In normal drive mode, drive supports VSC command via TTL
In your case, I do not know
You can download demo and test this
Analog of UCommand I mean, "WD Rom Recovery tool", if I remember rightly
If WD VSC Commands are compatiable via a UART TTL adapter does that mean it's possible to select a COM port (instead of base ATA port etc) in WDMarvel and attempt to issue commands in this manner?
As for U-Command Rom recovery tool, i tried all versions with no luck, the guy who made this tool is called "Canny Feng" this is the same dude who made DRT2012 drive software - looking at the support files - i think he ripped off MRT software.... or vice versa. i think he uses a drive definition list and if it's not an exact match (with the currently connected board) the tool won't even attempt communications.
Other software which might work is the previously mentioned qtaosoft q3 drive repair tool - which is a newer uart-ttl compatiable tool, but their website is broken and i can only find the seagate version, there is a WD option but it's not usable/grayed out.
Failing that i guess i'd have figure out what ARM core & architecture the MCU is using - find specific commands relevent to this and attempt to issue these arm specific commands via terminal - or use an ARM specific tool via UART.... but this is way out of my comfort zone - and software development ain't my game.
interesting subject though - this is likely how the very expensive programs/tools (ACE, dolphin labs etc) are able to put drives into "kernel" , debug, and UART mode purely in software via the 8-pin connector at back of drive without having to touch config resistors & test points etc - they're just sending an ARM spefic command at the bootloader stage.... hence all the guff they give on not powering down the drive once in this mode. if someone had one of these expensive programs it would be relatively simple to find out what specific command is being issued.
Vlad, on a side note, when using WDR-6 (in my Semi detect "mode") rather than seeing "Disk size -1152939097061330945 - -9007336Gb" using WDMarvel, i get a different number with WDR - off the top of my head i think it displays 2001 GB and a LBA value which is pretty close to what you'd typically expect (can't remember specifically as i'm not currently on my xp machine) Also unlike WDMarvel, with WDR i am able to write a Rom file - and it claims the write was successfull.... but i don't think it actually is. i'm also able to peform ram operations etc but i haven't played around with this in WDR much.
thought this was interesting and worth mentioning, no idea if it has any relevence or not...