Re: [ECOS] Platform Memory Layout

[Andrew Lunn <andrew dot lunn at ascom dot ch>]

On Wed, Jun 11, 2003 at 10:19:47AM +0000, Michael Anburaj wrote:
> Hi,
> 
> I am working on a port for an ARM920T & took aaed2000 under /hall/arm/arm9 
> as the sample. I considered the ROMRAM configuration for redboot. The 
> following is from the mlt_arm_arm9_aaed2000.ldi:
> 
> MEMORY
> {
>    ram : ORIGIN = 0, LENGTH = 0x1F40000
>    lcd : ORIGIN = 0x1f60000, LENGTH = 0xa0000
> }
> 
> SECTIONS
> {
>    SECTIONS_BEGIN
>    SECTION_fixed_vectors (ram, 0x20, LMA_EQ_VMA)
>    SECTION_rom_vectors (ram, 0x8000, LMA_EQ_VMA)
> 
> 
> Questions:
> 1. Can anyone tell me or lead me to a document about the regions (for ARM), 
> fixed_vector & rom_vector?
 
See 2 for fixed vectors. The rom_vectors are the virtual
vectors. These are described in the porting guide.

> 2. If fixed_vectors is the ARM's exception vectors, then this should be at 
> 0x0000.0000. But, here I see that it's  laid at 0x20 instead. Am I missing 
> something?

Yes. The exception vectors at location 0-0x1f contain instructions to
load the pc with the values in 0x20-0x3f. Its done like this because
you cannot jump to any 32bit address with only a 32bit opcode. You
need somewhere else to store the actual address to jump to. This is
the fixed vectors.
 
> 3. I don't find the memory configuration window in the configtool (linux).

Thats because if does not exist. You need to use version 1 on Win32,
or just edit the files directly.

   Andrew
        

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