MEGA65: $D619 PETSCII keyboard scanner recent changes (also for new ROMs)

[lgblgblgb]

Migrated to #391

Functionality for the $D619 has been implemented in #350. However there is an on-going project to allow faster typing in BASIC and in general, using the more logical choice on MEGA65: the PETSCII based hardware accelerated keyboard scanner. However for the ROMs this feature to be really usable some changes had to be done in mega65-core which made the implementation incompatible with the previous one. This is in general not a problem, since not so many (if any!) MEGA65 software existed before using this feature, however it's a kind of urgent topic now, so people can use newer ROMs soon with the emulator as well. For that though, I should emulate all the changes done in mega65-core.

Resources

• mega65-core commit: https://github.com/MEGA65/mega65-core/pull/720
• mega65-core issue on the topic: https://github.com/MEGA65/mega65-core/issues/582
• mega65-rom original request for the feature: https://github.com/MEGA65/mega65-rom-public/issues/7
• ROM is in the 7_keyscan branch: https://github.com/MEGA65/mega65-rom/tree/7_keyscan

Needed changes (in nutshell)

• Empty state reads as $FF and not $00 to avoid colliding on being able to read PETSCII value 0 [DONE]
• Changes in the translation table, to be more precise: repairs [DONE]
• MODKEY / MODKEYVIEW? What are those for real? $D611 is emulated already, is this something different?
• key auto-repeat exact policy?

Milestones

• dev branch already has the $FF as empty modification: with the new ROM, I can type, though any modkey usage will result in very strange result, which is totally OK at this point, since I miss the other needed changes

[lgblgblgb]

There were additional changes in MEGA65-core in regard of this feature.

[lgblgblgb]

Note: by ROM defaulting to use a hardware, queue based keyboard scanner, it will be relative easy to support a proper "paste text" function. With a software solution (matrix scanning by ROM) it's hard to tell, if a faked key is "consumed" yet, and we can't know when I can advance further for the next character to be faked. However, with hw queue, I can exactly know, when to emit a new character: if there is place in the queue. It also guarantees the maximum possible throughput in terms of paste text speed, without the fear to lose a keypress.

[lgblgblgb]

Migrated to #391