Re: Cinematronics multigame?

> > Now I remember what I was thinking for switching games. Since a
> > multigame
> > will need a daughter card for ROMs, I figured a game-select latch
> > could
> > sit on the same card with the following things happening:
> >
> > 1) power-up resets it to game 0 - the menu
> > 2) one address line causes a second register to load i.e. if A12 goes
> > high,
> > the value in A0-A3 gets loaded into this second latch.
> > 3) when the person "selects" a game, the menu program stops reseting
> > the
> > watchdog - causeing a "soft" reset which also loads the second
> > register
> > into the game-select register.
> >
> Is A12 basically unused in all games? (I wonder since Boxing Bugs has a
> big EPROM daughtercard-- but I don't know much about Cinemat hardware.)

Actually I meant A11. There is nothing unused on the Cinematronics
platform. Everything is 12bits and they bank switch to get a more than
4K of ROM. The bank switch is done with a Jump instruction since there
is only one active bank at a time. RAM sits on a separate (internal) bus
and is of no use here. What I meant was there would be *2* latches. If
a game set the value in one it wouldn't matter, because it only gets
copied to the other (the real game select) by a watchdog-fired reset.
I *THINK* this is valid - i.e. no games let the watchdog go under normal
circumstances.

> For the Sega Multigame I just mapped a new I/O address and hang the bank
> select latches off of that. Even if you don't have the ability to
> memory map stuff directly, you can still use the address-line only
> scheme, but it might be wise to use a GAL and have a little state
> machine that handles the latch. (So something like address bus=
> %101010101010 followed by %01010101xxxx results in xxxx being latched.
> The odds of getting &AAA followed by &55x in "real" code seems pretty
> small.)

Good idea, but I think the odds of getting a watchdog reset from game
code fairly low. OTOH, if the GAL could switch games when the program
jumps back to zero it would save the trouble of running the reset line...

> Another thing I did on the Sega Multigame which might be useful-- I was
> able to find an area of memory that was big enough for the menu system

Unused space? Across all games? And standardized text display so the menu
program can be tiny... You're dreaming ;-)

> FWIW, I have a DOS (and pretty much a Windows) based vector graphics
> editor running for making game graphics, fonts, whatever. Just a matter
> of adding an "export" routine to format the data for a particular
> hardware platform. Be happy to add a Cinemat format if you like.

I was going to roll my own tonight. I'll make the character format
available so people can modify the font later - as well as the string
table. I'm actually going to waste space to make coding simpler since
getting *anything* to work is progress at this point :-) I haven't hand
assembled stuff in years...

> I can also test your Cinemat code on real hardware now too, if you
> like...

Thanks, I'll send it when I've tested it under emulation.

-- 
 ___   __   _   _  _
|   \ /  \ | | | || |       phkahler@oakland.edu     Engineer/Programmer
|  _/| || || |_| || |__     " What makes someone care so much?
|_|  |_||_| \___/ |____)      for things another man can just ignore. " -S.H.