What will happen when I forget to call system clock configuration.

[SKuma.24]

Hi People,

I need to know what will happen when I forget to set the clock configuration by using system clock configuration function. 

Is there any default clock configuration will set in the microcontroller when I forget to set clock configuration?

I'm raising this because I can able to feed the complied code which doesn't have a clock configuration. And still I can able to debug the uploaded code with stm32h7.

[AScha.3]

i am just guessing:  might be, what CubeMx shows, when you start a project (and set nothing)

HSI driving core and bus...otherwise no start code/your code could start ever.

[STTwo-32 · Accepted solution]

Hello @SKuma.24 

As you Can see in the RM0433 part 8.5.6 : "After a system reset, the HSI is selected as system clock and all PLLs are switched OFF". When you forget to call system clock configurations, a default system clock configuration is applied use the registers default parametres. You Can find more details in the reference manual of your MCU.

Best Regards.

STTwo-32

[Tesla DeLorean]

MCU just continues clocking from HSI or MSI clock that it start with by default, and all the AHB / APB are basically at DIV1 settings.

On H7 most will be running at 64 MHz HSI across all buses.

[Tesla DeLorean]

You know, you can bring up a UART and print this stuff out

void SystemDiagnostic(void)
{
  printf("\n\nCore=%d, %d MHz\n", SystemCoreClock, SystemCoreClock / 1000000);
  CORECheck();
  IDCODECheck();
  FPUCheck();
  printf("APB1=%d\n", HAL_RCC_GetPCLK1Freq());
  printf("APB2=%d\n", HAL_RCC_GetPCLK2Freq());
}