Post by thread:Completely stupid question

Thanks for the replies so far, but also I forgot one other question... >>What is the pin doing in input mode? Is it high impedance or something? Is >>there any electrical difference between the pin being in input mode or the >>pin being in ouput mode with a '0' in the SFR? >> > >actual output state. So, a pin in input mode "looks" electrically like a >capacitor of about 10pF or so. [this is bad one...] Does this mean that in effect there is no (or very very little) current flow into the pin in input mode? If for example I stuffed that LED and resistor connected between supply and the pin, then set the pin to input, I take it the LED would not light? Kind Regards Catchy...

Catch-It <spam_OUTPICLISTTakeThisOuTMITVMA.MIT.EDU> wrote: > If for example I stuffed that LED and resistor connected between > supply and the pin, then set the pin to input, I take it the LED > would not light? Correct. -Andy === Andrew Warren - .....fastfwdKILLspam@spam@ix.netcom.com === Fast Forward Engineering - Vista, California === http://www.geocities.com/SiliconValley/2499 (personal) === http://www.netcom.com/~fastfwd (business)

On Sun, 10 May 1998 21:28:42 +0100 Catch-It <Catch-ItKILLspamFILETREK.DEMON.CO.UK> writes: >Does this mean that in effect there is no (or very very little) >current flow >into the pin in input mode? If for example I stuffed that LED and >resistor >connected between supply and the pin, then set the pin to input, I >take it >the LED would not light? > True... the LED would not light. Reminds me of something I did this week. I've got some I/O pins driving address inputs on an analog demux. I took one of those address lines and connected it thru a 10K to 12VAC (power transformer secondary before rectifier). On reset, the pin is put in input mode (with the analog demuxes disabled) and the input line frequency is determined. Once that's determined, the pin is changed back to output mode to drive the demux address line. There's quite often a fair amount of stuff that only needs to be determined on reset (switch settings, line frequency, etc.). These can be "applied weakly" to the I/O pin, read, then overpowered by switching the pin to output. Saved me a pin! Harold _____________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com Or call Juno at (800) 654-JUNO [654-5866]