Re: [avr-gcc-list] Newbie - should this work?

[Christoph Plattner]

Hello,

sorry, but I cannot understad this !
How should this work. As I saw in the library (ok, it is some months 
old), the PORTD is define to 0x12 (example of a 8515).

What shall the compler do, if you write

                PORTD = 0x00;

which means

                0x12 = 0x00;

What code shall there be generated ??

So this is the reason, why I cannot understand, that this code
works. Or is the io.h completely written in another way.
I cannot see a way per include files to get a

                PORTD = 0x00;

to a

                outp (0x00, 0x12);

!!!!

Christoph



Volkmar Dierkes wrote:
> Christoph,
>
> On Sun, 19 Jan 2003 18:36:25 +0100, Christoph Plattner wrote:
>
>
> > In principal, I don't think your code is correct !
> >
> > All the other answers have not dealt with that, why ???
> >
> > PORTD and DDRD are defines to registers numbers.
> >
> > I think you have to use inp() and outp() or do a memory
> > access with `* (unsigned char *) <addr> = xxx'
> >
> >
> > example (which works):
> >
> >     outp(0xff, DDRB);
> >     outp(0x00, PORTB);
>
>
> Since AFAIK 3.2 is the recommend access to I/O ports via direct 
> access as Josh has used it. That isn't the problem.
>
> Memory access wouldn't work because they are in the io area, not in 
> memory.
>
> Volkmar
> avr-gcc-list at http://avr1.org



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