'Completely stupid question - more stupidity'
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?
Harold M Hallikainen
|On Sun, 10 May 1998 21:28:42 +0100 Catch-It
<FILETREK.DEMON.CO.UK> writes: Catch-It
>Does this mean that in effect there is no (or very very little)
>into the pin in input mode? If for example I stuffed that LED and
>connected between supply and the pin, then set the pin to input, I
>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!
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