STM32U385, CubeMX generated SystemClock_Config does not enable HSE Clock if it is only used in the MSI PLL mode

[CecilW]

Environment

• STM32CubeMX 6.18.1, MCU database DB.6.0.181
• STM32Cube FW_U3 V1.4.0
• MCU: STM32U385CGT6

Steps to reproduce

1. System Core → RCC → High Speed Clock (HSE) = Crystal/Ceramic Resonator (type does not matter)
2. System Core → RCC → Parameter Settings → RCC Parameters → MSIS/MSIK Auto Calibration = MSIS auto calibration
3. Clock Configuration: HSE input frequency = 16 MHz, and set the MSIS auto-calibration source mux to HSE
4. Don't use HSE for anything else (SYSCLK, ADC/DAC, RTC, MCO, ICLK, SAI1)
5. Generate code
    

In SystemClock_Config() the init struct is missing the field to enable the HSE (RCC_OscInitStruct.HSEState = RCC_HSE_ON;).
It is only generated if HSE is used by any other peripheral (e.g. the ADC clock).

Attached is a minimal .ioc file to reproduce it. By selecting anything but HSE in the ADC/DAC clock mux in the clock configuration HSE is no longer getting enabled in SystemClock_Config().

 

Best Regards,
Cecil

[Andrew Neil]

It seems reasonable that, if nothing uses the HSE, then it is not enabled?

 

[CecilW]

MSIS/MSIK Auto Calibration mode can either use the LSE or HSE(16 or 32 MHz). If this feature is enabled, the HSE should be enabled aswell if i understand it correctly.