> What is the differences between:
> 1.Remapping memories to processor code region and
> 2.Executing the program code built with absolute addresses without
> remapping
> I read something about executing multiple image in a microprocessor (ARM
> Cortex-M3) and i'm ambiguous about differences between executing with
> remapping image to "code space" and without remapping?
> I would be grateful if you help me to understand these two concept
> clearly
> thanks
>
I think you are going to have to try again, explaining in a lot more
detail what you are trying to do. Give information about the processor
in question, and how you hope the code will work.
Also make sure you are online and checking regularly for replies so that
you can add information as requested. This is easier if you use a
proper newsreader and newsclient, rather than a web interface like
EmbeddedRelated.
There are plenty of knowledgeable people here who will help you if they
can, but we need to know what you are asking!
(And if this is homework for a course of some sort, say so. People will
try to give you helpful hints if you are honest about it.)
Reply by Clifford Heath●December 7, 20172017-12-07
On 08/12/17 11:23, Martin Riddle wrote:
> On Fri, 8 Dec 2017 08:32:19 +1100, Clifford Heath <no.spam@please.net>
>> It sounds like you are asking about Harvard architecture machines.
> Some DSP's can run code from data memory, I guess it's dependant upon
> processor type.
In which case they aren't (strict) Harvard architectures,
as I pointed out.
The AVR is like that; special instructions support data reads
on instruction space, which is annoyingly poorly handled by
compilers for accessing constant data tables.
Reply by Martin Riddle●December 7, 20172017-12-07
On Fri, 8 Dec 2017 08:32:19 +1100, Clifford Heath <no.spam@please.net>
wrote:
>On 08/12/17 02:42, mohsenzandie wrote:
>> What is the differences between:
>> 1.Remapping memories to processor code region and
>> 2.Executing the program code built with absolute addresses without
>> remapping
>> I read something about executing multiple image in a microprocessor (ARM
>> Cortex-M3) and i'm ambiguous about differences between executing with
>> remapping image to "code space" and without remapping?
>> I would be grateful if you help me to understand these two concept
>> clearly
>
>It sounds like you are asking about Harvard architecture machines.
>These have program memory, and data memory. Instructions are fetched
>from program memory, never from data memory. Data cannot be fetched
>from or written to program memory (except using special features).
>
>That means to be able to load and execute a program, there must be
>some special way to store data into program memory before executing
>it.
Some DSP's can run code from data memory, I guess it's dependant upon
processor type.
Cheers
Reply by Dimiter_Popoff●December 7, 20172017-12-07
On 07.12.2017 г. 19:59, John Speth wrote:
> On 12/7/2017 7:42 AM, mohsenzandie wrote:
>> What is the differences between:
>> 1.Remapping memories to processor code region and
>> 2.Executing the program code built with absolute addresses without
>> remapping
>> I read something about executing multiple image in a microprocessor (ARM
>> Cortex-M3) and i'm ambiguous about differences between executing with
>> remapping image to "code space" and without remapping?
>> I would be grateful if you help me to understand these two concept
>> clearly
>
> It sounds like you're asking about how relocatable code works.
> Relocatable code is code that has little to no absolute memory
> references. That means it can (in theory) run successfully at any start
> address and references memory objects loaded at user defined addresses.
>
> I'm no expert about relocatable code technology. Google will probably
> give you a sufficient number of matches if you give it "how does
> relocatable code work". I believe many modern tool sets can build
> relocatable code as an option.
>
> JJS
Not so sure this is what he is asking but in my vocabulary this is
called "position independent code", that's how it was called back in
my 6809 days :-). Means exactly the same thing of course.
Last 20+ years I have been writing essentially position independent
code (which is also reentrant), under dps this is "normal".
One can run fixed address code and is allowed to write non-reentrant
code as well but I don't know it these features work, never tried
them out... :).
The OP seems to ask just about pages (4k on ARM?) being mapped as
executable or not, I am not familiar with the ARM MMU so this is
better explained by someone else.
Dimiter
======================================================
Dimiter Popoff, TGI http://www.tgi-sci.com
======================================================
http://www.flickr.com/photos/didi_tgi/
Reply by Clifford Heath●December 7, 20172017-12-07
On 08/12/17 02:42, mohsenzandie wrote:
> What is the differences between:
> 1.Remapping memories to processor code region and
> 2.Executing the program code built with absolute addresses without
> remapping
> I read something about executing multiple image in a microprocessor (ARM
> Cortex-M3) and i'm ambiguous about differences between executing with
> remapping image to "code space" and without remapping?
> I would be grateful if you help me to understand these two concept
> clearly
It sounds like you are asking about Harvard architecture machines.
These have program memory, and data memory. Instructions are fetched
from program memory, never from data memory. Data cannot be fetched
from or written to program memory (except using special features).
That means to be able to load and execute a program, there must be
some special way to store data into program memory before executing
it.
Reply by John Speth●December 7, 20172017-12-07
On 12/7/2017 7:42 AM, mohsenzandie wrote:
> What is the differences between:
> 1.Remapping memories to processor code region and
> 2.Executing the program code built with absolute addresses without
> remapping
> I read something about executing multiple image in a microprocessor (ARM
> Cortex-M3) and i'm ambiguous about differences between executing with
> remapping image to "code space" and without remapping?
> I would be grateful if you help me to understand these two concept
> clearly
It sounds like you're asking about how relocatable code works.
Relocatable code is code that has little to no absolute memory
references. That means it can (in theory) run successfully at any start
address and references memory objects loaded at user defined addresses.
I'm no expert about relocatable code technology. Google will probably
give you a sufficient number of matches if you give it "how does
relocatable code work". I believe many modern tool sets can build
relocatable code as an option.
JJS
Reply by mohsenzandie●December 7, 20172017-12-07
What is the differences between:
1.Remapping memories to processor code region and
2.Executing the program code built with absolute addresses without
remapping
I read something about executing multiple image in a microprocessor (ARM
Cortex-M3) and i'm ambiguous about differences between executing with
remapping image to "code space" and without remapping?
I would be grateful if you help me to understand these two concept
clearly
thanks
---------------------------------------
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