Each
time the core
clock (HCLK
) changes
, this
function must be called
* to update SystemCoreClock variable value. Otherwise, any configuration
* based on this variable will be incorrect.
*
* @note
- The
system frequency computed by this
function is not the real
* frequency in the chip. It is calculated based on the predefined
* constant and the selected
clock source
: *
* - If SYSCLK source is HSI, SystemCoreClock will contain the HSI_VALUE(*)
*
* - If SYSCLK source is HSE, SystemCoreClock will contain the HSE_VALUE(**)
*
* - If SYSCLK source is PLL, SystemCoreClock will contain the HSE_VALUE(**)
* or HSI_VALUE(*) multiplied/divided by the PLL factors.
*
* (*) HSI_VALUE is a constant defined in stm32f4xx_hal_conf.h file (default value
* 16 MHz) but the real value may vary depending on the variations
* in voltage and temperature.
*
* (**) HSE_VALUE is a constant defined in stm32f4xx_hal_conf.h file (its value
* depends on the application requirements), user has to ensure that HSE_VALUE
* is same as the real frequency of the crystal used. Otherwise, this function
* may have wrong result.