Re: Sega xy help

>BTW, How's those Sega XY Multigames going out there??? I've heard of two
>different people that have implemented it two different ways already.

Mine is currently a single daughtercard that connects to the Z-80 socket on
the CPU board. You need to install a "jumper" board in the socket where
the security chip normally goes, and you replace the memory-mapper PROM.

At that point you can get rid of the EPROM board entirely.

Game selection works just fine by dip switches, but the "real" version is
planned as a software menu-system. I have a "sneaky" memory mapper circuit
made up out of a couple of PALs that allows selection of 4K-48K "chunks" of
memory to be enabled. (So 1 64K EPROM can hold a 48K game, plus an 8K
game, plus two 4K games for example. Mainly of interest if anyone wants
write some new games for the G-80.)

The PALs are kind-of a pain for me to develop right now (since I'm using
GALs and the only programmer for those is at work), so I might just make an
"easy" version that just bank selects 64K blocks. (And I'll pretend I
don't notice all the wasted EPROM space. Must... Resist... ;-)

I moved a Pentium machine with a PROMice on it out to the garage and have a
G-80 setup to develop software now, (that's how I did the Astro Blaster
hacks) so I'm kinda out of excuses for not getting back on it. :-) I do
want to give it a try with MAME on the PC though, so I don't have to code
in the garage...

I did a title-screen for the Multigame a while back and got sidetracked
making a "starfield" backdrop for it instead of implementing the
bank-selecting code... Whoops.

No great ideas (from me) for how to handle all the sound stuff. Control
mapping is done by a PIC on another little card, but I don't really know
how to connect it to the CPU board yet. A whole bunch of .156" connectors
just seems like a royal pain...

-Clay

P.S. Keep your fingers crossed for me-- we *might* be getting one of those
all-in-one prototype PCB makers here. That will REALLY speed up getting
these projects done! ;-) (You just give it a gerber file of your finished
printed circuit board and an hour or two later you get a two-layer drilled
and routed PCB out the other side.) Please, oh, please, oh, please.... ;-)

Clayton N. Cowgill Engineering Manager
_______________________________________________________________________
/\ Diamond Multimedia Systems, Inc. clay@supra.com
\/ Communications Division http://www.supra.com/
Received on Thu Oct 2 14:49:54 1997