SN-360 Firmware with 57k Ultraspeed and bugfixes

Original SN-360 firmware by Slawomir Nienaltowski (Atari Studio) 1992
This firmware by: Michal Szwaczko (WireLabs) 1997,1998,2006-2009
Reverse-engineered from bare metal, cracked, fixed and enhanced
Some comments or code annotations may be completely wrong, since they come from original disassembly back from the 1998-1999 when I had no idea of the real workings of 8051 and FDCs :)))

Also, this is not a complete rewrite of the original Nienaltowski's code just a reverse + hacks. Still, pity they hadn't done same in 1990's :)

Thanks to: drac030, seban, trub

Drive Memory map:

0x0000-0x0003 - 2797 Registers (status/command, track, sector, data)
0x8000-0x80FF - internal drive buffer, data from drive/sectors
0x8100-0x81FF - external buffer , anything read from atari

Fixes:

• fixed '80 tracks in PERCOM' bug, for 360k 5.25 drives
• fixed '0xFF byte formatting' bug for DD/DSDD
• some code cleanups, optimizations, and code-flow clarifications

New features:

• support for US DOUBLER compatible ultra speed (57kbaud,$08)
• ultraspeed sector skew, and FORMAT_CUSTOM command for SDX

TODO:

• support for 3.5 720k drives in both 9/512 and 18/256 track formats
• make format_custom really set up sector skew, now it's just faking it :)
• format real SD (just for a laugh)
• romdisk?