WIP: 16C firmware hack for more memory

[brouhaha]

(01-22-2023 02:53 AM)brouhaha Wrote:  What doesn't work is:
[...]
3. GTO . nnn doesn't work for 204 and above
4. The display of program line numbers above 210 (not 203!) wrap around, such that 211 is 99, etc., and wrap around again each time the number hits 210.

I've just gotten those fixed.

For GTO ., the 16C firmware has a compare for >= 204. I just had to NOP that out. It still compares to the actual end of program, so I don't think the compare against 204 was actually necessary.

For line number display, the 16C firmware does the conversion from the internal program pointer to the BCD step number in three pieces, for bytes within register, unit registers, and multiples of 16 registers. The code only handled one increment of 16 registers, because there were only 29 total in a real 16C. Patching that to loop fixed it, at least as far as step 427, the last step if the RAM base address is lowered to 0xc0 instead of the standard 0xe0. I think it should be good to 999, though. As with the 15C, line 1000 will probably not be shown correctly.

If I don't patch the firmware to limit program size to 999 steps, how would people feel about steps 1000 to 1nnn being displayed as negative 000 through negative nnn? For that matter, would that be acceptable on the 15C?