Memory management fault on OTP reading

[Donnie]

I have ported an application to STM32H563ZI which uses the OTP area to store a key. MPU is configured. Reading the UID is possible.

void Mpu::Config(void)
{
 MPU_Attributes_InitTypeDef attr{};
 MPU_Region_InitTypeDef region{};

 /* Disable MPU before perloading and config update */
 HAL_MPU_Disable();

 /* Define cacheable memory via MPU */
 attr.Number = MPU_ATTRIBUTES_NUMBER0;
 attr.Attributes = INNER_OUTER(MPU_NOT_CACHEABLE);
 HAL_MPU_ConfigMemoryAttributes(&attr);

 /* BaseAddress-LimitAddress configuration */
 region.Enable = MPU_REGION_ENABLE;
 region.Number = MPU_REGION_NUMBER0;
 region.AttributesIndex = MPU_ATTRIBUTES_NUMBER0;
 region.BaseAddress = 0x08FFF000;
 region.LimitAddress = 0x08FFFFFF;
 region.AccessPermission = MPU_REGION_ALL_RW;
 region.DisableExec = MPU_INSTRUCTION_ACCESS_DISABLE;
 region.IsShareable = MPU_ACCESS_NOT_SHAREABLE;
 HAL_MPU_ConfigRegion(&region);

 /* Enable the MPU */
 HAL_MPU_Enable(MPU_PRIVILEGED_DEFAULT);
}

Reading the OTP area results in a memory management fault.

static void CopyKey(uint32_t* out)
{
 const volatile uint32_t * otp = reinterpret_cast<const volatile uint32_t *>(FLASH_OTP_BASE);
 for(uint16_t c = 0; c < MeterKey::LENGTH; c++) {
 out[c] = otp[c];
 }
}

See error registers:

HFSR = 00000000
CFSR = 00000082
ICSR = 0440F804
AIRCR = FA052300
SCR = 00000000
CCR = 00000201
SHCSR = 00010001
DFSR = 0000000B
MMFAR = 08FFF000
BFAR = 08FFF000
AFSR = 00000000
CPACR = 00F00000
FLASH->ECCDETR = 00000000

I have no idea why I could not read the OTP area. As you can see I get no ECC error. The first 16 bytes of block 0 are written.

Updated 24.03.2025: Added controller STM32H563ZI

[CMYL]

Hello @Donnie 

Which STM32 family you are using ?

 

Best regards

[Donnie]

Sorry.

STM32H563ZI

[CMYL]

Hello @Donnie,

I did a simple check with a very simple code as you can see below:

For your Test issue:

- May be you kept the code used for programming the OTP. Because, writing twice an OTP 16-bit word will generate ECC error (NMI).

- Another hypothesis, the debugger is reading OTP regions. Debugger will read non-programmed OTP or programmed regions twice and will cause NMI as well. In this case, avoid memory view of OTPs.

In my test:

Initially, I programmed the addresses from 0x08fff000 to 0x08fff020. 

Then, I read the programmed OTP with a simple for loop:

 

 for(flash_address= 0x08fff000; flash_address < 0x08fff020; flash_address = flash_address +4)
 {
 uint32_t c_ad;
 c_ad = *((uint32_t*) flash_address);
 printf("\n\r OTP = 0x%08x ", c_ad); 
 }

 

I'm able to read the OTP addresses as depicted below: 

best regards,

Younes