Rockwell Automation 1785-CHBM ControlNet PLC-5 Hot Backup System User Manual - Manual (Page 125)

Publication 1785-UM024B-EN-P - January 2003
Glossary
This glossary is specific to ControlNet PLC-5 Hot Backup terms
used in this manual. For a comprehensive automation glossary,
see the Industrial Automation Glossary, publication AG-7.1.
A
active switchover Refers to a condition in which the primary PLC-5 is aware of and
able to signal to the secondary PLC-5 that a switchover must
occur. This occurs when the primary goes to Program mode, or
when you supply a switchover command. This can also occur
when the designated primary becomes active, or when the
primary faults. See passive switchover.
adjusted maximum program scan
time
Applicable in synchronous mode, this is the constant time value
for the synchronized program scans of the primary and
secondary PLC-5s. This constant time value is equal to the
smallest integer number of Network Update Times (NUTs)
whose time value is equal to or greater than the maximum
program scan time you configured.
asynchronous mode A mode of operation you configure, where the program scans of
the primary and secondary PLC-5s run independently, or
asynchronously, of each other. This mode of operation is used
to optimize operating performance of the control application,
and is the default operating mode for the system.
You configure the Asynchronous mode via the RSLogix 5. You
can select this mode at any time, however, it is the setting
configured in the active primary that dictates how the system
will operate.
Note: If there is a difference in how the primary and secondary
PLC-5s are configured, the secondary PLC-5 will assume the
setting in the primary.
automatic data crossload during
qualification
A feature provided by the ControlNet PLC-5 backup system that
automatically copies data table data from the primary into the
secondary PLC-5.
When the secondary PLC-5 is switched to Run mode, it checks
whether the structure of its data table is identical to the structure
in the primary PLC-5. If so, all appropriate data from the
primary’s data table is copied into the data table of the
secondary. Files that are not crossloaded include:
• Processor Status file
• Backup Configuration and Status file