Skip to main content
RMyer.1
RMyer.1
Associate III
July 20, 2021
Question

How to define a specific address location to store data

  • July 20, 2021
  • 5 replies
  • 4419 views

Hi All,

I'm using STMCubeIDE for an assembly project and I want to be able to store some variables in Flash memory at a specific address (like data tables).

I tried using a command like this but it didn't work:

#pragma location=0x08001000

DataStart:

   .word   0

   .word   0x10 

When I look at the result in IDAPro this is what has actually happened (not located at the address I'd hoped for).

.text: 0800038E DataStart     

.text: 0800038E DCD 0

.text: 08000392 DCD 0x10

Can someone please tell me how I can force the compiler to store values at a defined address.

Thanks.

This topic has been closed for replies.

5 replies

Javier1
Javier1
Principal
July 20, 2021

Oh man assembly.... i have no clue.

What if you find a working C code that does what you want and then look in the dissasembly view from the debugger?

Use the linker script?

I believe you cannot write into flash memory like it was RAM,

you need to erase the full memory page and then write it again, or programm it at flashtime along your code

hit me up in https://www.linkedin.com/in/javiermuñoz/
RMyer.1
RMyer.1Author
Associate III
July 20, 2021

I wasn't trying to write to the flash with the program running (but you are right, there is specific processes to erase and write to flash memory).

I'm just trying to set up data tables in the program so when it is compliled (and flashed using STLink) they are in specific locations when the program is written to the MCU.

Javier1
Javier1
Principal
July 20, 2021

Then yes, you need to tell the linker script hey i need you to set this variables in this specific flash positions.

Similar to what i did here under @Community member​ advice

hit me up in https://www.linkedin.com/in/javiermuñoz/
RMyer.1
RMyer.1Author
Associate III
July 20, 2021

Ok thanks I'll have a read of that later (long thread).

I was hoping it might just be a simple as an .org directive, unfortunately what this seems to do is just advance the location from current to + whatever is defined as the value after .org

Javier1
Javier1
Principal
July 20, 2021

You can read it all if you want but i was pointing to the solution : (just change ram for flash)

in the linker script:

...............................
 .fini_array :
 {
 . = ALIGN(4);
 PROVIDE_HIDDEN (__fini_array_start = .);
 KEEP (*(SORT(.fini_array.*)))
 KEEP (*(.fini_array*))
 PROVIDE_HIDDEN (__fini_array_end = .);
 . = ALIGN(4);
 } >FLASH
 
 /*javi*/
 /*https://community.st.com/s/question/0D53W00000trgpiSAA/how-to-boot-to-random-address-without-vecttaboffset-stm32f072*/
 /* redirected vector must go to top of the RAM */
 .ram_vector :
 {
 *(.ram_vector)
 } >RAM
 /*javi*/
 
 
 
 .................

in my c code

/* USER CODE BEGIN PV */
volatile uint32_t __attribute__((section(".ram_vector,\"aw\",%nobits @"))) ram_vector[VECTOR_TABLE_SIZE];
extern volatile uint32_t g_pfnVectors[VECTOR_TABLE_SIZE];
/* USER CODE END PV */

hit me up in https://www.linkedin.com/in/javiermuñoz/
Terms & ConditionsAccessibility statement