...you wouldn't happen to still have that JED around, would you?
Just pulled this straight off my 1200XL's U1MB:
Also, I can't thank you enough for uflash. It really puts a friendly face on a potentially frightening process; my U1MB would still be running my original ROM if it wasn't for that.
If it makes the process less intimidating and less prone to failure, then it's accomplished what I set out to do. The exercise was initially for my own benefit, since when developing the old PBI BIOS back in 2012 or so, I was updating just a small part of the ROM on real hardware several times a day and the cobbled-together, hard-coded tool I was using clearly wasn't a permanent solution. Since developing the new main BIOS and loader as well, I've been updating these sections of the ROM on four machines (five counting Incognito) countless times and the only time I had to resort to the USB programmer was when one of the old PLCC flash ROMs apparently wore out (replacing it fixed everything), or when some show-stopping Incognito bug emerged (since there's no way to test the Incognito BIOS in the emulator). The MADS target folder is mounted in RespeQt via SIO2PC and I can have the firmware on the target machine updated within a minute of assembling the code. The same folder is simultaneously mounted in Altirra and I even update the emulated U1MB using UFlash with F1 held down. There are probably more sophisticated ways of updating the emulator ROM using make tools as part of the assembly process, but since I require the firmware slot ROM for real hardware anyway, I stick with the usual procedures. I doubt I would have felt inclined to develop complete new firmware for U1MB and Incognito had this flashing tool not existed.