/**
??******************************************************************************
??*?@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）???????????????????????

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2019-01-09?18:44??Code?1.0\
?????目錄???????????0??2019-01-04?14:44??Code?1.0\CMSIS\
?????文件??????114403??2016-11-05?01:33??Code?1.0\CMSIS\core_cm4.h
?????文件???????18323??2016-11-05?01:33??Code?1.0\CMSIS\core_cmFunc.h
?????文件???????27908??2016-11-05?01:33??Code?1.0\CMSIS\core_cmInstr.h
?????文件???????22947??2016-11-05?01:33??Code?1.0\CMSIS\core_cmSimd.h
?????目錄???????????0??2019-01-04?14:44??Code?1.0\CMSIS\STARTUP\
?????文件???????29605??2016-04-15?21:58??Code?1.0\CMSIS\STARTUP\startup_stm32f40_41xxx.s
?????文件??????940127??2016-11-07?23:03??Code?1.0\CMSIS\stm32f4xx.h
?????文件???????47778??2019-01-09?10:24??Code?1.0\CMSIS\system_stm32f4xx.c
?????文件????????2235??2016-11-07?23:03??Code?1.0\CMSIS\system_stm32f4xx.h
?????目錄???????????0??2019-01-17?14:04??Code?1.0\PROJECT\
?????目錄???????????0??2019-01-04?14:46??Code?1.0\PROJECT\DebugConfig\
?????文件????????2851??2017-11-21?16:21??Code?1.0\PROJECT\DebugConfig\Target_1_STM32F407VETx.dbgconf
?????目錄???????????0??2019-01-04?14:54??Code?1.0\PROJECT\Listings\
?????文件??????130771??2019-01-17?11:27??Code?1.0\PROJECT\Listings\Project.map
?????文件???????79374??2019-01-12?16:43??Code?1.0\PROJECT\Listings\startup_stm32f40_41xxx.lst
?????目錄???????????0??2019-01-17?11:27??Code?1.0\PROJECT\objects\
?????文件??????453274??2019-01-12?16:43??Code?1.0\PROJECT\objects\dcmi.crf
?????文件????????2242??2019-01-12?16:43??Code?1.0\PROJECT\objects\dcmi.d
?????文件??????494764??2019-01-12?16:43??Code?1.0\PROJECT\objects\dcmi.o
?????文件??????451784??2019-01-12?16:43??Code?1.0\PROJECT\objects\delay.crf
?????文件????????2284??2019-01-12?16:43??Code?1.0\PROJECT\objects\delay.d
?????文件??????494160??2019-01-12?16:43??Code?1.0\PROJECT\objects\delay.o
?????文件??????451453??2019-01-12?16:43??Code?1.0\PROJECT\objects\led.crf
?????文件????????2327??2019-01-12?16:43??Code?1.0\PROJECT\objects\led.d
?????文件??????489192??2019-01-12?16:43??Code?1.0\PROJECT\objects\led.o
?????文件??????458833??2019-01-17?11:27??Code?1.0\PROJECT\objects\main.crf
?????文件????????2365??2019-01-17?11:27??Code?1.0\PROJECT\objects\main.d
?????文件??????500032??2019-01-17?11:27??Code?1.0\PROJECT\objects\main.o
?????文件??????452180??2019-01-12?16:43??Code?1.0\PROJECT\objects\misc.crf
............此處省略279個文件信息