Cogent 637 board

Jay Monkman jtm at
Thu Nov 10 02:48:50 UTC 2005

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.

More information about the users mailing list