Adam, Thank you for your quick response! I have a couple questions... "M. Adam Davis" wrote: > 2) a Schmitt Trigger input is a nice way of saying, "this part will always turn > on and off athe the specified voltages despite process variation, etc, etc." > Thus you can put an analog signal in and it will always trigger on and off at > the same voltage levels. Other inputs will vary due to other conditions on the > chip If I had a pull down resistor, and a switch connected to Vdd, would that be enough to trigger it? Or for that matter would the opposite work? (Pullup, switch to Vss) > 3) I've not heard of a normally closed quad bilateral chip, but I bet someone > somewhere has them... When set as output portc and portd drive their lines, > either high or low, but they drive them. It doesn't have to be quad bilateral...just something normally closed :) The only thing I can think of are relays, and I was wondering if there is a solid state alternative. > 4) There are all sorts of 8, 16 and 24 bit data latches made. Look in digikey, > or other chip catalogs, you'll find what you need. It would be fairly easy to > multiplex these on a PIC, though you would need a few seperate i/o for control. > Hook the 8-bit port to the inputs of the three latches, then connect the three > enable lines to seperate i/o elsewhere (or a 3-8 or 2-4 decoder). By enabling > each in turn, you'll be extending your 8bit port to 24 bits. Will I run into problems having them all on one port? Will the microcontroller be able to drive them sufficiently all at once? > A suggestion: If you need 24 output controlled with an 8 bit port, look up the > 8255. It is an i/o chip where you can set three 8-bit ports to either input or > output. It is obsolete, but they are all over the place still. I once used the 8255 in an expansion i/o for my ZX81 :) I still marvel at that computer...it only had 4 chips for everything from video to memory to keyboard to cassette interface :) Thank you very much Adam! Josh Koffman joshy@mb.sympatico.ca