Rockwell Automation 1785-CHBM ControlNet PLC-5 Hot Backup System User Manual - Manual (Page 89)

Publication 1785-UM024B-EN-P - January 2003
Backup States B-9
There are 6 different areas in which equivalence checking can
be performed:
– Program File Structure and Program Files - This checksum is
calculated for all the Program files, with the notable exception
of SFC files. This checksum continues to be calculated when
the backup system is qualified. This allows status to be
available regarding whether the Program file checksums differ
for a qualified backup system.
Note: This should only be used when the data table
structures are the same.
– Data Table Structure - This checksum is only calculated when
the PLC-5 system goes through qualification. Since the Data
Table structure cannot change when in Run mode, this
checksum does not change after qualification. The Data Table
Structure checksum includes the data table file number, the
data table file type, and the size of the data table file. The
Data Table Structure checksum does not include the data
table file privilege information or the values of the data table
file elements.
– ControlNet I/O Map Table - This checksum is only calculated
when the PLC-5 system goes through qualification. Since the
ControlNet I/O map table cannot change when the PLC-5
system is in Run mode, this checksum does not change after
qualification. The ControlNet I/O Map Table checksum only
includes the scheduled redundant connections. Thus, as long
as the scheduled redundant connections are the same
between the backup PLC-5 systems, the ControlNet I/O Map
Table checksums will match.
– ControlNet Backup Configuration and Status file - This
checksum is only calculated when the PLC-5 system goes
through qualification. Since this checksum cannot change
when the PLC-5 system is in Run mode, this checksum does
not change after qualification. The ControlNet Backup
Configuration and Status File checksum is only calculated on
the first 3 words of the ControlNet Backup Configuration and
Status File.
– Force Tables - This checksum is calculated for all I/O force
tables and for force control words, and continues to be
calculated when the backup system is qualified. This allows
status to be available regarding whether the Force Table
checksums differ for a qualified backup system. Included in
the Force Tables checksum are:
• I/O Force Table values
• Extended Force Table values
• Force Status (is forcing enabled and are forces present)