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/**
******************************************************************************
* @file system_stm32f4xx.c
* @author MCD Application Team
* @brief CMSIS Cortex-M4 Device Peripheral Access Layer System Source File.
*
* This file provides two functions and one global variable to be called from
* user application:
* - SystemInit(): This function is called at startup just after reset and
* before branch to main program. This call is made inside
* the "startup_stm32f4xx.s" file.
*
* - SystemCoreClock variable: Contains the core clock (HCLK), it can be used
* by the user application to setup the SysTick
* timer or configure other parameters.
*
* - SystemCoreClockUpdate(): Updates the variable SystemCoreClock and must
* be called whenever the core clock is changed
* during program execution.
*
*
******************************************************************************
* @attention
*
* Copyright (c) 2017 STMicroelectronics.
* All rights reserved.
*
* This software is licensed under terms that can be found in the LICENSE file
* in the root directory of this software component.
* If no LICENSE file comes with this software, it is provided AS-IS.
*
******************************************************************************
*/
/** @addtogroup CMSIS
* @{
*/
/** @addtogroup stm32f4xx_system
* @{
*/
/** @addtogroup STM32F4xx_System_Private_Includes
* @{
*/
#include "stm32f4xx.h"
#if !defined (HSE_VALUE)
#define HSE_VALUE ((uint32_t)8000000) /*!< Default value of the External oscillator in Hz */
#endif /* HSE_VALUE */
#if !defined (HSI_VALUE)
#define HSI_VALUE ((uint32_t)16000000) /*!< Value of the Internal oscillator in Hz*/
#endif /* HSI_VALUE */
/**
* @}
*/
/** @addtogroup STM32F4xx_System_Private_TypesDefinitions
* @{
*/
/**
* @}
*/
/** @addtogroup STM32F4xx_System_Private_Defines
* @{
*/
/************************* Miscellaneous Configuration ************************/
/*!< Uncomment the following line if you need to relocate your vector Table in
Internal SRAM. */
/* #define VECT_TAB_SRAM */
#define VECT_TAB_OFFSET 0x00 /*!< Vector Table base offset field.
This value must be a multiple of 0x200. */
/******************************************************************************/
/**
* @}
*/
/** @addtogroup STM32F4xx_System_Private_Macros
* @{
*/
/**
* @}
*/
/** @addtogroup STM32F4xx_System_Private_Variables
* @{
*/
/* This variable is updated in three ways:
1) by calling CMSIS function SystemCoreClockUpdate()
2) by calling HAL API function HAL_RCC_GetHCLKFreq()
3) each time HAL_RCC_ClockConfig() is called to configure the system clock frequency
Note: If you use this function to configure the system clock; then there
is no need to call the 2 first functions listed above, since SystemCoreClock
variable is updated automatically.
*/
uint32_t SystemCoreClock = 16000000;
const uint8_t AHBPrescTable[16] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 6, 7, 8, 9};
const uint8_t APBPrescTable[8] = {0, 0, 0, 0, 1, 2, 3, 4};
/**
* @}
*/
/** @addtogroup STM32F4xx_System_Private_FunctionPrototypes
* @{
*/
/**
* @}
*/
/** @addtogroup STM32F4xx_System_Private_Functions
* @{
*/
/**
* @brief Setup the microcontroller system
* Initialize the FPU setting, vector table location and External memory
* configuration.
* @param None
* @retval None
*/
void SystemInit(void)
{
/* FPU settings ------------------------------------------------------------*/
#if (__FPU_PRESENT == 1) && (__FPU_USED == 1)
SCB->CPACR |= ((3UL << 10*2)|(3UL << 11*2)); /* set CP10 and CP11 Full Access */
#endif
/* Reset the RCC clock configuration to the default reset state ------------*/
/* Set HSION bit */
RCC->CR |= (uint32_t)0x00000001;
/* Reset CFGR register */
RCC->CFGR = 0x00000000;
/* Reset HSEON, CSSON and PLLON bits */
RCC->CR &= (uint32_t)0xFEF6FFFF;
/* Reset PLLCFGR register */
RCC->PLLCFGR = 0x24003010;
/* Reset HSEBYP bit */
RCC->CR &= (uint32_t)0xFFFBFFFF;
/* Disable all interrupts */
RCC->CIR = 0x00000000;
/* Configure the Vector Table location add offset address ------------------*/
#ifdef VECT_TAB_SRAM
SCB->VTOR = SRAM_BASE | VECT_TAB_OFFSET; /* Vector Table Relocation in Internal SRAM */
#else
SCB->VTOR = FLASH_BASE | VECT_TAB_OFFSET; /* Vector Table Relocation in Internal FLASH */
#endif
}
/**
* @brief Update SystemCoreClock variable according to Clock Register Values.
* The SystemCoreClock variable contains the core clock (HCLK), it can
* be used by the user application to setup the SysTick timer or configure
* other parameters.
*
* @note 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.
*
* - The result of this function could be not correct when using fractional
* value for HSE crystal.
*
* @param None
* @retval None
*/
void SystemCoreClockUpdate(void)
{
uint32_t tmp = 0, pllvco = 0, pllp = 2, pllsource = 0, pllm = 2;
/* Get SYSCLK source -------------------------------------------------------*/
tmp = RCC->CFGR & RCC_CFGR_SWS;
switch (tmp)
{
case 0x00: /* HSI used as system clock source */
SystemCoreClock = HSI_VALUE;
break;
case 0x04: /* HSE used as system clock source */
SystemCoreClock = HSE_VALUE;
break;
case 0x08: /* PLL used as system clock source */
/* PLL_VCO = (HSE_VALUE or HSI_VALUE / PLL_M) * PLL_N
SYSCLK = PLL_VCO / PLL_P
*/
pllsource = (RCC->PLLCFGR & RCC_PLLCFGR_PLLSRC) >> 22;
pllm = RCC->PLLCFGR & RCC_PLLCFGR_PLLM;
if (pllsource != 0)
{
/* HSE used as PLL clock source */
pllvco = (HSE_VALUE / pllm) * ((RCC->PLLCFGR & RCC_PLLCFGR_PLLN) >> 6);
}
else
{
/* HSI used as PLL clock source */
pllvco = (HSI_VALUE / pllm) * ((RCC->PLLCFGR & RCC_PLLCFGR_PLLN) >> 6);
}
pllp = (((RCC->PLLCFGR & RCC_PLLCFGR_PLLP) >>16) + 1 ) *2;
SystemCoreClock = pllvco/pllp;
break;
default:
SystemCoreClock = HSI_VALUE;
break;
}
/* Compute HCLK frequency --------------------------------------------------*/
/* Get HCLK prescaler */
tmp = AHBPrescTable[((RCC->CFGR & RCC_CFGR_HPRE) >> 4)];
/* HCLK frequency */
SystemCoreClock >>= tmp;
}
/**
* @}
*/
/**
* @}
*/
/**
* @}
*/
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