 | | From: | thepitbullofprogramming at yahoo.com | | Subject: | what is the purpose of the memory remap regs in arm11 | | Date: | 11 Jan 2005 16:07:24 -0800 |
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Can somebody explain what is the purpose
of the memory remap registers in ARM11?
What are they used for and how are they
used? I read the reference manual section
on this and didn't get it.
The Pitbull of Programming
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| | From: | tim | | Subject: | Re: what is the purpose of the memory remap regs in arm11 | | Date: | Thu, 13 Jan 2005 01:12:59 +0100 |
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wrote in message
news:1105488444.940085.283870@z14g2000cwz.googlegroups.com...
>
> Can somebody explain what is the purpose
> of the memory remap registers in ARM11?
> What are they used for and how are they
> used? I read the reference manual section
> on this and didn't get it.
Try page 2 of this document and see if it's any better:
http://www.atmel.com/dyn/resources/prod_documents/DOC2644.PDF
This is a ARM7 derivitave but I assume that this aspect of
the ARM architecture runs through the whole range
tim
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| | From: | John Penton | | Subject: | Re: what is the purpose of the memory remap regs in arm11 | | Date: | Thu, 13 Jan 2005 13:45:23 -0000 |
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| tim wrote:
> wrote in message
> news:1105488444.940085.283870@z14g2000cwz.googlegroups.com...
> >
> > Can somebody explain what is the purpose
> > of the memory remap registers in ARM11?
> > What are they used for and how are they
> > used? I read the reference manual section
> > on this and didn't get it.
>
> Try page 2 of this document and see if it's any better:
>
> http://www.atmel.com/dyn/resources/prod_documents/DOC2644.PDF
>
> This is a ARM7 derivitave but I assume that this aspect of
> the ARM architecture runs through the whole range
Memory remapping (as described in the above link) is normally done in the
system, and is therefore not part of the ARM processor or the ARM
architecture. It is something the system designer has added in the memory
bus architecture.
The ARM11 processor itself contains a couple of "remap" registers (which I
think the OP was referring to). One allows a region of memory to be marked
as device non-shared (a private peripheral) without turning on the MMU. I
guess this is useful to allow peripherals to be used while booting the
system (before programming the page tables). The other (iirc) allows
attribute encodings from the page tables to be mapped onto different actual
attributes. This can be used to allow the attributes of large areas of
memory to be changed quickly for say, context switching, without having to
reprogram large parts of the page table.
I don't know precisely what these things are used for in real life (I'm not
a system programmer). I guess that such features are useful to some people
and some applications, but can happily be ignored by others. If you can't
think how you would use it, then don't.
John.
--
John Penton - posting as an individual unless otherwise indicated.
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