800xA 5.1 FP4 Upgrade
We use PM866 and PM865HI controllers.
Voted best answer
From SV 5.1 FP4 RevD to 5.1 FP4 RevE, Control Builder M libraries have been updated, so a warm download would be necessary.
Also, ABB AC 800M Connect software has been updated from version 5.1.1-1 to 5.1.1-3. So, you will also have to perform firmware upgrade. It is less risky to upgrade the firmware offline (during plant shutdown). But if the process plant is running, you can perform Online firmware upgrade (only if you have redundant hardware). But there will be temporary stop of the application, temporary disconnection of the redundancy and freeze of the I/O update.
Before downloading the application to the controller, a Difference Report is displayed. You can study the report and decide whether to accept the difference report or not.
Carefully refer the Online Upgrade section from the attached manual (3BSE035980-510).