[En-Nut-Discussion] AT91SAM7X512 - Changing app entry point

[Dave Warren]

Juan, the short answer is you can't because on power up 0x100000 is mapped 
to address 0x0 as well which is where the vectors have to be.

You can of course link any app to a different address but you have to start 
it from maybe a bootloader that starts at 0x100000. Be sure to copy the 
vectors to RAM 0x200000 and remap 0x0 to RAM if you need interrupts. Here is 
some code I use to start an app at 0x110000 in my bootloader

  /* Slow down the clock */
    PMC_MCKR = 0;
    while ((PMC_SR & 1<<PMC_SR_MCKRDY_BIT) == 0);

  /* Toggle external hardware reset pin. (and reset all periperals ) */
    RSTC_MR = RSTC_MR_KEY | (2 << RSTC_MR_ERSTL_BIT) | RSTC_MR_URSTEN;
    RSTC_CR = RSTC_CR_KEY | RSTC_CR_EXTRST | RSTC_CR_PERRST;
    while ((RSTC_SR & RSTC_SR_NRSTL) == 0);

  /* branch to app (no way back) */
    asm volatile ("ldr r0,=0x110000" "\n\t" "bx r0" "\n\t");

Note if you don't slow the clock restart may fail.

Hope this helps

Dave W

----- Original Message ----- 
From: "Jason Bourne" <jucanpo at hotmail.com>
To: "ARM Discussion" <en-nut-discussion at egnite.de>
Sent: Thursday, May 21, 2009 10:00 AM
Subject: [En-Nut-Discussion] AT91SAM7X512 - Changing app entry point



Hi,



I am using the AT91SAM7X-EX evaluation board, by default the application 
entry point is 0x100000. How can I change the application entry point to 
0x120000?



Thank you



Juan

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