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pigweed / third_party / github / STMicroelectronics / cmsis_device_l0 / 78696f4f79cf51c8b32d0aa5c199a04f57ee4b27 / . / Source / Templates / system_stm32l0xx.c
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/**
******************************************************************************
* @file system_stm32l0xx.c
* @author MCD Application Team
* @brief CMSIS Cortex-M0+ 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_stm32l0xx.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
*
* <h2><center>&copy; Copyright(c) 2016 STMicroelectronics.
* All rights reserved.</center></h2>
*
* This software component is licensed by ST under BSD 3-Clause license,
* the "License"; You may not use this file except in compliance with the
* License. You may obtain a copy of the License at:
* opensource.org/licenses/BSD-3-Clause
*
******************************************************************************
*/
/** @addtogroup CMSIS
* @{
*/
/** @addtogroup stm32l0xx_system
* @{
*/
/** @addtogroup STM32L0xx_System_Private_Includes
* @{
*/
#include "stm32l0xx.h"
#if !defined (HSE_VALUE)
#define HSE_VALUE ((uint32_t)8000000U) /*!< Value of the External oscillator in Hz */
#endif /* HSE_VALUE */
#if !defined (MSI_VALUE)
#define MSI_VALUE ((uint32_t)2097152U) /*!< Value of the Internal oscillator in Hz*/
#endif /* MSI_VALUE */
#if !defined (HSI_VALUE)
#define HSI_VALUE ((uint32_t)16000000U) /*!< Value of the Internal oscillator in Hz*/
#endif /* HSI_VALUE */
/**
* @}
*/
/** @addtogroup STM32L0xx_System_Private_TypesDefinitions
* @{
*/
/**
* @}
*/
/** @addtogroup STM32L0xx_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 0x00U /*!< Vector Table base offset field.
This value must be a multiple of 0x100. */
/******************************************************************************/
/**
* @}
*/
/** @addtogroup STM32L0xx_System_Private_Macros
* @{
*/
/**
* @}
*/
/** @addtogroup STM32L0xx_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 = 2097152U; /* 32.768 kHz * 2^6 */
const uint8_t AHBPrescTable[16] = {0U, 0U, 0U, 0U, 0U, 0U, 0U, 0U, 1U, 2U, 3U, 4U, 6U, 7U, 8U, 9U};
const uint8_t APBPrescTable[8] = {0U, 0U, 0U, 0U, 1U, 2U, 3U, 4U};
const uint8_t PLLMulTable[9] = {3U, 4U, 6U, 8U, 12U, 16U, 24U, 32U, 48U};
/**
* @}
*/
/** @addtogroup STM32L0xx_System_Private_FunctionPrototypes
* @{
*/
/**
* @}
*/
/** @addtogroup STM32L0xx_System_Private_Functions
* @{
*/
/**
* @brief Setup the microcontroller system.
* @param None
* @retval None
*/
void SystemInit (void)
{
/*!< Set MSION bit */
RCC->CR |= (uint32_t)0x00000100U;
/*!< Reset SW[1:0], HPRE[3:0], PPRE1[2:0], PPRE2[2:0], MCOSEL[2:0] and MCOPRE[2:0] bits */
RCC->CFGR &= (uint32_t) 0x88FF400CU;
/*!< Reset HSION, HSIDIVEN, HSEON, CSSON and PLLON bits */
RCC->CR &= (uint32_t)0xFEF6FFF6U;
/*!< Reset HSI48ON bit */
RCC->CRRCR &= (uint32_t)0xFFFFFFFEU;
/*!< Reset HSEBYP bit */
RCC->CR &= (uint32_t)0xFFFBFFFFU;
/*!< Reset PLLSRC, PLLMUL[3:0] and PLLDIV[1:0] bits */
RCC->CFGR &= (uint32_t)0xFF02FFFFU;
/*!< Disable all interrupts */
RCC->CIER = 0x00000000U;
/* 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 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 MSI, SystemCoreClock will contain the MSI
* value as defined by the MSI range.
*
* - 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 stm32l0xx_hal.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 stm32l0xx_hal.h file (default value
* 8 MHz), 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 = 0U, pllmul = 0U, plldiv = 0U, pllsource = 0U, msirange = 0U;
/* Get SYSCLK source -------------------------------------------------------*/
tmp = RCC->CFGR & RCC_CFGR_SWS;
switch (tmp)
{
case 0x00U: /* MSI used as system clock */
msirange = (RCC->ICSCR & RCC_ICSCR_MSIRANGE) >> RCC_ICSCR_MSIRANGE_Pos;
SystemCoreClock = (32768U * (1U << (msirange + 1U)));
break;
case 0x04U: /* HSI used as system clock */
if ((RCC->CR & RCC_CR_HSIDIVF) != 0U)
{
SystemCoreClock = HSI_VALUE / 4U;
}
else
{
SystemCoreClock = HSI_VALUE;
}
break;
case 0x08U: /* HSE used as system clock */
SystemCoreClock = HSE_VALUE;
break;
default: /* PLL used as system clock */
/* Get PLL clock source and multiplication factor ----------------------*/
pllmul = RCC->CFGR & RCC_CFGR_PLLMUL;
plldiv = RCC->CFGR & RCC_CFGR_PLLDIV;
pllmul = PLLMulTable[(pllmul >> RCC_CFGR_PLLMUL_Pos)];
plldiv = (plldiv >> RCC_CFGR_PLLDIV_Pos) + 1U;
pllsource = RCC->CFGR & RCC_CFGR_PLLSRC;
if (pllsource == 0x00U)
{
/* HSI oscillator clock selected as PLL clock entry */
if ((RCC->CR & RCC_CR_HSIDIVF) != 0U)
{
SystemCoreClock = (((HSI_VALUE / 4U) * pllmul) / plldiv);
}
else
{
SystemCoreClock = (((HSI_VALUE) * pllmul) / plldiv);
}
}
else
{
/* HSE selected as PLL clock entry */
SystemCoreClock = (((HSE_VALUE) * pllmul) / plldiv);
}
break;
}
/* Compute HCLK clock frequency --------------------------------------------*/
/* Get HCLK prescaler */
tmp = AHBPrescTable[((RCC->CFGR & RCC_CFGR_HPRE) >> RCC_CFGR_HPRE_Pos)];
/* HCLK clock frequency */
SystemCoreClock >>= tmp;
}
/**
* @}
*/
/**
* @}
*/
/**
* @}
*/
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/