Lpc2000

dsidlauskas1 wrote:
> Consider the following code:
> 
> ============================
> char buf[]={1,2,3,4,5,6,7,8};
> int *ip, x[4];
> 
> for (i=0; i<4; i++)
>     {
>     ip = (int *)&buf[i];
>     x[4]  = *ip;
>     }
> =============================
> The Keil compiler compiles this without warning, but does not produce
> the expected (for me) result in x. The problem is that Keil uses the
> LDR instruction to effect the transfer and this is valid only on 4
> byte boundaries.
> 
> GCC compiles but does give a non-aligned access warning.
> 
> I believe that the compiler has enough information to use byte aligned
> transfers, and should, or at least give a warning.
> 
> Anybody want to weigh in on this one.
> 
> Thanks in advance for your comments.
> 
> Dave Sidlauskas
> 

Hello Dave,

I'm not really sure what you expect from this piece of code, but I think your try to copy these 8
bytes in 4 half-word (16bit) operations in a loop. If yes you should increment your counter variable
i by 2 instead of 1.

I would suggest:
==================================================
char buf[]={1,2,3,4,5,6,7,8};
int *ip, x[4];		/* assuming that int is 16bit-wide on your compiler */

ip = (int*) buff;

for (i=0; i<4; i++) {
    x[i] = *ip++;		/* copy content with halfword-post-increment */
}
===================================================

-- 
/************************************************
 Do you need a tiny and efficient real time
 operating system (RTOS) with a preemtive
 multitasking for LPC2000 or AT91SAM7?

   http://nanortos.net-attack.de/

 Or some open-source tools and code for LPC2000?

   http://www.net-attack.de/

************************************************/