Michael,

On Wed, 26 Jan 2005 06:40:39 -0600, michael brown wrote:

> > The only downside I can see is that using 1k it draws 5mA for each pin
> that's being pulled high but driven
> > low, and if you have a whole 8-bit port like this it's getting to be
> quite a drain on power, so not a Good
> > Thing for a battery-operated device.
> 
> No, actually it doesn't.  When the pin is in input mode, it is high
> impedance and consumes virtually no power (sub nA?).  :-)

Well I did say "driven low", by which I meant it was output (with logic low, obviously).  It means that the 
current drain is unpredictable - if it's value is (pulled) high it would be low current as you say, but low 
would be the 5mA I mentioned.  So an 8-bit port like this would draw the nA you mention if its value was 0xF, 
but 40mA if it was 0x0!  

I'm really just trying to say that this solution to the R-M-W problem is not one you can just use unthinkingly 
for every situation - its side effects need to be considered.

Cheers,



Howard Winter
St.Albans, England


-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist