I too have been trying to do this to debrick a GTab 3. I found a Russian website where the guys have manage to do it. Its a little tricky to understand the translation. There is a bit of a question mark around something to do with 'removing a resistor around read/write time.' I have been wondering if you need to boot the Tab so that the processor configures the eMMC, and then remove a resistor (with the board powered once the chip has initialised?!) that allows the clock of the SD to take over. I was planning to look at the eMMC data sheet next to see if I can confirm if this is the case. Why I can't post a link for the first 10 posts on here is beyond me, but if you Google 'AP_PS_HOLD (TP)' its the 7th link in the results. Perhaps someone with more than 10 posts could find it and post it for the benefit of others! Even better, if someone who's tech savvy and fluent in Russian takes a look, perhaps an explanation in English on here would be a big help
---------- Post added at 01:18 PM ---------- Previous post was at 12:45 PM ----------
I have connected DAT0, CLK, CMD and GND between the eMMC and SD card using a microSD-to-SD adapter. I have applied 2.8V to VDD and VDDF, current consumption settles at 300mA which the Russian site states is an indication that the eMMC has entered read/write mode. I can see the clock ok on the scope. CMD and DAT0 remain high though, no signal is detected. The eMMC does not appear as a drive in disk utility. I have not tried Flashnul yet as the Russian site suggests.