140 lines
7.1 KiB
C
140 lines
7.1 KiB
C
/**
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******************************************************************************
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* @file system_stm32l4xx.c
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* @author MCD Application Team
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* @brief CMSIS Cortex-M4 Device Peripheral Access Layer System Source File
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*
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* 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_stm32l4xx.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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* After each device reset the MSI (4 MHz) is used as system clock source.
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* Then SystemInit() function is called, in "startup_stm32l4xx.s" file, to
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* configure the system clock before to branch to main program.
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*
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* This file configures the system clock as follows:
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*=============================================================================
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*-----------------------------------------------------------------------------
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* System Clock source | MSI
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*-----------------------------------------------------------------------------
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* SYSCLK(Hz) | 4000000
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*-----------------------------------------------------------------------------
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* HCLK(Hz) | 4000000
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*-----------------------------------------------------------------------------
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* AHB Prescaler | 1
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*-----------------------------------------------------------------------------
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* APB1 Prescaler | 1
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*-----------------------------------------------------------------------------
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* APB2 Prescaler | 1
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*-----------------------------------------------------------------------------
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* PLL_M | 1
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*-----------------------------------------------------------------------------
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* PLL_N | 8
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*-----------------------------------------------------------------------------
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* PLL_P | 7
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*-----------------------------------------------------------------------------
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* PLL_Q | 2
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*-----------------------------------------------------------------------------
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* PLL_R | 2
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*-----------------------------------------------------------------------------
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* PLLSAI1_P | NA
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*-----------------------------------------------------------------------------
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* PLLSAI1_Q | NA
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*-----------------------------------------------------------------------------
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* PLLSAI1_R | NA
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*-----------------------------------------------------------------------------
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* PLLSAI2_P | NA
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*-----------------------------------------------------------------------------
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* PLLSAI2_Q | NA
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*-----------------------------------------------------------------------------
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* PLLSAI2_R | NA
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*-----------------------------------------------------------------------------
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* Require 48MHz for USB OTG FS, | Disabled
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* SDIO and RNG clock |
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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>© COPYRIGHT(c) 2017 STMicroelectronics</center></h2>
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*
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* Redistribution and use in source and binary forms, with or without modification,
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* are permitted provided that the following conditions are met:
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* 1. Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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* 3. Neither the name of STMicroelectronics nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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******************************************************************************
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*/
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#include "stm32l4xx.h"
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#if !defined (HSE_VALUE)
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#define HSE_VALUE 8000000U /*!< Value of the External oscillator in Hz */
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#endif /* HSE_VALUE */
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#if !defined (MSI_VALUE)
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#define MSI_VALUE 4000000U /*!< Value of the Internal oscillator in Hz*/
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#endif /* MSI_VALUE */
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#if !defined (HSI_VALUE)
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#define HSI_VALUE 16000000U /*!< Value of the Internal oscillator in Hz*/
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#endif /* HSI_VALUE */
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uint32_t SystemCoreClock = 4000000U;
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const uint8_t AHBPrescTable[16] = {0U, 0U, 0U, 0U, 0U, 0U, 0U, 0U, 1U, 2U, 3U, 4U, 6U, 7U, 8U, 9U};
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const uint8_t APBPrescTable[8] = {0U, 0U, 0U, 0U, 1U, 2U, 3U, 4U};
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const uint32_t MSIRangeTable[12] = {100000U, 200000U, 400000U, 800000U, 1000000U, 2000000U, \
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4000000U, 8000000U, 16000000U, 24000000U, 32000000U, 48000000U};
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void SystemInit(void) {
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/* Reset the RCC clock configuration to the default reset state ------------*/
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/* Set MSION bit */
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RCC->CR |= RCC_CR_MSION;
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/* Reset CFGR register */
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RCC->CFGR = 0x00000000U;
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/* Reset HSEON, CSSON , HSION, and PLLON bits */
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RCC->CR &= 0xEAF6FFFFU;
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/* Reset PLLCFGR register */
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RCC->PLLCFGR = 0x00001000U;
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/* Reset HSEBYP bit */
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RCC->CR &= 0xFFFBFFFFU;
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/* Disable all interrupts */
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RCC->CIER = 0x00000000U;
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}
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/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
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