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Re: Apple ][ to VGA monitor adapter board - looking for best color decoding method
ferdimh@gmx.de wrote:
On 10 Apr., 22:09, "Michael J. Mahon" <mjma...@aol.com> wrote:
That's why I proposed using a lookup table in SRAM to map the
Apple video to the display video, but there's no denying the
additional complexity. The versatility is *great* though. ;-)
Ouch! I didn't want to sandwich two 7x28cm boards!
And what happens when nothing is loaded into the SRAM?!
You see either a very boring or very interesting rendering. ;-)
But I've thought about doing that in ROM... I'd need a really fast ROM
then (30ns...)
Of course, you could always copy ROM into SRAM... ;-)
A CYC292 would be right, but I don't know where to get it.
I was thinking about using two "normal" 70ns EPROMs that are accessed
in alternating fashion, but that means: two ROMS, a latching shift
reg, two data latches-> 5 chips. But this would save 2 '74, 1 '157 and
two relays. so I might make it fit. The ROM cold be programmed to do
all modes in one place then.
I still prefer the analog decoding.
I've always liked the analog domain, myself. But a sweet digital
solution is a wonderful thing, too--like state machines and table
lookup.
Well, I think I said that. This is an expansion card to be plugged
into slot 7 of an Apple ][, ][+, or //e. The //gs is not supported
because of its completely different video subsystem. But if I have
time and a GS, I might consider designing a such a card for the GS. It
would be far more difficult to get a good picture then.
Because of the lack of time, I think I will continue next week...
I applaud your efforts! You've come further, faster than anyone
else I know of. Nice work!
-michael
NadaPong: Network game demo for Apple II computers!
Home page: http://members.aol.com/MJMahon/
"The wastebasket is our most important design
tool--and it's seriously underused."