Lpc2000

--- In lpc2000@yahoogroups.com, "stefano_m_a" <stefano_mora@...> 
wrote:
>
> It's incredible, i found an error on the code i wrote (and i
> posted) and the code should be not running, but i saw it running !!
> 
> > ...
> > 	ldr   pc, _irq		/* .18 IRQ - _irq		*/
> > ...
> > 
> > _irq:
> > 	b timer0ISR
> > ...
> 
> _irq label should define an address and not an instruction ...
> I corrected the code as following:
> 
> 	ldr   pc, _irq		/* .18 IRQ - _irq		*/
> ...
>  
> _irq:
> 	.word __irq

Or just:

_irq:
  .word timer0ISR

 
> ...
> __irq:
> 	b timer0ISR
> 
> But now the running is bad.....
> 
> When the IRQ is fired the PC is pointing 0x18 or 0x4000.0018 ?????

0x18.  The ARM7 always reads the vectors at address 0x00-0x1C.  The 
Philips MEMMAP feature makes the first 64 bytes of RAM readable at 
both address 0x00 and 0x4000.0000.

Karl Olsen