At 9:54 PM 11/5/96, Paul Kahler wrote:
>My first reaction then
>is to skip multi-intensity and go for color :-) There are no "mono-
>intensity" games, all the others use 1 bit for intensity, but I agree
>with the idea of using a mux to select what goes into the D/A.
If you get to call multibit intensity "multi-intensity" I get to call
single-bit "mono-intensity"... ;-)
>The
>question remains if the 6-bit color is treated a 3 2-bit values or something
>like Atari did with 3-bit color and 3-bit intensity. We need to look
>into that.
Hmmmm. Good point. Anyone know for sure?
>> I'm thinking of the MAX503 (I think that's the one) for the D/A. 12 bit,
>> parallel load, +-10V output, +5 supply, and two free samples from Maxim
>> free for the asking... ;-)
>
>Neat, how do they get that range from a +5V supply?
Maxim builds a lot of charge-pump devices (like RS-232 chips that generate
+-12V from a 5V supply) so I'm pretty sure that's built into the 503...
Even if it isn't though I'm sure we've got >+-10V on the boards somewhere,
but it'd be nice to not have regulators... That and the 503 has parallel
load, full 12 bit datapath which is getting harder to find now-a-days...
>Ray and I have been talking about the differences between Cinematronics
>and Atari WRT the D/A. Atari feeds a pair of integraters with the output
>of the D/A while Cine uses it as a target position which they feed into
>a pair of RC circuits (to do a rapid move, R is switched out of the
>circuit). At that point, both systems have signals that are functionally
>the same: voltage corresponds to position. Atari then uses 4 multipliers
>to compensate for the non-linearity of the monitor, while Cinematronics
>uses some strange diode thing :-) The Boxing Bugs color interface also
>uses the multiplier chips common on Atari games.
Hmmmm... Motorola is still making the MC1495's, but I think they're only
available in SOP surface mount packages... On the other hand, they're also
free to sample if you ask nice and have an official sounding company-name.
:-)
> Short term I'd like to replicate the Cinematronics D/A circuit and
>feed the position signals into my Space Duel board before the multiply
>chips. Long term we should probably replicate the Color interface but
>with support for mono-games.
If you could refresh my memory... Did Atari use the multipliers for the
BIP control? Size was just a matter of gain in the op-amps, no?
-Clay
Clayton N. Cowgill Engineering Manager
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