I wanted the design to use the less space possible, less construction
needed, etc.. So using 1 pic compared with 10 scrs, or 1 pic compared
with a D flip flop with a 10 input OR gate... well, i chose the pic :)
Greg

Donald Riedinger wrote:
>
> R. Martin wrote:
>
> > I didn't totaly follow the argument at the time it was of the nature
> > of a law of physics or mathemetics (or death and taxes). It was
> > calculated that the memory systems would lock up about once every
> > ten years. Nobody confirmed this experimentaly.
>
> What's wrong with 10 SCR's? 48 cents each for TO92 sensitive gate 0.8
> amp SCR's from Mouser.  20 resistors so the first switch pressed causes
> it's SCR to conduct and light it's light but pulls up the common side of
> all the bulbs (resistor from bulb common to ground) so subsequent switch
> closures will not turn on the gates of any of the other SCR's.  $5.00
> plus switches and bulbs.  Since there is no clocking of logic involved,
> it will work correctly every time plus drive healthy light bulbs.
>
> Or how about 10 D flip flops with 2 input And gates on the D input.  One
> input of each and gate goes to a switch. The not Q outputs are all or'ed
> and the output of the 10 input Or gate (actually an And gate) goes to
> all the other inputs of the And gates on the D inputs.  The Flip flops
> are clocked together at a high rate.
>
> If any switch is pressed, a high is clocked in and that flip flop Q
> output goes high lighting its light.  At the same time that flip flop's
> not Q goes low.  Now that one of inputs to the 10 input And gate
> (inverted input, inverted output Or gate) the 10 input And gate output
> will go low bringing one input of all the 2 input And gates low thus
> disabling all inputs.
>
> The first switch bounce that get clocked in is the winner.  If the #1
> contestant's switch bounces low when the clock occurs and #2's switch
> happens to be high on the next clock and #1 is low again, the machine
> makes a wrong call.  A tie would also be possible juat from propagation
> delay. Switch bounce is in milliseconds, logic can be clocked in Mhz.
> Shouldn't be a problem more than once in ten years.
>
> Same with the SCR's. SCR's wouldn't conduct and lockout other
> contestants instantaneously.  A tie would be the only failure mode with
> the SCR's.  If it's that close, maybe it is a tie.  As long as this game
> isn't a matter of life or death.  And heck, there's millionaires that
> don't pay taxes.
>
> It's at least difficult to synchronously sample inputs with a PIC.
>
> Don