Lpc2000

IAR does this even simpler - use the __ramfunc declarator on the
function.  It is all auto-magic.

 

In LPC, it doesn't matter - RAM and FLASH are essentially the same speed
(barring branches).  But on other ARMs, Flash may be very slow, so
copying to RAM is important for critical routines.

 

  _____  

From: lpc2000@yahoogroups.com [mailto:lpc2000@yahoogroups.com] On Behalf
Of Karl Olsen
Sent: Wednesday, January 18, 2006 2:14 AM
To: lpc2000@yahoogroups.com
Subject: [lpc2000] Re: How to get a function running in RAM
(Lpc21xx+GnuArm)?

 

--- In lpc2000@yahoogroups.com, "arkeryd" <arkeryd@y...> wrote:

> I am using uVision3 ide together with GnuArm compiler on LPC21xx.
> 
> I need to have some interrupts enabled while using the IAP
> functions, and therefore have to place some interrupt service
> routines in RAM.
> 
> I have been looking around in documents and example files, but have
> not found any solid info on this yet.
> 
> Any example, or hint of how to achieve this would be much
> appreciated!

Put it in the .data section, and the startup code should copy it from 
flash to RAM, just like initialization values for initialized data.
You'll get some assembler warnings "Warning: ignoring changed section 
attributes for .data" that I haven't found out how to silence.  It 
works for me.

void ramfunc (int i) __attribute__ ((section(".data")));
void ramfunc (int i)
{
  /* ... */
}

You cannot call such functions directly from flash functions (or call 
flash functions from RAM functions) because RAM and flash are further 
apart than a BL instruction can reach.  You can use calls through 
function pointers instead.

Karl Olsen








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