----- Original Message ----- From: "Howard Winter" To: "Microcontroller discussion list - Public." Sent: Wednesday, January 26, 2005 6:55 AM Subject: Re: [PIC:] high-frequency pin toggling and the read-modify-writefeature > 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 Doh! You're right, sorry. > 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. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist