Re: new board

[cgd at broadcom dot com]

At Wed, 28 Apr 2004 15:30:36 +0200, Stefano Martini wrote:
> When I start the run program (mipsel-elf-run --board .....) to execute
> a example program I get the following error messages:
> 
> mips-core: 1 byte read to unmapped address 0x0 at 0x800ab230
> mips-core: 4 byte read to unmapped address 0x0 at 0x0
> mips-core: 4 byte read to unmapped address 0x0 at 0x0
> mips-core: 4 byte read to unmapped address 0x0 at 0x0
> mips-core: 4 byte read to unmapped address 0x0 at 0x0
> mips-core: 4 byte read to unmapped address 0x0 at 0x0
> 
> I have no address in region 0x0. Is this a problem
> related to virtual and physical addresses?

I'd say that you're probably trying to read virtual address 0x0, yes,
and it doesn't do what you are expecting, because there's nothing at
that virtual address.


> I think "physical address" is an address generated by the
> processor to access a memory region.
> What is a virtual address?

http://computing-dictionary.thefreedictionary.com/virtual%20memory

For an understanding of the MIPS architecture's handling of virtual
memory and address translation, I'd advise looking that the
MIPS{32,64} Architecture for Programmers manuals available from
www.mips.com.

That documentation is more "reference" than tutuorial though.  If you
want more of a tutorial, I'd recommend See MIPS Run by Dominic
Sweetman.


cgd