RCC_FLAG_IWDGRST Always 0

[SudoObey]

Hello,

I am working on adding an IWDG to firmware on a STM32F070CBT6TR. The Watchdog resets perfectly fine. I cause the watchdog to reset the MCU by not resetting the timer. I then try to read the RCC_FLAG_IWDGRST and it is always 0. This is what my main looks like before trying to read the flag.

bool g_wd_caused_reset = false;
int main(void)
{
  // MCU Configuration----------------------------------------------------------
  NVIC_SetVectorTable();                                // Reset vecter table
  __HAL_REMAPMEMORY_SRAM();                             // Remap boot address to SRAM

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* Configure the system clock */
  SystemClock_Config();
  if (__HAL_RCC_GET_FLAG(RCC_FLAG_IWDGRST) != RESET)
  {
    g_wd_caused_reset = true;
  }
...
...
}

 My expectation is that RCC_FLAG_IWDGRST would read 1 after the watchdog causes a reset, but I never see g_wd_caused_reset == true.

My IWDG is configured to reset after ~26 seconds.

Any help is appreciated,

Thank you.

[TDK]

Try reading it immediately after main(). Try verifying the bit directly by looking at the the RCC_CSR register.

[SudoObey]

Hello TDK,

Thank you for the reply. I changed the code as follows:

bool g_wd_caused_reset = false;
int main(void)
{
  if (RCC->CSR & RCC_CSR_IWDGRSTF)
  {
    g_wd_caused_reset = true;
  }

  // MCU Configuration----------------------------------------------------------
  NVIC_SetVectorTable();                                // Reset vecter table
  __HAL_REMAPMEMORY_SRAM();                             // Remap boot address to SRAM

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* Configure the system clock */
  SystemClock_Config();

...
...
}

I am still not seeing my boolean set to true. I connected my device to STM32CubeProgrammer while my firmware was running and the register is also 0 there. 

Thank you.

[SudoObey]

I added a breakpoint at line 4 and stepped over to complete the read. This is what the registers look like after IWDG resets the MCU:

Note that LSION and LSIRDY aren't set because I am stopping before IWDG is initialized again.

[TDK]

Something may be clearing those flags. One bit at least should always be set. Can you zip up your project and attach? You can set a breakpoint at Reset_Handler to catch it when it just resets.

[waclawek.jan]

Given non-reset-default AHBENR/APBxENR (enabled DMA, TIM1, I2C1, TIM6) I bet you have some custom bootloader running before the application.

JW

[SudoObey]

You are absolutely right. I completely overlooked my bootloader. I will look into that.

Thank you!