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MaxM1
Associate II
October 7, 2026
Question

STM32CubeMX 6.17.x and higher generates MPU/FLASH configuration that causes HardFault on STM32U385RGT6Q

Hello,

while investigating a HardFault on an STM32U385RGT6Q, I noticed several differences in the code generated by newer CubeMX versions.


At the moment I am unsure whether I have overlooked a configuration dependency or whether this is an actual CubeMX code generation issue.

Environment:
MCU: STM32U385RGT6Q

Flash Configuration:

    Total Flash : 1 MB
    Bank 1      : 512 kB
    Bank 2      : 512 kB


Application Memory Layout:

    0x08000000 - 0x080FDFFF  Application Flash (1016 kB)
    0x080FE000 - 0x080FFFFF  Parameter Storage (8 kB)


Protection Settings:

    Application Area:
    Read Only by Privileged Code Only

    Parameter Storage:
    Read / Write by any Privileged level

 

In CubeMX Version 6.15.0 Flash and MPU initialisation look like this: 

static void MX_FLASH_Init(void)
{

  /* USER CODE BEGIN FLASH_Init 0 */

  /* USER CODE END FLASH_Init 0 */

  FLASH_OBProgramInitTypeDef pOBInit = {0};
  FLASH_BBAttributesTypeDef FLASH_BBSecInitStruct = {0};

  /* USER CODE BEGIN FLASH_Init 1 */

  /* USER CODE END FLASH_Init 1 */
  if (HAL_FLASH_Unlock() != HAL_OK)
  {
    Error_Handler();
  }

  /* Option Bytes settings */

  if (HAL_FLASH_OB_Unlock() != HAL_OK)
  {
    Error_Handler();
  }
  pOBInit.OptionType = OPTIONBYTE_BOOTADDR;
  pOBInit.BootAddrConfig = OB_BOOTADDR_NS0;
  pOBInit.BootAddr = 0x08000000;
  if (HAL_FLASHEx_OBProgram(&pOBInit) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_FLASH_OB_Lock() != HAL_OK)
  {
    Error_Handler();
  }

  /* Block-based page protection */

  FLASH_BBSecInitStruct.Bank = FLASH_BANK_1;
  FLASH_BBSecInitStruct.BBAttributesType = FLASH_BB_PRIV;
  FLASH_BBSecInitStruct.BBAttributes_array[0] =   0xFFFFFFFF;
  FLASH_BBSecInitStruct.BBAttributes_array[1] =   0xFFFFFFFF;
  if (HAL_FLASHEx_ConfigBBAttributes(&FLASH_BBSecInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  FLASH_BBSecInitStruct.Bank = FLASH_BANK_2;
  FLASH_BBSecInitStruct.BBAttributes_array[0] =   0xFFFFFFFF;
  FLASH_BBSecInitStruct.BBAttributes_array[1] =   0x7FFFFFFF;
  if (HAL_FLASHEx_ConfigBBAttributes(&FLASH_BBSecInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_FLASH_Lock() != HAL_OK)
  {
    Error_Handler();
  }

  /* Launch Option Bytes Loading */
  /*HAL_FLASH_OB_Launch(); */

  /* USER CODE BEGIN FLASH_Init 2 */

  /* USER CODE END FLASH_Init 2 */

}


void MPU_Config(void)
{
  MPU_Region_InitTypeDef MPU_InitStruct = {0};
  MPU_Attributes_InitTypeDef MPU_AttributesInit = {0};

  /* Disables the MPU */
  HAL_MPU_Disable();

  /** Initializes and configures the Region 0 and the memory to be protected
  */
  MPU_InitStruct.Enable = MPU_REGION_ENABLE;
  MPU_InitStruct.Number = MPU_REGION_NUMBER0;
  MPU_InitStruct.BaseAddress = 0x08000000;
  MPU_InitStruct.LimitAddress = 0x080FDFFF;
  MPU_InitStruct.AttributesIndex = MPU_ATTRIBUTES_NUMBER0;
  MPU_InitStruct.AccessPermission = MPU_REGION_PRIV_RO;
  MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_ENABLE;
  MPU_InitStruct.IsShareable = MPU_ACCESS_NOT_SHAREABLE;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);

  /** Initializes and configures the Region 1 and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER1;
  MPU_InitStruct.BaseAddress = 0x080FE000;
  MPU_InitStruct.LimitAddress = 0x080FFFFF;
  MPU_InitStruct.AccessPermission = MPU_REGION_ALL_RW;
  MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_DISABLE;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);

  /** Initializes and configures the Region 2 and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER2;
  MPU_InitStruct.BaseAddress = 0x20000000;
  MPU_InitStruct.LimitAddress = 0x2002FFFF;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);

  /** Initializes and configures the Region 3 and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER3;
  MPU_InitStruct.BaseAddress = 0x20030000;
  MPU_InitStruct.LimitAddress = 0x2003FFFF;
  MPU_InitStruct.AttributesIndex = MPU_ATTRIBUTES_NUMBER1;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);

  /** Initializes and configures the Attribute 0 and the memory to be protected
  */
  MPU_AttributesInit.Number = MPU_ATTRIBUTES_NUMBER0;
  MPU_AttributesInit.Attributes = INNER_OUTER(MPU_WRITE_THROUGH|MPU_TRANSIENT
                              |MPU_R_ALLOCATE);

  HAL_MPU_ConfigMemoryAttributes(&MPU_AttributesInit);

  /** Initializes and configures the Attribute 1 and the memory to be protected
  */
  MPU_AttributesInit.Number = MPU_ATTRIBUTES_NUMBER1;
  MPU_AttributesInit.Attributes = INNER_OUTER(MPU_NOT_CACHEABLE);

  HAL_MPU_ConfigMemoryAttributes(&MPU_AttributesInit);
  /* Enables the MPU */
  HAL_MPU_Enable(MPU_PRIVILEGED_DEFAULT);

}

 

In CubeMX Version 6.16.1 Flash and MPU initialisation looks like this:

so here Bank 2 of  the Flash initializing is missing

static void MX_FLASH_Init(void)
{

  /* USER CODE BEGIN FLASH_Init 0 */

  /* USER CODE END FLASH_Init 0 */

  FLASH_OBProgramInitTypeDef pOBInit = {0};
  FLASH_BBAttributesTypeDef FLASH_BBSecInitStruct = {0};

  /* USER CODE BEGIN FLASH_Init 1 */

  /* USER CODE END FLASH_Init 1 */
  if (HAL_FLASH_Unlock() != HAL_OK)
  {
    Error_Handler();
  }

  /* Option Bytes settings */

  if (HAL_FLASH_OB_Unlock() != HAL_OK)
  {
    Error_Handler();
  }
  pOBInit.OptionType = OPTIONBYTE_BOOTADDR;
  pOBInit.BootAddrConfig = OB_BOOTADDR_NS0;
  pOBInit.BootAddr = 0x08000000;
  if (HAL_FLASHEx_OBProgram(&pOBInit) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_FLASH_OB_Lock() != HAL_OK)
  {
    Error_Handler();
  }

  /* Block-based page protection */

  FLASH_BBSecInitStruct.Bank = FLASH_BANK_1;
  FLASH_BBSecInitStruct.BBAttributesType = FLASH_BB_PRIV;
  FLASH_BBSecInitStruct.BBAttributes_array[0] =   0xFFFFFFFF;
  FLASH_BBSecInitStruct.BBAttributes_array[1] =   0xFFFFFFFF;
  if (HAL_FLASHEx_ConfigBBAttributes(&FLASH_BBSecInitStruct) != HAL_OK)
  {
    Error_Handler();
  }

  /* Launch Option Bytes Loading */
  /*HAL_FLASH_OB_Launch(); */

  /* USER CODE BEGIN FLASH_Init 2 */

  /* USER CODE END FLASH_Init 2 */

}


void MPU_Config(void)
{
  MPU_Region_InitTypeDef MPU_InitStruct = {0};
  MPU_Attributes_InitTypeDef MPU_AttributesInit = {0};

  /* Disables the MPU */
  HAL_MPU_Disable();

  /** Initializes and configures the Region 0 and the memory to be protected
  */
  MPU_InitStruct.Enable = MPU_REGION_ENABLE;
  MPU_InitStruct.Number = MPU_REGION_NUMBER0;
  MPU_InitStruct.BaseAddress = 0x08000000;
  MPU_InitStruct.LimitAddress = 0x080FDFFF;
  MPU_InitStruct.AttributesIndex = MPU_ATTRIBUTES_NUMBER0;
  MPU_InitStruct.AccessPermission = MPU_REGION_PRIV_RO;
  MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_ENABLE;
  MPU_InitStruct.IsShareable = MPU_ACCESS_NOT_SHAREABLE;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);

  /** Initializes and configures the Region 1 and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER1;
  MPU_InitStruct.BaseAddress = 0x080FE000;
  MPU_InitStruct.LimitAddress = 0x080FFFFF;
  MPU_InitStruct.AccessPermission = MPU_REGION_ALL_RW;
  MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_DISABLE;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);

  /** Initializes and configures the Region 2 and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER2;
  MPU_InitStruct.BaseAddress = 0x20000000;
  MPU_InitStruct.LimitAddress = 0x2002FFFF;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);

  /** Initializes and configures the Region 3 and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER3;
  MPU_InitStruct.BaseAddress = 0x20030000;
  MPU_InitStruct.LimitAddress = 0x2003FFFF;
  MPU_InitStruct.AttributesIndex = MPU_ATTRIBUTES_NUMBER1;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);

  /** Initializes and configures the Attribute 0 and the memory to be protected
  */
  MPU_AttributesInit.Number = MPU_ATTRIBUTES_NUMBER0;
  MPU_AttributesInit.Attributes = INNER_OUTER(MPU_WRITE_THROUGH|MPU_TRANSIENT
                              |MPU_R_ALLOCATE);

  HAL_MPU_ConfigMemoryAttributes(&MPU_AttributesInit);

  /** Initializes and configures the Attribute 1 and the memory to be protected
  */
  MPU_AttributesInit.Number = MPU_ATTRIBUTES_NUMBER1;
  MPU_AttributesInit.Attributes = INNER_OUTER(MPU_NOT_CACHEABLE);

  HAL_MPU_ConfigMemoryAttributes(&MPU_AttributesInit);
  /* Enables the MPU */
  HAL_MPU_Enable(MPU_PRIVILEGED_DEFAULT);

}

and in version CubeMX 6.17.0 / 6.18.1

so here Bank 2 of  the Flash initializing is missing and the whole

MPU_Attributes_InitTypeDef MPU_AttributesInit = {0};

part is missing 

Only the region configuration remains.

static void MX_FLASH_Init(void)
{

  /* USER CODE BEGIN FLASH_Init 0 */

  /* USER CODE END FLASH_Init 0 */

  FLASH_OBProgramInitTypeDef pOBInit = {0};
  FLASH_BBAttributesTypeDef FLASH_BBSecInitStruct = {0};

  /* USER CODE BEGIN FLASH_Init 1 */

  /* USER CODE END FLASH_Init 1 */
  if (HAL_FLASH_Unlock() != HAL_OK)
  {
    Error_Handler();
  }

  /* Option Bytes settings */

  if (HAL_FLASH_OB_Unlock() != HAL_OK)
  {
    Error_Handler();
  }
  pOBInit.OptionType = OPTIONBYTE_BOOTADDR;
  pOBInit.BootAddrConfig = OB_BOOTADDR_NS0;
  pOBInit.BootAddr = 0x08000000;
  if (HAL_FLASHEx_OBProgram(&pOBInit) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_FLASH_OB_Lock() != HAL_OK)
  {
    Error_Handler();
  }

  /* Block-based page protection */

  FLASH_BBSecInitStruct.Bank = FLASH_BANK_1;
  FLASH_BBSecInitStruct.BBAttributesType = FLASH_BB_PRIV;
  FLASH_BBSecInitStruct.BBAttributes_array[0] =   0xFFFFFFFF;
  FLASH_BBSecInitStruct.BBAttributes_array[1] =   0xFFFFFFFF;
  if (HAL_FLASHEx_ConfigBBAttributes(&FLASH_BBSecInitStruct) != HAL_OK)
  {
    Error_Handler();
  }

  /* Launch Option Bytes Loading */
  /*HAL_FLASH_OB_Launch(); */

  /* USER CODE BEGIN FLASH_Init 2 */

  /* USER CODE END FLASH_Init 2 */

}

void MPU_Config(void)
{
  MPU_Region_InitTypeDef MPU_InitStruct = {0};


  /* Disables the MPU */
  HAL_MPU_Disable();


  /** Initializes and configures the Region 0 and the memory to be protected
  */
  MPU_InitStruct.Enable = MPU_REGION_ENABLE;
  MPU_InitStruct.Number = MPU_REGION_NUMBER0;
  MPU_InitStruct.BaseAddress = 0x08000000;
  MPU_InitStruct.LimitAddress = 0x080FDFFF;
  MPU_InitStruct.AttributesIndex = MPU_ATTRIBUTES_NUMBER0;
  MPU_InitStruct.AccessPermission = MPU_REGION_PRIV_RO;
  MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_ENABLE;
  MPU_InitStruct.IsShareable = MPU_ACCESS_NOT_SHAREABLE;


  HAL_MPU_ConfigRegion(&MPU_InitStruct);


  /** Initializes and configures the Region 1 and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER1;
  MPU_InitStruct.BaseAddress = 0x080FE000;
  MPU_InitStruct.LimitAddress = 0x080FFFFF;
  MPU_InitStruct.AccessPermission = MPU_REGION_ALL_RW;
  MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_DISABLE;


  HAL_MPU_ConfigRegion(&MPU_InitStruct);


  /** Initializes and configures the Region 2 and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER2;
  MPU_InitStruct.BaseAddress = 0x20000000;
  MPU_InitStruct.LimitAddress = 0x2002FFFF;


  HAL_MPU_ConfigRegion(&MPU_InitStruct);


  /** Initializes and configures the Region 3 and the memory to be protected
  */
  MPU_InitStruct.Number = MPU_REGION_NUMBER3;
  MPU_InitStruct.BaseAddress = 0x20030000;
  MPU_InitStruct.LimitAddress = 0x2003FFFF;
  MPU_InitStruct.AttributesIndex = MPU_ATTRIBUTES_NUMBER1;


  HAL_MPU_ConfigRegion(&MPU_InitStruct);
  /* Enables the MPU */
  HAL_MPU_Enable(MPU_PRIVILEGED_DEFAULT);


}

I am able to run my code in the Generated version of 6.15.0 and 6.16.1 but any higher cubeMX version causes a hardfault on a random RAM operation like creating lokal variables or copying memory.

The HardFault appears only after the MPU Memory Attribute configuration disappears.

If i manualy add the missing MPU memory Attribute configuration lines everything works just fine in every cubeMX version

 

In Addition to that i also would expect a different Flash initialization

The STM32U385RGT6Q contains:

128 Pages per Bank


The BB attribute configuration therefore requires:

4 x 32-bit attribute words per bank


Since my application uses:

Entire Bank 1
+
All of Bank 2 except the last two pages

I would expect something similar to:

FLASH_BBSecInitStruct.Bank = FLASH_BANK_1;
FLASH_BBSecInitStruct.BBAttributesType = FLASH_BB_PRIV;

FLASH_BBSecInitStruct.BBAttributes_array[0] = 0xFFFFFFFF;
FLASH_BBSecInitStruct.BBAttributes_array[1] = 0xFFFFFFFF;
FLASH_BBSecInitStruct.BBAttributes_array[2] = 0xFFFFFFFF;
FLASH_BBSecInitStruct.BBAttributes_array[3] = 0xFFFFFFFF;

HAL_FLASHEx_ConfigBBAttributes(&FLASH_BBSecInitStruct);

FLASH_BBSecInitStruct.Bank = FLASH_BANK_2;

FLASH_BBSecInitStruct.BBAttributes_array[0] = 0xFFFFFFFF;
FLASH_BBSecInitStruct.BBAttributes_array[1] = 0xFFFFFFFF;
FLASH_BBSecInitStruct.BBAttributes_array[2] = 0xFFFFFFFF;
FLASH_BBSecInitStruct.BBAttributes_array[3] = 0x3FFFFFFF;

HAL_FLASHEx_ConfigBBAttributes(&FLASH_BBSecInitStruct);


Only the final two pages of Bank 2 should remain writable for parameter storage.

However, recent CubeMX versions generate only the Bank 1 configuration or atleast missing have of all Pages.

 

Questions

Is the removal of HAL_MPU_ConfigMemoryAttributes() starting with CubeMX 6.17.x intentional?

If yes, where are MPU_ATTRIBUTES_NUMBER0 and MPU_ATTRIBUTES_NUMBER1 expected to be initialized?

Is the missing Bank 2 BB attribute generation a known issue?

Is CubeMX correctly handling custom Flash partitioning on STM32U385 devices?

Has anyone observed similar behaviour after migrating from CubeMX 6.15.x to newer versions?

Does this look like a CubeMX code generation regression, or is there an additional configuration step now required?

Any feedback from ST or other STM32U3 users would be greatly appreciated.

Thanks!

3 replies

Mahmoud Ben Romdhane
ST Technical Moderator
October 7, 2026

Hello ​@MaxM1 

Let me thank you for posting.

For more investigation, could you please provide the Ioc.File created with STM32CubeMX 6.15.0.

Thanks.

Mahmoud

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MaxM1Author
Associate II
October 8, 2026

Hello ​@Mahmoud Ben Romdhane 

Please find attached an example project (.ioc file) that I created using STM32CubeMX 6.15.0.

I tested the behavior again with the latest version, STM32CubeMX 6.18.1. After migrating the project from STM32CubeMX 6.15.0 to STM32CubeMX 6.18.1, the issue still persists:

  • The initialization of Flash Bank 2 is missing.
  • The generated initialization code for Flash Bank 1 also appears to be incomplete with regard to the memory layout of the STM32U385RGT6Q. However, this issue is present across all versions.
  • The MPU attributes configuration is no longer generated. Only the MPU region configuration remains.

Furthermore, the behavior appears to be independent of the MCU firmware package version being used.

The original project was created with STM32CubeMX 6.15.0 and STM32Cube_FW_U3 V1.2.1. After migrating the project to STM32CubeMX 6.18.1, the firmware package is automatically upgraded to STM32Cube_FW_U3 V1.4.0.

However, manually downgrading the firmware package back to STM32Cube_FW_U3 V1.2.1 does not change the generated code. The MPU attributes configuration and the Flash initialization code remain incomplete, and the initialization of Flash Bank 2 is still missing.

Thank you for your support.

Best regards, 

Max

Mahmoud Ben Romdhane
ST Technical Moderator
October 12, 2026

Hello ​@MaxM1 

Let me thank you for bringing these issues to our attention.

An internal tickets have been submitted to the dedicated team (Internal Ticket Numbers: CDM0066453 ; CDM0066521 ).

I will keep you informed as soon as these issues are resolved.

Thanks.

Mahmoud

 

 

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