/**
??******************************************************************************
??*?@file????system_stm32f4xx.c
??*?@author??MCD?Application?Team
??*?@version?V1.8.0
??*?@date????09-November-2016
??*?@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）?????????????????????

?屬性????????????大小?????日期????時(shí)間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2018-08-02?11:02??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\
?????目錄???????????0??2018-07-30?12:47??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\
?????目錄???????????0??2018-07-30?12:47??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\
?????文件??????172641??2016-11-05?01:33??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\CMSIS_END_USER_LICENCE_AGREEMENT.pdf
?????文件??????178493??2016-11-05?01:33??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\CMSIS_END_USER_LICENCE_AGREEMENT.rtf
?????目錄???????????0??2018-07-30?12:47??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\
?????目錄???????????0??2018-07-30?12:47??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\
?????目錄???????????0??2018-07-30?12:47??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\
?????目錄???????????0??2018-07-30?12:47??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\ARM\
?????文件?????????149??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\ARM\Abstract.txt
?????文件????????8440??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\ARM\arm_class_marks_example_f32.c
?????目錄???????????0??2018-07-30?12:47??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\GCC\
?????文件?????????149??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\GCC\Abstract.txt
?????目錄???????????0??2018-07-30?12:47??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\GCC\Startup\
?????文件????????4292??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\GCC\Startup\ARMCMx.ld
?????文件???????10480??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\GCC\Startup\startup_ARMCM0.S
?????文件???????10531??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\GCC\Startup\startup_ARMCM3.S
?????文件???????10531??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\GCC\Startup\startup_ARMCM4.S
?????文件????????3197??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\GCC\Startup\system_ARMCM0.c
?????文件????????3281??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\GCC\Startup\system_ARMCM3.c
?????文件????????3594??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\GCC\Startup\system_ARMCM4.c
?????文件????????8440??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_class_marks_example\GCC\arm_class_marks_example_f32.c
?????目錄???????????0??2018-07-30?12:47??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_convolution_example\
?????目錄???????????0??2018-07-30?12:47??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_convolution_example\ARM\
?????文件?????????149??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_convolution_example\ARM\Abstract.txt
?????文件???????11097??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_convolution_example\ARM\arm_convolution_example_f32.c
?????文件???????10962??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_convolution_example\ARM\math_helper.c
?????文件????????3085??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_convolution_example\ARM\math_helper.h
?????目錄???????????0??2018-07-30?12:47??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_convolution_example\GCC\
?????文件?????????149??2016-11-05?01:32??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_convolution_example\GCC\Abstract.txt
?????目錄???????????0??2018-07-30?12:47??STM32F4xx_DSP_StdPeriph_Lib_V1.8.0\Libraries\CMSIS\DSP_Lib\Examples\arm_convolution_example\GCC\Startup\
............此處省略3649個(gè)文件信息