[ECOS] Guidance on ROMRAM ldi

[Michael Bergandi]

Jürgen,

Thanks for the reply.

>> In some of the other ROMRAM ldi files I looked at, the SECTION
>> declarations use only 'ram' and not 'rom'. I'm thinking this may not
>> matter depending on the order and SECTION declaration options
>> (assuming you are only working with a single chunk off RAM). Is this
>> thinking correct?
>
> In my romram.ldi file, there is no ROM part, which is correct: a romram
> application starts with (as first instructions) to copy itself from rom to
> ram.
> You also have no actual ROM part, as the name "rom" refers to the place in
> RAM where the application will be. So this is ok.
> I don't need this because our app is loaded at the start from the RAM.

Yes, I agree. The 'rom' memory region is just an offset into the RAM.
I have seen an ldi in the tree that doesn't use a separate region as
an offset, and just specifies an absolute LMA address, then uses the
FOLLOWING macro for every section thereafter. I think I prefer this
method better.

>
>> I have also seen some discussion in the archives suggesting that using
>> LMA_EQ_VMA is not the right thing to use. Is there  a final word on
>> this? Should I use only FOLLOWING, as I have seen elsewhere?
>
> I don't know, but also would like to know ;-).

Well, I still don't know :). From what I can tell, I don't think it
matters all that much.

> We don't have a VMM in our ARM7.
> I think that if you want to use the VMM of your ARM9, you should not use
> LMA_EQ_VMA (linear equals virtual) for all parts.

As it turns out, it doesn't really matter. As I said above, if you
specify a rom memory region offset, then you need to use LMA_EQ_VMA.
Otherwise, use absolute addresses and FOLLOWING.

-- 
Michael Bergandi

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