After buying a 2020 ETM that is Volvo original part, I had to reprogram it. Because the bootloader controlled the initial CAN settings during ETM powerup and self-test, in my case it was configured for 125kbps bus for a 2.9 S80. Turns out the ETM's memory 29F200BB was configured in x8 mode, which means deleting bootloader block 0x2000 also deleted 0x0-0x3FFF, I was left with no initial PC, stack pointer and VBR table. But not knowing this, I only wrote 0x2000-0x3FFF so the bootloader was in fact there.
With the boot loader bricked and my tenacity, I had to try and BDM into the ETM which to my knowledge only one other person has. Most people did not know what the MCU was for sure but was an MC683XX, I had to search block diagrams of several processors and compare to the exposed die structures, which yielded an MC68376. From there I had to find Pin 1, with careful needle probing I managed to find all BDM pins
From there I had to create a fixture. Using a prototype PCB board with through-holes, a lot of hot glue, and needles glued to pens acting as probes, many, many many iterations of taking it all apart because the needles would move, I created this monstrosity ( I know its ugly but you have to cut me some slack).
From here I managed to get BDM access using T5Luke's BDM reader. It had to be patched to allow me to also write. In this case I opted to use the BDM's CALL command and manually call the bootloader which worked! From there I spammed the CAN bus with FF86 command and managed to upload the SBL again. The SBL was specially patched to allow 2 things to happen:
1) Allow deletion and reprogramming of 0x0 block
2) Never quit/exit on erroneous CAN command or any error.
These were redundancies. A second redundancy was created in the form of a backup PBL at address 0x16000 specially patched to allow it work from there(tested) so that if bootloader is entirely deleted, there is a second copy to BDM into.
With this safeties in place, I have fully managed to revive my ETM.
