I am having an issue with my STM32F446 where I am experiencing a hardfault right after calling HAL_FLASH_Program to write data to internal flash, when I check the CFSR registerI see that the UNDEFINSTR flag is set to high.

[MOhamed_Mehery]

I am using the following code to write data to flash memory:

#include "stm32f4xx_hal.h"

#include "stm32f4xx_hal_flash.h"

#define DATA_SIZE 4

int main(void)

{

   uint32_t data[DATA_SIZE] = {0x12345678, 0x90ABCDEF, 0xDEADBEEF, 0xCAFEBABE};

   uint32_t address = 0x08000040; // Starting address of sector 0

   HAL_Init();

   HAL_FLASH_Unlock(); // Unlock flash

   // Erase sector 0

   FLASH_Erase_Sector(FLASH_SECTOR_0, FLASH_VOLTAGE_RANGE_3);

   // Write data to flash

   for (int i = 0; i < DATA_SIZE; i++) {

       if (HAL_FLASH_Program(FLASH_TYPEPROGRAM_WORD, address, data[i]) != HAL_OK) {

           // Handle write error

       }

       address += sizeof(data[i]);

   }

   HAL_FLASH_Lock(); // Lock flash

   while (1) {

       // Main loop

   }

}

Could you please help me understand why I am experiencing a hardfault and what is causing the

UNDEFINSTR

flag to be set to high in the

CFSR

register?

Thank you in advance for your help.

Best regards,

[FBL]

Hello @MOhamed_Mehery​,

Have you tried the example provided on Cube Firmware? Here is a link STM32CubeF4/Projects/STM32F446ZE-Nucleo/Examples/FLASH/FLASH_EraseProgram at master · STMicroelectronics/STM32CubeF4 (github.com)

If still facing same issue, ensure that the data you are trying to write to flash is properly formatted and aligned.

[waclawek.jan]

Which memory/address do you run this code from? You are erasing beginning of FLASH - do you remap area 0x0000'0000, and/or relocate VTOR appropriately?

JW

[Tesla DeLorean · Accepted solution]

Use FLASH that's not hosting your code.

You might need to make a hole in the F4 memory map to free a smaller block.

You need some bootable code at 0x08000000​