/**
******************************************************************************
* @file system_stm32g4xx.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_stm32g4xx.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 HSI (16 MHz) is used as system clock source.
* Then SystemInit() function is called, in "startup_stm32g4xx.s" file, to
* configure the system clock before to branch to main program.
*
* This file configures the system clock as follows:
*=============================================================================
*-----------------------------------------------------------------------------
* System Clock source | HSI
*-----------------------------------------------------------------------------
* SYSCLK(Hz) | 16000000
*-----------------------------------------------------------------------------
* HCLK(Hz) | 16000000
*-----------------------------------------------------------------------------
* AHB Prescaler | 1
*-----------------------------------------------------------------------------
* APB1 Prescaler | 1
*-----------------------------------------------------------------------------
* APB2 Prescaler | 1
*-----------------------------------------------------------------------------
* PLL_M | 1
*-----------------------------------------------------------------------------
* PLL_N | 16
*-----------------------------------------------------------------------------
* PLL_P | 7
*-----------------------------------------------------------------------------
* PLL_Q | 2
*-----------------------------------------------------------------------------
* PLL_R | 2
*-----------------------------------------------------------------------------
* Require 48MHz for RNG | Disabled
*-----------------------------------------------------------------------------
*=============================================================================
******************************************************************************
* @attention
*
* <h2><center>© Copyright (c) 2019 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 stm32g4xx_system
* @{
*/
/** @addtogroup STM32G4xx_System_Private_Includes
* @{
*/
#include "stm32g4xx.h"
#if !defined (HSE_VALUE)
#define HSE_VALUE 24000000U /*!< Value of the External oscillator in Hz */
#endif /* HSE_VALUE */
#if !defined (HSI_VALUE)
#define HSI_VALUE 16000000U /*!< Value of the Internal oscillator in Hz*/
#endif /* HSI_VALUE */
/**
* @}
*/
/** @addtogroup STM32G4xx_System_Private_TypesDefinitions
* @{
*/
/**
* @}
*/
/** @addtogroup STM32G4xx_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 0x00UL /*!< Vector Table base offset field.
This value must be a multiple of 0x200. */
/******************************************************************************/
/**
* @}
*/
/** @addtogroup STM32G4xx_System_Private_Macros
* @{
*/
/**
* @}
*/
/** @addtogroup STM32G4xx_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 = HSI_VALUE;
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};
/**
* @}
*/
/** @addtogroup STM32G4xx_System_Private_FunctionPrototypes
* @{
*/
/**
* @}
*/
/** @addtogroup STM32G4xx_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
/* 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
#include "nvic_addr.h" // MBED
SCB->VTOR = NVIC_FLASH_VECTOR_ADDRESS; // MBED
#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 stm32g4xx_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 stm32g4xx_hal.h file (default value
* 24 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, pllvco, pllr, pllsource, pllm;
/* Get SYSCLK source -------------------------------------------------------*/
switch (RCC->CFGR & RCC_CFGR_SWS)
{
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 / PLLM) * PLLN
SYSCLK = PLL_VCO / PLLR
*/
pllsource = (RCC->PLLCFGR & RCC_PLLCFGR_PLLSRC);
pllm = ((RCC->PLLCFGR & RCC_PLLCFGR_PLLM) >> 4) + 1U ;
if (pllsource == 0x02UL) /* HSI used as PLL clock source */
{
pllvco = (HSI_VALUE / pllm);
}
else /* HSE used as PLL clock source */
{
pllvco = (HSE_VALUE / pllm);
}
pllvco = pllvco * ((RCC->PLLCFGR & RCC_PLLCFGR_PLLN) >> 8);
pllr = (((RCC->PLLCFGR & RCC_PLLCFGR_PLLR) >> 25) + 1U) * 2U;
SystemCoreClock = pllvco/pllr;
break;
default:
break;
}
/* Compute HCLK clock frequency --------------------------------------------*/
/* Get HCLK prescaler */
tmp = AHBPrescTable[((RCC->CFGR & RCC_CFGR_HPRE) >> 4)];
/* HCLK clock frequency */
SystemCoreClock >>= tmp;
}
/**
* @}
*/
/**
* @}
*/
/**
* @}
*/
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
