I've just installed two PC-HDW3449H-AS-PV-S3 that were supplied with firmware version V2.840.0000000.10.R, Build Date: 2021-09-30.
Looking into the official Dahua firmware page, a new version DH_IPC-HX5XXX-Volt_MultiLang_PN_Stream3_V2.840.0000000.18.R.220629 is available. But after download, the folder contains -apart from the README.txt- three different files:

I understand that the file I've to use is the last one DH_IPC_HX5XXX..., but what are the real purpose of the small MCU and 'firmware' files ?
I've read somewhere that the MCU file is related to a specific camera chip, so it should be upgraded also. But the 'firmware.bin' ?
And finally: when multiple firmware files are provided like this case the upgrade must be done in a concrete order or doesn't matter ?
Looking into the official Dahua firmware page, a new version DH_IPC-HX5XXX-Volt_MultiLang_PN_Stream3_V2.840.0000000.18.R.220629 is available. But after download, the folder contains -apart from the README.txt- three different files:

I understand that the file I've to use is the last one DH_IPC_HX5XXX..., but what are the real purpose of the small MCU and 'firmware' files ?
I've read somewhere that the MCU file is related to a specific camera chip, so it should be upgraded also. But the 'firmware.bin' ?
And finally: when multiple firmware files are provided like this case the upgrade must be done in a concrete order or doesn't matter ?