/** ****************************************************************************** * @file system_stm32l4xx.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_stm32l4xx.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. * * After each device reset the MSI (4 MHz) is used as system clock source. * Then SystemInit() function is called, in "startup_stm32l4xx.s" file, to * configure the system clock before to branch to main program. * * This file configures the system clock as follows: *============================================================================= *----------------------------------------------------------------------------- * System Clock source | MSI *----------------------------------------------------------------------------- * SYSCLK(Hz) | 4000000 *----------------------------------------------------------------------------- * HCLK(Hz) | 4000000 *----------------------------------------------------------------------------- * AHB Prescaler | 1 *----------------------------------------------------------------------------- * APB1 Prescaler | 1 *----------------------------------------------------------------------------- * APB2 Prescaler | 1 *----------------------------------------------------------------------------- * PLL_M | 1 *----------------------------------------------------------------------------- * PLL_N | 8 *----------------------------------------------------------------------------- * PLL_P | 7 *----------------------------------------------------------------------------- * PLL_Q | 2 *----------------------------------------------------------------------------- * PLL_R | 2 *----------------------------------------------------------------------------- * PLLSAI1_P | NA *----------------------------------------------------------------------------- * PLLSAI1_Q | NA *----------------------------------------------------------------------------- * PLLSAI1_R | NA *----------------------------------------------------------------------------- * PLLSAI2_P | NA *----------------------------------------------------------------------------- * PLLSAI2_Q | NA *----------------------------------------------------------------------------- * PLLSAI2_R | NA *----------------------------------------------------------------------------- * Require 48MHz for USB OTG FS, | Disabled * SDIO and RNG clock | *----------------------------------------------------------------------------- *============================================================================= ****************************************************************************** * @attention * *

© Copyright (c) 2017 STMicroelectronics. * All rights reserved.

* * 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 stm32l4xx_system * @{ */ /** @addtogroup STM32L4xx_System_Private_Includes * @{ */ #include "stm32l4xx.h" #if !defined(HSE_VALUE) #define HSE_VALUE 8000000U /*!< Value of the External oscillator in Hz */ #endif /* HSE_VALUE */ #if !defined(MSI_VALUE) #define MSI_VALUE 4000000U /*!< Value of the Internal oscillator in Hz*/ #endif /* MSI_VALUE */ #if !defined(HSI_VALUE) #define HSI_VALUE 16000000U /*!< Value of the Internal oscillator in Hz*/ #endif /* HSI_VALUE */ /** * @} */ /** @addtogroup STM32L4xx_System_Private_TypesDefinitions * @{ */ /** * @} */ /** @addtogroup STM32L4xx_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 STM32L4xx_System_Private_Macros * @{ */ /** * @} */ /** @addtogroup STM32L4xx_System_Private_Variables * @{ */ /* The SystemCoreClock 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 = 4000000U; 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 uint32_t MSIRangeTable[12] = { 100000U, 200000U, 400000U, 800000U, 1000000U, 2000000U, 4000000U, 8000000U, 16000000U, 24000000U, 32000000U, 48000000U}; /** * @} */ /** @addtogroup STM32L4xx_System_Private_FunctionPrototypes * @{ */ /** * @} */ /** @addtogroup STM32L4xx_System_Private_Functions * @{ */ /** * @brief Setup the microcontroller system. * @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 MSION bit */ RCC->CR |= RCC_CR_MSION; /* Reset CFGR register */ RCC->CFGR = 0x00000000U; /* Reset HSEON, CSSON , HSION, and PLLON bits */ RCC->CR &= 0xEAF6FFFFU; /* Reset PLLCFGR register */ RCC->PLLCFGR = 0x00001000U; /* Reset HSEBYP bit */ RCC->CR &= 0xFFFBFFFFU; /* 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 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 MSI, SystemCoreClock will contain the MSI_VALUE(*) * * - 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(*) or MSI_VALUE(*) multiplied/divided by the PLL factors. * * (*) MSI_VALUE is a constant defined in stm32l4xx_hal.h file (default value * 4 MHz) but the real value may vary depending on the variations * in voltage and temperature. * * (**) HSI_VALUE is a constant defined in stm32l4xx_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 stm32l4xx_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, msirange = 0U, pllvco = 0U, pllr = 2U, pllsource = 0U, pllm = 2U; /* Get MSI Range frequency--------------------------------------------------*/ if((RCC->CR & RCC_CR_MSIRGSEL) == RESET) { /* MSISRANGE from RCC_CSR applies */ msirange = (RCC->CSR & RCC_CSR_MSISRANGE) >> 8U; } else { /* MSIRANGE from RCC_CR applies */ msirange = (RCC->CR & RCC_CR_MSIRANGE) >> 4U; } /*MSI frequency range in HZ*/ msirange = MSIRangeTable[msirange]; /* Get SYSCLK source -------------------------------------------------------*/ switch(RCC->CFGR & RCC_CFGR_SWS) { case 0x00: /* MSI used as system clock source */ SystemCoreClock = msirange; break; case 0x04: /* HSI used as system clock source */ SystemCoreClock = HSI_VALUE; break; case 0x08: /* HSE used as system clock source */ SystemCoreClock = HSE_VALUE; break; case 0x0C: /* PLL used as system clock source */ /* PLL_VCO = (HSE_VALUE or HSI_VALUE or MSI_VALUE/ PLLM) * PLLN SYSCLK = PLL_VCO / PLLR */ pllsource = (RCC->PLLCFGR & RCC_PLLCFGR_PLLSRC); pllm = ((RCC->PLLCFGR & RCC_PLLCFGR_PLLM) >> 4U) + 1U; switch(pllsource) { case 0x02: /* HSI used as PLL clock source */ pllvco = (HSI_VALUE / pllm); break; case 0x03: /* HSE used as PLL clock source */ pllvco = (HSE_VALUE / pllm); break; default: /* MSI used as PLL clock source */ pllvco = (msirange / pllm); break; } pllvco = pllvco * ((RCC->PLLCFGR & RCC_PLLCFGR_PLLN) >> 8U); pllr = (((RCC->PLLCFGR & RCC_PLLCFGR_PLLR) >> 25U) + 1U) * 2U; SystemCoreClock = pllvco / pllr; break; default: SystemCoreClock = msirange; break; } /* Compute HCLK clock frequency --------------------------------------------*/ /* Get HCLK prescaler */ tmp = AHBPrescTable[((RCC->CFGR & RCC_CFGR_HPRE) >> 4U)]; /* HCLK clock frequency */ SystemCoreClock >>= tmp; } /** * @} */ /** * @} */ /** * @} */ /************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/