Clock Configuration
Start running from void SystemInit(void) in the project startup file system_stm32f4xx.c;
Frequency Configuration
/* Configure the main PLL */
RCC->PLLCFGR = PLL_M | (PLL_N << 6) | (((PLL_P >> 1) -1) << 16) |
(RCC_PLLCFGR_PLLSRC_HSE) | (PLL_Q << 24);
Coefficient configuration
Use an external clock source and configure the external clock frequency: stm32f4xx.h
#define HSE_VALUE ((uint32_t)8000000)
System clock factor
#define PLL_M 8
#define PLL_Q 7
#define PLL_N 336
#define PLL_P 2
PLL = HSE_VALUE * N / ( M * P ) = 8MHz * 336 / ( 8 * 2 ) = 168MHz
Note the macro definition in the compiler, which is valid for the entire project.
Reference notes:
1. (if) AHB maximum clock is 168MHz, APB2 high-speed clock maximum frequency is 84MHz, and APB1 low-speed clock maximum frequency is 42MHz.
2. Different PACKs installed by the KEIL compiler will cause inconsistent Lib paths and require recompilation.
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STM32F427 25M crystal oscillator to 8M
Clock Configuration Start running from void SystemInit(void) in the project startup file system_stm32f4xx.c; Frequency Configuration /* Configure the main PLL */ RCC- PLLCFGR = PLL_M | (PLL_N 6) | (((PLL_P 1) -1) 16) | (RCC_PLLCFGR_PLLSRC_HSE) | (PLL_Q 24); Coefficient configuration Use an external clock sou
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