MAMEWorld Forums - Programming - MegaPlay Programming

The megatech has an extra Z80 and an extra SMS video chip that acts as an overlay, there's also a bios rom on the motherboard for this.

The MAME emulation of Megaplay actually isn't very good right now, the extra Z80 which is typically handled to program the credits etc. often ends up desyncing with the game logic, allowing you to start the game without that cpu realising, so you end up with problems like 'press start to play' flashing even after starting. A lot of the port behaviors are guessed.

I believe (but have no proof) that the extra instruction rom (read by the extra Z80) actually can be seen in the 68k map at the 3Meg mark too, which would limit the size of the games.

In terms of game code the 68k side isn't plain MD games either, because it had a bunch of extra code to communicate with the extra Z80.

As for lockouts and stuff, people would really need to test it.

Adding a new set in MAME is pretty simple, copy the ROM definition for another game in the megaplay driver, put in a new GAME macro at the bottom, and add the entry to arcade.lst, then recompile.

As I said tho, nobody has done EXTENSIVE research on the platform yet, so working with the original hardware, running test code, and creating your own document (with which MAME could be improved too) would be a wise thing to do; drivers tend to only reach 'suitable for development of games on the real system' level once somebody does that.

> Hello everybody.
> Thanks to a MAME disc I got around 2005 on my hands, I finally decided that I want to
> study computer programming and overall videogame creation, in depth.
> Oddly enough, I have two "dreams" with this: One is to create a pirate cartridge
> (XD), and the other is to be involved with an Arcade videogame in one or another way.
> Most probably it's "too late" for it (considering the gaming status nowadays) and I'm
> not gonna get any of my games exported to work in a real hardware, but if I can do
> something that works properly in the platforms I think is enough =)
>
> I have worked for a couple of years on the Sega Genesis, as a hobby. And I'm getting
> started with my final and first serious open-source project for it, Sonic Crackers
> (here's a longer thread about it:
> http://assemblergames.com/l/threads/sonic-crackers.59925/).
> As you can see I'm going with a very arcade-ish style for it. The good news are that
> the Sega Genesis have a "specialized" adaption for the Arcade world, and that is the
> Sega Megaplay. In an attempt of finding out information about this platform (of which
> there's not much), I tried to inspect a few things within the Megaplay version of
> Sonic the Hedgehog. There are three ROMs: ep15176.ic1, ep15177.ic2 and
> ep15175-01.ic3. The first two seem pretty similar to the Sega Genesis ROM, just that
> bytes are split or "crossed" (ep15176.ic1 holds what would be at address 0x000000,
> 0x000002, 0x000004, etc., and ep15177.ic2 holds what would be at address 0x000001,
> 0x000003, 0x000005, etc.). And finally there's ep15175-01.ic3, which seem to hold all
> strings the Megaplay displays, and perhaps some other misc config.
> Right now, I only know some basics of C/C++, and so far I have made very primitive
> and simple programs with it. I'm not too experimented with it, so I barely understand
> what MAME does to emulate the Megaplay. So, my question is: How does the Megaplay
> work? What considerations do I need to have with the system? Do the Megaplay have the
> TMSS lockup system just like the Sega Genesis 2 and up? How does the game know about
> MegaPlay-specific values, such as quantity of credits, or difficulty mode specified
> on the DIP Switches? Is the ROM header/structure much different than the standard of
> Sega Genesis ROMs? http://pastebin.com/4fDyHMZc (Wow, how have the tabulation messed
> up so bad? :V)
>
> Now, about MAME itself, how do I add my game to the built-in list in the source code?
> you know, specifying the ZIP's file name, the filenames within the ZIP, the driver
> required... Also, if on the future I manage to finish my game, may it be supported in
> further official versions of MAME, just like a new "bootleg" would be?
>
> And finally a less technical question: What you think are the main differences
> between an Arcade and a home-console game? It seems like 16-bit and up Arcade games
> tend to focus much more on the variety, throws more stuff on screen at once, but
> because of the extra effort required from the dev team, Arcade games tend to be a bit
> shorter. Arcade games seem to be made to be understood as soon as you start the game,
> and its gameplay seem to be more towards the player's reflexes. Is there anything
> else I should note?
>
> Thank you!