AVR-Chat

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/