Finally I'd definitely want to examine the callstack, & any of its individual frames.
For this callstack to be legible our debugger would need to:
* Track where the stackframes begin & end in its own stack
* Decompress a symbol table to consult, from the debuggee's ROM
* Disassemble the machine code being executed.
* Build a decent Text-UI.
This is a non-trivial amount of software, but it should still fit in a processor like the one I'm designing it to debug!
3/3! Tomorrow: USB HID!