Diode help... HELP!

At 07:15 PM 2/22/00 -0500, Bill wrote: <circuit deleted> Your circuit is nearly equivalent. I'm guessing that you don't have the pins pulled high to Vcc through a small enough resistor. This is what I think is happening. When the input pins are floating, there is enough leakage to pull them high, but when they are grounded directly they go low. The back side of a diode "looks" like an open circuit to the floating pin. You can test my theory as follows. Connect pin 1 to a diode then to ground through a switch. Read back the pin while changing the switch. What do you get? (given your previous experience it will probably read as a logic '1' both ways) Now pull the pin high by connecting a 4.7K resistor between the pin and Vcc behind the diode so you have this: Vcc | R (4.7K) | Pin ----+-----|>|----/ ---Ground Now repeat the experiment. If I'm right you'll see the switch this time. If I'm wrong you should look for some Shottky diodes :-) --Chuck