again, i fooled around with dualling each i/o pin as input and output.
i also ran into probs thinking about what would happen if the same
player hit their switch again, while the pin was set as output.  at
least with my couple designs i tried to come up with, i couldn't get one
that wouldn't short something out

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.
>
> Greg Brault wrote:
>
> > 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,
>
> One 22V10 PAL might just do everything for you.  My point was, a PIC
> can't look at all the inputs at once.
>
> Why do you need the decoder and encoder?  Just use port B and half of
> port A of a PIC16C54 or something.  Connect LED's through current
> limiting resistors from power to PIC I/O pins.  Connect momentary N/O
> switches to ground the I/O pins and LED cathodes when pressed.
>
> Your program sets all 10 pins as inputs then continuously scans them
> looking for a low input.  You'd probably need 100k pull-ups on the I/O
> pins.
>
> When a switch is pressed, it lights the corresponding LED through the
> switch.  The PIC sees that input is low and then jumps to a routine to
> make that input an output and then make it low until reset.
>
> Don