
equivalence areas checksum differs between the two processors.
This word is updated every few seconds so that you can know,
if secondary qualification were to happen, which equivalence
checks would pass, and which equivalence checks would fail.
• Complete data table crossload
If all the equivalence checks pass, a Qualification Data Table
crossload is performed. This crossload reads the data table file
values from the primary system and writes those values into the
corresponding data table files in the secondary system.
This data table crossload is performed while the qualifying
PLC-5 system is still in Program mode. It is necessary to remain
in Program mode until the data table crossload is finished in
order to prevent the qualifying system from major faulting or
going into an odd state due to uninitialized data table values. It
is safer for the qualifying PLC-5 system to first do the Data Table
crossload and then to go into Run mode. In that case, the data
table values are close to the values on the currently executing
primary system.
– Status File
– ControlNet Backup Configuration and Status File
– ControlNet Data Input File (DIF)
– ControlNet Data Output File (DOF)
– ControlNet Configuration File
– ControlNet I/O Status File
– ControlNet Diagnostic File
IMPORTANT
The time it takes to do the Qualification Data Table
crossload primarily depends on the amount of data
table data to be crossloaded. All elements of all data
table files are crossloaded in the Qualification Data
Table crossload, with the exception of the following
files. These files cannot be crossloaded because they
contain processor-specific configuration and status
information.