Cogent 637 board

Lars Munch lars at
Thu Nov 10 20:55:02 UTC 2005


To me this looks very much like errata 11 in AT91RM9200 datasheet

Lars Munch

On Wed, Nov 09, 2005 at 08:48:50PM -0600, Jay Monkman wrote:
> Joel Sherrill <joel at> wrote:
> > Camilo Alejandro Arboleda wrote:
> > 
> >> I'm using RTEMS Network driver is loaded, but it seems to
> >> fail in the ISR.
> I looked tried it out, and I also got the data abort. The output you see isn't
> very helpful, but it indicates a data abort.
> It's happening in the network code. The CPU is trying to read a misaligned word.
> It looks like incoming network packets end up with the IP header starting at a
> misaligned address (because the ethernet head is aligned). When the network code
> tries to access fields in the IP header, we get a data abort.
> What I don't understand is why this didn't occur in 4.6. Maybe something changed
> in the network code. Or we just got lucky.
> I think the fix for this is to modify the network driver so the IP header is
> aligned. This will cause the ethernet header to be misaligned, but that should
> be OK.
> I'll try to come up with a fix in the next few days.
> As a workaround, you could try using 4.6.
> Thanks for pointing out this problem.

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