memory value change after click reset chip

[hjuns]

Hello,

I use CubeIDE 1.3.0, STM32F769II.

When i debug variable value.

I found value having strange value.

It always happen when i click "reset chip".

Memory address is 0x20012C0.

when i start debug. It have 0 value.

But when i click "reset chip". 0x20012C0 memory value is changed.

How can i fix it.

Please help me.

Thanks.

[TDK]

Some variables get initialized during boot. This address could be within one of them. Why do you think it's a problem or that it should be 0?

[waclawek.jan]

Place a data breakpoint on that address, or single-step from the reset vector.

JW

[Tesla DeLorean]

Review .MAP file, check stack settings.

Walk the Reset_Handler code.

Could also be debugger related.

[hjuns]

This address is .data sector, not .bss.

It is initialized global address sector.

So it should be set 0.

[hjuns]

You are right.

I set break point this address.

Reset_Handler change value sometimes.

But i allocate 0x20012C0 address into .data sector (Initialized global variable) not .bss .

finally 0x20012C0 address value should be set to 0.

Because it initialized global variable.

Reset_Handler:  
  ldr   sp, =_estack      /* set stack pointer */
 
/* Copy the data segment initializers from flash to SRAM */  
  movs  r1, #0
  b  LoopCopyDataInit
 
CopyDataInit:
  ldr  r3, =_sidata
  ldr  r3, [r3, r1]
  str  r3, [r0, r1]
  adds  r1, r1, #4
    
LoopCopyDataInit:
  ldr  r0, =_sdata
  ldr  r3, =_edata
  adds  r2, r0, r1
  cmp  r2, r3
  bcc  CopyDataInit
  ldr  r2, =_sbss
  b  LoopFillZerobss
/* Zero fill the bss segment. */  
FillZerobss:
  movs  r3, #0
  str   r3, [r2]
  adds  r2, r2, #4
    
LoopFillZerobss:
  ldr  r3, = _ebss
  cmp  r2, r3
  bcc  FillZerobss

Reset_Handler set 0 in CopyDataInit function.

LoopFillzerobss function change 0x20012C0 address value.

How can i do that. :sad_but_relieved_face:

[TDK]

Usually you just define variables and let the linker sort out where to put them. That way there is a clear separation between .data and .bss. The default startup script relies on this to be the case.

> But i allocate 0x20012C0 address into .data sector (Initialized global variable) not .bss .

How did you do this? What does your linker file look like?

[hjuns]

Thank you for your answer.

I define large size variable.

"Para" variable allocated 0x200004b4 ~ 0x20002014.