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how to get memory slot not zeroed

I see options for target

default start      size   Noinit
        0x20000000 0x200
V       0x20000200 0xffff   v

and still a variable @ 0x20001348 zeroes out on reset/run

Erik

what then is the meaning of the noinit checkbox? the variable zeroes out on startup

Erik

Parents

0 Andrew Queisser over 13 years ago in reply to erik malund

Hi Erik,

The program below, compiled with "use micro-lib", uVision 4.22.22:

#include <stdio.h>
#include <stdint.h>
#include "stm32f10x.h"

int32_t NoInit____zero_init __attribute__( ( section( "NoInit"),zero_init) ) ;
int32_t NoInit __attribute__( ( section( "NoInit")) ) ;
int32_t simpleGlobal;

int main(void)
{
        printf("NoInit-zero_init is %d at %x\n", NoInit____zero_init, (int)&NoInit____zero_init);
        printf("NoInit is %d at %x\n", NoInit, (int)&NoInit);
        printf("simpleGlobal is %d at %x\n", simpleGlobal, (int)&simpleGlobal);

        return 1;
}

prints out:

NoInit-zero_init is 103643149 at 20000004
NoInit is 0 at 20000000
simpleGlobal is 0 at 20000200

using this scatter-load:

LR_IROM1 0x08000000 0x00100000  {    ; load region size_region
  ER_IROM1 0x08000000 0x00100000  {  ; load address = execution address
   *.o (RESET, +First)
   *(InRoot$$Sections)
   .ANY (+RO)
  }
  RW_IRAM1 0x20000000 UNINIT 0x00000200  { ;no init section
        *(NoInit)
   }
  RW_IRAM2 0x20000200 0x00018000  {  ; RW data
   .ANY (+RW +ZI)
  }
}

If you single step in the assembly view before you hit main you'll see that the scatterloader adds code to initialize the NoInit variable but not the NoInit____zero_init variable.

Andrew

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