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Re: [avr-libc-dev] gcc-3.3 branch

From: E. Weddington
Subject: Re: [avr-libc-dev] gcc-3.3 branch
Date: Wed, 15 Jan 2003 10:36:29 -0700

On 15 Jan 2003 at 18:02, Joerg Wunsch wrote:

> As Marek Michalkiewicz wrote:
> > So, my opinion is that it would
> > be best to simply document the fact that 16-bit I/O register access
> > works correctly only with constant addresses (which is the common
> > case for most I/O register accesses anyway).  If you need to do a
> > 16-bit write high byte first to non-constant addresses, better don't
> > depend on GCC, but write a piece of inline asm, like this (not
> > tested):
> Well, there's already a FAQ entry documenting the use of indirect IO
> port addresses within a function call, maybe we could just add this
> information there.

I would vote for this too. Atmel documents in the data sheets that 
writing to certain 16-bit registers is a special case and tells you 
how to go about doing it. If coming up with an automatic solution in 
gcc / avrlibc is problematic, then IMO documenting it again would be 
sufficient, especially if this was pointed out in the FAQ.


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