stm32f4xx固件库亲测，好使

stm32f4xx固件库，编程必备资料，供大家交流学习使用。

/**
  ******************************************************************************
  * @file    system_stm32f4xx.c
  * @author  MCD Application Team
  * @version V1.4.0
  * @date    04-August-2014
  * @brief   CMSIS Cortex-M4 Device Peripheral Access layer System Source File.
  *          This file contains the system clock configuration for STM32F4xx devices.
  *             
  * 1.  This file provides two functions and one global variable to be called from 
  *     user application:
  *      - SystemInit（）: Setups the system clock （System clock source PLL Multiplier
  *                      and Divider factors AHB/APBx prescalers and Flash settings）
  *                      depending on the configuration made in the clock xls tool. 
  *                      This function is called at startup just after reset and 
  *                      before branch to main program. This call is made inside
  *                      the “startup_stm32f4xx.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.
  *
  * 2. After each device reset the HSI （16 MHz） is used as system clock source.
  *    Then SystemInit（） function is called in “startup_stm32f4xx.s“ file to
  *    configure the system clock before to branch to main program.
  *
  * 3. If the system clock source selected by user fails to startup the SystemInit（）
  *    function will do nothing and HSI still used as system clock source. User can 
  *    add some code to deal with this issue inside the SetSysClock（） function.
  *
  * 4. The default value of HSE crystal is set to 25MHz refer to “HSE_VALUE“ define
  *    in “stm32f4xx.h“ file. When HSE is used as system clock source directly or
  *    through PLL and you are using different crystal you have to adapt the HSE
  *    value to your own configuration.
  *
  * 5. This file configures the system clock as follows:
  *=============================================================================
  *=============================================================================
  *                    Supported STM32F40xxx/41xxx devices
  *-----------------------------------------------------------------------------
  *        System Clock source                    | PLL （HSE）
  *-----------------------------------------------------------------------------
  *        SYSCLK（Hz）                             | 168000000
  *-----------------------------------------------------------------------------
  *        HCLK（Hz）                       

 属性            大小     日期    时间   名称
----------- ---------  ---------- -----  ----
     目录           0  2014-08-05 02:02  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\
     目录           0  2014-08-05 01:59  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\
     目录           0  2014-08-05 01:59  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\
     文件       24914  2014-07-17 21:53  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\CMSIS END USER LICENCE AGREEMENT.pdf
     目录           0  2014-08-05 01:57  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\
     目录           0  2014-08-05 01:57  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\
     目录           0  2014-08-05 01:57  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\
     目录           0  2014-08-05 01:57  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Include\
     文件      704095  2014-08-01 22:30  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Include\stm32f4xx.h
     文件        2233  2014-08-01 22:30  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Include\system_stm32f4xx.h
     文件       36887  2014-08-04 20:07  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Release_Notes.html
     目录           0  2014-08-05 01:57  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\
     目录           0  2014-08-05 01:57  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\
     目录           0  2014-08-05 01:57  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\arm\
     文件       25817  2014-08-02 00:12  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\arm\startup_stm32f401xx.s
     文件       29694  2014-08-02 00:12  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\arm\startup_stm32f40xx.s
     文件       29605  2014-08-02 00:12  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\arm\startup_stm32f40_41xxx.s
     文件       26517  2014-08-02 00:10  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\arm\startup_stm32f411xe.s
     文件       31054  2014-08-02 00:12  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\arm\startup_stm32f427x.s
     文件       30979  2014-08-02 00:12  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\arm\startup_stm32f427_437xx.s
     文件       31134  2014-08-02 00:12  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\arm\startup_stm32f429_439xx.s
     目录           0  2014-08-05 01:57  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\gcc_ride7\
     文件       20646  2014-07-17 21:56  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\gcc_ride7\startup_stm32f401xx.s
     文件       24189  2014-07-17 21:56  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\gcc_ride7\startup_stm32f40xx.s
     文件       24111  2014-07-17 21:56  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\gcc_ride7\startup_stm32f40_41xxx.s
     文件       25817  2014-07-17 21:56  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\gcc_ride7\startup_stm32f427x.s
     文件       25734  2014-07-17 21:56  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\gcc_ride7\startup_stm32f427_437xx.s
     文件       25734  2014-07-17 21:56  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\gcc_ride7\startup_stm32f429_439xx.s
     目录           0  2014-08-05 01:57  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\iar\
     文件       21524  2014-08-02 00:12  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\iar\startup_stm32f401xx.s
     文件       25429  2014-08-02 00:12  STM32F4xx_DSP_StdPeriph_Lib_V1.4.0\Libraries\CMSIS\Device\ST\STM32F4xx\Source\Templates\iar\startup_stm32f40xx.s
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