Can you help me SerialFirmwareUpgrade version 5.0.0/1 for AC800M?
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AC800M 5.0.0/1 Corresponds to 800xA System Version 5.1 Revision B.
If you have the installation media, navigate to
DVD1\Engineering & Development\Control Builder M\FirmwareFiles\bin\
and you will find the firmware files there. Follow the instructions in content.txt to write correct firmware in a flash card and you can downgrade the controller directly.
If you do not have the media, contact ABB support personal.
I do not think firmware software is re-distributable.