byuu says:
Changelog:
- MS: added ms/bus
- Z80: implemented JP/JR/CP/DI/IM/IN instructions
- MD/VDP: added window layer emulation
- MD/controller/gamepad: fixed d2,d3 bits (Altered Beast requires
this)
The Z80 is definitely a lot nastier than the LR35902. There's a lot of
table duplication with HL→IX→IY; and two of them nest two levels deep
(eg FD CB xx xx), so the design may change as I implement more.
byuu says:
Changelog:
- new md/bus/ module for bus reads/writes
- abstracts byte/word accesses wherever possible (everything but
RAM; forces all but I/O to word, I/O to byte)
- holds the system RAM since that's technically not part of the
CPU anyway
- added md/controller and md/system/peripherals
- added emulation of gamepads
- added stub PSG audio output (silent) to cap the framerate at 60fps
with audio sync enabled
- fixed VSRAM reads for plane vertical scrolling (two bugs here: add
instead of sub; interlave plane A/B)
- mask nametable read offsets (can't exceed 8192-byte nametables
apparently)
- emulated VRAM/VSRAM/CRAM reads from VDP data port
- fixed sprite width/height size calculations
- added partial emulation of 40-tile per scanline limitation (enough
to fix Sonic's title screen)
- fixed off-by-one sprite range testing
- fixed sprite tile indexing
- Vblank happens at Y=224 with overscan disabled
- unsure what happens when you toggle it between Y=224 and Y=240
... probably bad things
- fixed reading of address register for ADDA, CMPA, SUBA
- fixed sign extension for MOVEA effect address reads
- updated MOVEM to increment the read addresses (but not writeback)
for (aN) mode
With all of that out of the way, we finally have Sonic the Hedgehog
(fully?) playable. I played to stage 1-2 and through the special stage,
at least. EDIT: yeah, we probably need HIRQs for Labyrinth Zone.
Not much else works, of course. Most games hang waiting on the Z80, and
those that don't (like Altered Beast) are still royally screwed. Tons of
features still missing; including all of the Z80/PSG/YM2612.
A note on the perihperals this time around: the Mega Drive EXT port is
basically identical to the regular controller ports. So unlike with the
Famicom and Super Famicom, I'm inheriting the exension port from the
controller class.
Tim Allen