AVR-Chat

Perhaps the original poster is confusing 1=output 0=input for DDR

On Wed, 31 Aug 2005 11:35:08 -0700
Dave Hylands <dhylands@gmail.com> wrote:

> Hi Thomas,
> 
> On 8/31/05, Thomas Keller <tkeller1@neb.rr.com> wrote:
> > On Wed, 2005-08-31 at 10:36 -0700, Dave Hylands wrote:
> > > >   Perhaps I am missing something, here.  AVR processors have
> > > selectable
> > > > pull UP resisotrs on each and every digital I/O pin.  Since a low
> > > > voltage is a logic 1, you don't need "pull down" resistors on AVR
> > > > inputs.
> > > Ummm - a low voltage (0v) is a logic zero. A high voltage (5v) is a
> > > logic one.
> > 
> >    Not according to AVR data sheets, it's not.
> 
> And where exactly are you referring to?
> 
> Page 239 of tha ATmega8 data sheet (Electrical Characteristics) says
> that the output low voltage for Ports A, B, C, and D is at most 0.7v
> for a 5v device and that the output high voltage is at least 4.2v.
> 
> The table on page 51 that shows the functionality of the PORT pins
> shows that a 1 written into a PORT pin is Output High (assuming DDR is
> set for output) and 0 is Output Low.
> 
> -- 
> Dave Hylands
> Vancouver, BC, Canada
> http://www.DaveHylands.com/
> 
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