[ECOS] how does processor finds redboot image ?

Mark Salter msalter@redhat.com
Thu Mar 17 18:23:00 GMT 2005


On Thu, 2005-03-17 at 06:14 -0500, Sumit Chauhan wrote:
> Hi,
> 
> thanks for your reply, I understand most of it -;)
> I didnt knew basically that by default ARM maps flash at 0x00000000 ,
> 
> anyways, but / so if my redboot is in ROM mode .. redboot_ROM.ecm was
> used, will it keep on executing from flash only ? is this remapping
> done only for ROMRAM, RAM modes I believe,as else we would have been
> able to write the flash anyways -:)

The IXP4xx has a control register bit which causes flash to appear at
0x00000000 right after a reset. Early in the boot process, RedBoot
flips this bit and continues operating from flash at 0x50000000. Most
ARM boards do something similar. Sometimes, the flash is always located
at physical address zero and the MMU is used remap flash to somewhere
else and to map RAM at zero.

ROM RedBoot always executes from ROM/flash except for small bits that
have to run from RAM in order to program the flash.

--Mark



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