@sameh4, I think I got it working. I basically started looking at bootloader07.c to find out if I could hack some debug info to the minicom terminal via the uart. That's when I stumbled onto this block of code:
It looks like bootloader7 is waiting for a 'g' or 'G' to come across the uart, to bootloader7's main loop, and when it does, then bootloader7 branches to address 0x8000 where the "uart02.hex" (or other code) is presumably loaded.
So, instead of using xmodem from minicom, I used "Send Files" > "ascii" from within minicom. After selecting the "uart02.hex" file, the ascii upload dialog read this:
ASCII upload of "uart02.hex"
2.2 Kbytes transferred at 2260 CPS... Done.
READY: press any key to continue...
But, I couldn't find the "any" key
I pressed a key, then when I got back to the minicom terminal, I pressed the 'g' key and then the minicom terminal displayed this:
Having a look at "uart02.c", I can see that the "notmain" function outputs the above 3 strings. So, I'm confident that "uart02.hex" was uploaded and executed. There's a loop in "uart02.c" that reads from the uart and then writes back to it, and I haven't figured out exactly what that does, but I'm not too worried about it. I have the bootloader7 working, and I think I can move forward with learning this setup. Let me know if you need help getting this working on your setup.