AVR-Chat

At 07:08 PM 2/11/2005, Eric wrote:

>Here is one thing that upsets me
>
>The data direction register for port D is 0x11 (port address)  but then 
>they give 0x31 (RAM address)
>why is there a port address and ram address?
>

Because the I/O addresses also are present in ram space.
This allows you to address I/O as ram, and allows you to make some pretty 
ugly mistakes. :)
IMHO, I would prefer that this be a fuse bit setting, to turn this on or off.

On the larger devices, some of the I/O is only addressable through ram 
space, further complicating the picture.