Lpc2000

Hi,

> In IAR they gave an example like this:
> 
>   mrs   r0,cpsr               /* Original PSR value  */
>   bic   r0,r0,#MODE_BITS      /* Clear the mode bits */
>   orr   r0,r0,#SVC_MODE       /* Set SVC mode bits   */
>   msr   cpsr_c,r0             /* Change the mode     */
>   ldr   sp,=SFE(SVC_STACK) & 0xFFFFFFF8  /* End of SVC_STACK */

> What is this last statement doing, and what would be the correct 
> equiv to use in GNU?

Can't  seem to find a reference to it, but I seem to recall that standard IAR syntax
is that SFE is something like :
Segment (Flash ?) End.

So, bascially ldr   sp, =SFE(SVC_STACK) & ....

loads the SP with the ABSOLUTE address of the END of SEGMENT SVC_STACK,
which is in RAM of course.

This would make sense, as you'd normally use a descending stack.
The & with 0xFFFFFFF8 is to align the stack address to an 8-byte
boundary. GNU has its own defines for that like .code x etc.

Else just ldr sp with the Start address of your (SVC Stack + The SVC Stack size).
(You'd want it to sit on top of RAM)

-- Kris


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