Hey guys,
I've been thinking about Cinematronics sound off and on for a while
now since we will need to do something about it in the emulator. It's
true that most of the sounds are triggered by single output bits, but
there are some major exceptions. Most games use a shift register to
effectively increase the number of outputs which is simple enough but
not all the sounds can simply be digitized. Oh, BTW don't use 4066s
just use TTL multiplexors to get the right bits to the right places.
I suppose an overview of sound hardware would help, so let me grab my
manuals here.....
Space Wars:
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I seem to recall there are 5 on-off type outputs to control sounds. Even
if there is wave shaping you can still digitize them and use the output
as a trigger to start playing samples.
Star Castle:
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Uses a shift register for extra outputs which mostly behave like Space
Wars. There is an exception though: 3 of the outputs go into a 3-bit
D/A converter. The analog output controls a VCO (voltage controlled
Oscillator) who's output is converted to TTL. The problem is that there
is an RC circuit with a long (10sec) time constant between the D/A and
the VCO. This can not be simulated by triggering digitized sounds. The
voltage could be rising (between levels) and suddenly they tell it to
go back down! This sound is an important part of the game IMHO.
RipOff:
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Similar to Star Castle. Includes another RC circuit controlling a VCO
with some other goofy stuff after that. Again you can't just sample the
sound because there is no starting point. Also the pitch can be changing
at different rates for any given pitch. i.e. letting it settle to level 2
and the changing to level 3 causes a slow change through 2.5 while going
from 2 to 6 would cause a fast sweep through 2.5. This really can't
be done with samples. I don't know what type of hardware those williams
sound boards have, maybe they can emulate this type of thing. Kurt???
Solar Quest:
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This one adds another type of sound. Some of the outputs (8 I think) are
used as a divisor for a high frequency clock. This allows tones to be
generated by dividing by different values. Not hard, they even use all
digital ICs for it, but it is yet another different type of sound generation.
Tail Gunner:
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This has a silly anomaly. Here's how the Joystick works: The DAC in the
MONITOR used for X-position also has it's output run to 2 separate
comparators. The comparator outputs go to a 2-to-1 multiplexor that is
controlled by one of the regular outputs normally used to control sound.
The output of the comparator goes to one of the normal inputs on the
motherboard. ACK! They use this configuration to do successive approximation
under software control. It's actually a nice hack to read an analog joystick
but it adds another "feature" to a universal sound board.
So there you have it, 4 different things:
1) regular sounds that can be sampled
2) DAC-RC circuit-VCO type sounds
3) divider type tones
4) strange signal routing for Tail Gunner
And then theres the other games..... The mystery game has a really different
configuration from what I've heard from Steve.
I've gone on long enough. Hey put me on the Williams list, I have a Joust
board set laying around :-)
-- ___ __ _ _ _ | \ / \ | | | || | Engineer/Programmer | _/| || || |_| || |__ " What makes someone care so much? |_| |_||_| \___/ |____) for things another man can just ignore. " -S.H.
