MEGA65: SD-card controller emulation should work with freezer, fdisk and "regular usage" at least

[lgblgblgb]

Freezer functionality of Mega65 is not tested to well on Xemu. it's said not even working, also IIRC ...

Task: study the requirements (sys partition, freezer.m65, ...), create a test scenario and test it. If it does not work, or problematic, try to figure out what's missing on Xemu's Mega65 emulation which prevents it from working.

One thing which is sure missing: the thumbnail, which AFAIK uses a VIC-IV feature, which is even not implemented by Xemu. Though, without it, it should work, without thumbnail shown.

[lgblgblgb]

Info: it seems freezer stuck on checking SD-controller status:

9D04  AD 80 D6  LDA $D680
9D07  29 03     AND #$03
9D09  F0 13     BEQ ...
9D0B  EE 23 BF  INC $BF23
9D0E  D0 0C     BNE ...

Unfortunately MEGA65's SD-controller is complex enough that it was even a guess-work (try&error method took for days ...) to find a solution emulated MEGA65 can "boot". If I try to adjust things again for freezer (now I remember, I already tried this long time ago ...) then MEGA65 won't even "boot" :(

[lgblgblgb]

OK, let's rename this issue of the SD-card controller's emulation. It's more about the real case, since VIC-IV or other problems here can go into their own issue ...

[lgblgblgb]

Discussion on documentation of the SD-card controller: MEGA65/mega65-user-guide#102

[lgblgblgb]

https://github.com/lgblgblgb/mega65-utils/tree/master/tests

Preliminary test program, maybe faulty, etc. But interesting that it's totally insane, if these results are right ...

For example:

• reset sequence (taken from mega65-disk) does not seem to erase error bit ... Interestingly, at one case the reset sequence could reset the error bit. Hmm ....
• busy flags are not left as set after an error, I was sure it should be a case, but it seems it's not
• it's random if a valid command (eg read sector 0) works or not, based an error'ed command was before, even if a reset is tried to be issued between them

https://github.com/lgblgblgb/mega65-utils/blob/master/tests/sd_status_test_result.txt

It's so insane, that I'm sure my test program is faulty somewhere, though!!!!!