system_stm32f0xx.c


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/**

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  ******************************************************************************

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  * @file    system_stm32f0xx.c

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  * @author  MCD Application Team

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  * @brief   CMSIS Cortex-M0 Device Peripheral Access Layer System Source File.

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  *

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  * 1. This file provides two functions and one global variable to be called from

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  *    user application:

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  *      - SystemInit(): This function is called at startup just after reset and 

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  *                      before branch to main program. This call is made inside

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  *                      the "startup_stm32f0xx.s" file.

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  *

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  *      - SystemCoreClock variable: Contains the core clock (HCLK), it can be used

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  *                                  by the user application to setup the SysTick

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  *                                  timer or configure other parameters.

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  *

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  *      - SystemCoreClockUpdate(): Updates the variable SystemCoreClock and must

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  *                                 be called whenever the core clock is changed

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  *                                 during program execution.

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  *

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  *

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  ******************************************************************************

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  * @attention

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  *

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  * <h2><center>&copy; Copyright (c) 2016 STMicroelectronics.

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  * All rights reserved.</center></h2>

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  *

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  * This software component is licensed by ST under BSD 3-Clause license,

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  * the "License"; You may not use this file except in compliance with the

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  * License. You may obtain a copy of the License at:

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  *                        opensource.org/licenses/BSD-3-Clause

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  *

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  ******************************************************************************

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  */

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/** @addtogroup CMSIS

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  * @{

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  */

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/** @addtogroup stm32f0xx_system

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  * @{

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  */

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/** @addtogroup STM32F0xx_System_Private_Includes

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  * @{

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  */

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#include "stm32f0xx.h"

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/**

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  * @}

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  */

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/** @addtogroup STM32F0xx_System_Private_TypesDefinitions

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  * @{

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  */

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/**

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  * @}

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  */

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/** @addtogroup STM32F0xx_System_Private_Defines

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  * @{

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  */

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#if !defined  (HSE_VALUE) 

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  #define HSE_VALUE    ((uint32_t)8000000) /*!< Default value of the External oscillator in Hz.

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                                                This value can be provided and adapted by the user application. */

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#endif /* HSE_VALUE */

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#if !defined  (HSI_VALUE)

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  #define HSI_VALUE    ((uint32_t)8000000) /*!< Default value of the Internal oscillator in Hz.

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                                                This value can be provided and adapted by the user application. */

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#endif /* HSI_VALUE */

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#if !defined (HSI48_VALUE)

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#define HSI48_VALUE    ((uint32_t)48000000) /*!< Default value of the HSI48 Internal oscillator in Hz.

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                                                 This value can be provided and adapted by the user application. */

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#endif /* HSI48_VALUE */

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/**

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  * @}

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  */

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/** @addtogroup STM32F0xx_System_Private_Macros

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  * @{

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  */

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/**

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  * @}

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  */

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/** @addtogroup STM32F0xx_System_Private_Variables

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  * @{

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  */

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  /* This variable is updated in three ways:

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      1) by calling CMSIS function SystemCoreClockUpdate()

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      2) by calling HAL API function HAL_RCC_GetHCLKFreq()

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      3) each time HAL_RCC_ClockConfig() is called to configure the system clock frequency

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         Note: If you use this function to configure the system clock; then there

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               is no need to call the 2 first functions listed above, since SystemCoreClock

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               variable is updated automatically.

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  */

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uint32_t SystemCoreClock = 8000000;

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const uint8_t AHBPrescTable[16] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 6, 7, 8, 9};

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const uint8_t APBPrescTable[8]  = {0, 0, 0, 0, 1, 2, 3, 4};

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/**

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  * @}

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  */

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/** @addtogroup STM32F0xx_System_Private_FunctionPrototypes

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  * @{

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  */

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/**

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  * @}

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  */

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/** @addtogroup STM32F0xx_System_Private_Functions

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  * @{

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  */

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/**

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  * @brief  Setup the microcontroller system

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  * @param  None

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  * @retval None

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  */

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void SystemInit(void)

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{

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  /* NOTE :SystemInit(): This function is called at startup just after reset and 

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                         before branch to main program. This call is made inside

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                         the "startup_stm32f0xx.s" file.

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                         User can setups the default system clock (System clock source, PLL Multiplier

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                         and Divider factors, AHB/APBx prescalers and Flash settings).

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   */

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}

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/**

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   * @brief  Update SystemCoreClock variable according to Clock Register Values.

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  *         The SystemCoreClock variable contains the core clock (HCLK), it can

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  *         be used by the user application to setup the SysTick timer or configure

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  *         other parameters.

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  *

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  * @note   Each time the core clock (HCLK) changes, this function must be called

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  *         to update SystemCoreClock variable value. Otherwise, any configuration

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  *         based on this variable will be incorrect.

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  *

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  * @note   - The system frequency computed by this function is not the real

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  *           frequency in the chip. It is calculated based on the predefined

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  *           constant and the selected clock source:

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  *

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  *           - If SYSCLK source is HSI, SystemCoreClock will contain the HSI_VALUE(*)

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  *

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  *           - If SYSCLK source is HSE, SystemCoreClock will contain the HSE_VALUE(**)

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  *

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  *           - If SYSCLK source is PLL, SystemCoreClock will contain the HSE_VALUE(**)

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  *             or HSI_VALUE(*) multiplied/divided by the PLL factors.

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  *

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  *         (*) HSI_VALUE is a constant defined in stm32f0xx_hal_conf.h file (default value

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  *             8 MHz) but the real value may vary depending on the variations

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  *             in voltage and temperature.

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  *

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  *         (**) HSE_VALUE is a constant defined in stm32f0xx_hal_conf.h file (its value

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  *              depends on the application requirements), user has to ensure that HSE_VALUE

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  *              is same as the real frequency of the crystal used. Otherwise, this function

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  *              may have wrong result.

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  *

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  *         - The result of this function could be not correct when using fractional

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  *           value for HSE crystal.

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  *

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  * @param  None

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  * @retval None

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  */

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void SystemCoreClockUpdate (void)

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{

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  uint32_t tmp = 0, pllmull = 0, pllsource = 0, predivfactor = 0;

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  /* Get SYSCLK source -------------------------------------------------------*/

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  tmp = RCC->CFGR & RCC_CFGR_SWS;

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  switch (tmp)

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  {

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    case RCC_CFGR_SWS_HSI:  /* HSI used as system clock */

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      SystemCoreClock = HSI_VALUE;

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      break;

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    case RCC_CFGR_SWS_HSE:  /* HSE used as system clock */

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      SystemCoreClock = HSE_VALUE;

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      break;

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    case RCC_CFGR_SWS_PLL:  /* PLL used as system clock */

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      /* Get PLL clock source and multiplication factor ----------------------*/

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      pllmull = RCC->CFGR & RCC_CFGR_PLLMUL;

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      pllsource = RCC->CFGR & RCC_CFGR_PLLSRC;

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      pllmull = ( pllmull >> 18) + 2;

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      predivfactor = (RCC->CFGR2 & RCC_CFGR2_PREDIV) + 1;

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      if (pllsource == RCC_CFGR_PLLSRC_HSE_PREDIV)

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      {

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        /* HSE used as PLL clock source : SystemCoreClock = HSE/PREDIV * PLLMUL */

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        SystemCoreClock = (HSE_VALUE/predivfactor) * pllmull;

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      }

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#if defined(STM32F042x6) || defined(STM32F048xx) || defined(STM32F072xB) || defined(STM32F078xx) || defined(STM32F091xC) || defined(STM32F098xx)

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      else if (pllsource == RCC_CFGR_PLLSRC_HSI48_PREDIV)

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      {

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        /* HSI48 used as PLL clock source : SystemCoreClock = HSI48/PREDIV * PLLMUL */

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        SystemCoreClock = (HSI48_VALUE/predivfactor) * pllmull;

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      }

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#endif /* STM32F042x6 || STM32F048xx || STM32F072xB || STM32F078xx || STM32F091xC || STM32F098xx */

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      else

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      {

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#if defined(STM32F042x6) || defined(STM32F048xx)  || defined(STM32F070x6) \

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 || defined(STM32F078xx) || defined(STM32F071xB)  || defined(STM32F072xB) \

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 || defined(STM32F070xB) || defined(STM32F091xC) || defined(STM32F098xx)  || defined(STM32F030xC)

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        /* HSI used as PLL clock source : SystemCoreClock = HSI/PREDIV * PLLMUL */

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        SystemCoreClock = (HSI_VALUE/predivfactor) * pllmull;

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#else

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        /* HSI used as PLL clock source : SystemCoreClock = HSI/2 * PLLMUL */

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        SystemCoreClock = (HSI_VALUE >> 1) * pllmull;

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#endif /* STM32F042x6 || STM32F048xx || STM32F070x6 || 

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          STM32F071xB || STM32F072xB || STM32F078xx || STM32F070xB ||

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          STM32F091xC || STM32F098xx || STM32F030xC */

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      }

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      break;

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    default: /* HSI used as system clock */

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      SystemCoreClock = HSI_VALUE;

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      break;

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  }

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  /* Compute HCLK clock frequency ----------------*/

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  /* Get HCLK prescaler */

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  tmp = AHBPrescTable[((RCC->CFGR & RCC_CFGR_HPRE) >> 4)];

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  /* HCLK clock frequency */

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  SystemCoreClock >>= tmp;

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}

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/**

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  * @}

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  */

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/**

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  * @}

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  */

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/**

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  * @}

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  */

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/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/