RE: [ECOS] ARM port: how to handle ROM at address 0 without MMU ?

["Doyle, Patrick" <WPD at dtccom dot com>]

Is this on a new board that you are designing or is it on an existing board?
What ARM processor are you using?

Every existing board I've seen has some way to swap the chip selects around
so that you can make RAM show up at address zero and ROM show up at whatever
address the RAM was at.

Sometimes this is built into the device itself.

If you are designing a new board around a device that doesn't support
swaping chip selects, then you might consider adding an external (fast) CPLD
to do the swapping for you.

HTH...

--wpd


> -----Original Message-----
> From: heinricg@esiee.fr [mailto:heinricg@esiee.fr] 
> Sent: Friday, February 13, 2004 4:48 AM
> To: ecos-discuss@ecos.sourceware.org
> Subject: [ECOS] ARM port: how to handle ROM at address 0 without MMU ?
> 
> 
> Hi all,
> I'm seen this topic discussed earlier on the list but I never 
> really found an answer that matched my needs. The thing is I 
> have a platform that has:
> - ROM at address 0
> - no MMU
> 
> With the normal vectors.S file, I obviously get a data abort 
> when it tries to write into exception vectors, as these are 
> located in ROM.
> 
> The question is: what do you think is the best way of 
> modifying the vectors.S file in order to handle this? It 
> seems like I will have to have a vector table in RAM and 
> modify vectors.S so that exception handlers just jump to 
> addresses set up in the RAM-vector table. Is that it or is 
> there more to do? I'm worried that I may have to hack a lot 
> of other files in eCOS... which will certainly result in a 
> pretty unstable port as I am may not be aware of the 
> implications of what I'll do.
> 
> Thanks for your attention,
> Greg.
> 
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