AVR-Chat

At 07:36 PM 6/8/2008 -0500, David Kelly wrote:

>On Jun 8, 2008, at 7:00 PM, Cat Hotmail wrote:
>
> > I'm not sure of all that "volatile" does (I know I need it for
> > variables
> > that I use both in interrupts and out).
>
>
>Volatile informs the compiler that the object may change between the
>compiler's uses.

It's a little more than that. That's certainly much of the intent.  What it 
actually means though is that access to a volatile variable must take place 
in the order they are specified and exactly as many times as is specified. 
That's why a volatile write only variable makes sense.

As a consequence of that it gives the behaviour you describe.

It will not deal with issues like hardware caches but that's not a concern 
on AVRs anyway.

Robert

"C is known as a language that gives you enough rope to shoot yourself in
the foot."  -- David Brown in comp.arch.embedded
http://www.aeolusdevelopment.com/