Reading from physical addresses..

[Fernando RUIZ]

On Thu, 1 May 2003 23:24:29 -0400 (EDT), Shailesh Hingole wrote:

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> From: Shailesh Hingole <shingole at cs.binghamton.edu>
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> 
> Hi there,
>  I need to read from a range of physical addresses (for
> ex. 0x000-0x1000) from an application in RTEMS. When I say that, these are
> the actual locations on the physical memory and not on the process address
> space. 
> 
> What is the best way to do it?
> 
> Is it possible to do it from an application?
> 

Hi,
  My experience is that you are free to build a C pointer in order to read/write the I/O memory
mapped space.

unsigned short char * pb = (unsigned short char *) 0x008000;

*pb=15  by example.

You can do this always like a label in your link file memory map and declare like an external
variable in your C program.

The physical memory is the real memory at least in my experience (sh HITACHI and pc386 cpus).

Drivers need to do this. I have flash memory, rtc, uarts, and more devices and always I declare a
structure and declare like external variable from C. 
I can set up the memory adress after in the link file when the linking process.

Is it right for all CPU's?

BRGDS.

> 
> thanks,
> Shailesh

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