What does "RCC_HSE_BYPASS_DIG" mean?

[Dat Tran]

Hi, I see STM32MP1 - M4 use "RCC_HSE_BYPASS_DIG", what does this mean?

 

And from stm32mpcube, does anyone know the calculation below to get 209MHz?

 

 

RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;

RCC_OscInitStruct.PLL.PLLSource = RCC_PLL12SOURCE_HSE;

RCC_OscInitStruct.PLL.PLLM = 3;

RCC_OscInitStruct.PLL.PLLN = 81;

RCC_OscInitStruct.PLL.PLLP = 1;

RCC_OscInitStruct.PLL.PLLQ = 1;

RCC_OscInitStruct.PLL.PLLR = 1;

RCC_OscInitStruct.PLL.PLLFRACV = 0x800;

RCC_OscInitStruct.PLL.PLLMODE = RCC_PLL_FRACTIONAL;

RCC_OscInitStruct.PLL.RPDFN_DIS = RCC_RPDFN_DIS_DISABLED;

RCC_OscInitStruct.PLL.TPDFN_DIS = RCC_TPDFN_DIS_DISABLED;

[PatrickF]

Hi @Dat Tran 

RCC_HSE_BYPASS_DIG is to control the 'DIGBYP' in case there is an external oscillator instead of a crystal (which is the case on our EV1 and DK1/2 boards). Note that M4 does not need to control this unless in 'Engineering boot' (i.e. without Linux).

For PLL settings, you could use CubeMX clock configurator and look at generated code.
Otherwise, you should read the RCC section in Reference Manual.

 

Regards.