Rockwell Automation 1785-CHBM ControlNet PLC-5 Hot Backup System User Manual - Manual (Page 23)

Publication 1785-UM024B-EN-P - January 2003
Understanding the ControlNet PLC-5 Hot Backup System Components 2-3
Compatibility Considerations
If the firmware series or revision do not match between the two
programmable controllers in a backup system, one or both
programmable controllers will detect an incompatibility and indicate a
Major Fault code 238. If the fault is cleared without correcting the
compatibility issue, the fault will continue to occur. However, the fault
will not occur in a programmable controller if it is in Run mode and is
controlling outputs.
Firmware Update Considerations
You can change the firmware in a programmable controller for two
reasons. You can either:
• upgrade an older version of firmware to a new version, or
• backflash a newer version of firmware to an older version
For example, in an operational backup system, both programmable
controller’s firmware are at Series F, Revision A. If one programmable
controller fails and needs replacing, it must be replaced with an
identical series and firmware revision (Series F/Revision A). If a spare
part programmable controller is available, but it contains Series F/
Revision C firmware, it must be backflashed to Series F/Revision A.3.
Likewise, if you want to upgrade firmware in a backup system from
Series F/Revision A to Series F/Revision C, you would perform a flash
upgrade to both programmable controllers to ensure compatibility in
the backup system.
IMPORTANT
The firmware revision in programmable controllers
in an operational backup system cannot be revised
during operation. The backup system and the
application must be powered down to revise the
firmware in one or both programmable controllers.
IMPORTANT
PLC-5 programmable controllers Series F/Revision C
contain new flash devices and do not allow
Revisions A, A.1 A.2 and B to be backflashed into
them. They can only be backflashed with Revisions
A.3 and B.1 firmware, respectively.