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Re: memory layout and vector location
- To: Jonathan Larmour <jlarmour at redhat dot com>
- Subject: Re: [ECOS] memory layout and vector location
- From: Cristiano Ligieri Pereira <cpereira at ics dot uci dot edu>
- Date: Mon, 13 Aug 2001 10:38:43 -0700 (PDT)
- cc: ecos-discuss at sourceware dot cygnus dot com
> > - during startup (between LED 5 and LED 4), we copy the
> > 'exception_handlers' table from '__exception_handlers' address to address
> > 0x0. But If address 0x00 is map to ROM and if we don't have MMU to make RAM
> > start at address 0x0, how could it work ?
>
> Address 0x0 is only mapped to ROM very temporarily. Once you have loaded
> and jumped to reset_vector, you are back into the address space that was
> defined in the linker, e.g. 0x4000000. The ARM does this even without an
> MMU explicitly for booting. Once you've jumped to ROM, RAM is now
> accessible at 0x0.
>
> Jifl
> --
> Red Hat, Rustat House, Clifton Road, Cambridge, UK. Tel: +44 (1223) 271062
> Maybe this world is another planet's Hell -Aldous Huxley || Opinions==mine
Jonathan,
You are saying that RAM is mapped automatically to 0x0 even without using
MMU to do that? If so, which address should be used to access ROM?
Thanks,
Cristiano.