/**
??******************************************************************************
??*?@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
-----------?---------??----------?-----??----

?????文件?????109873??2014-05-27?13:46??XYD_Watch\CMSIS\core_cm4.h

?????文件??????22735??2014-07-17?21:52??XYD_Watch\CMSIS\core_cm4_simd.h

?????文件??????17146??2014-07-17?21:52??XYD_Watch\CMSIS\core_cmFunc.h

?????文件??????20513??2014-07-17?21:52??XYD_Watch\CMSIS\core_cmInstr.h

?????文件??????29605??2017-09-25?23:22??XYD_Watch\CMSIS\startup_stm32f40_41xxx.s

?????文件?????704119??2016-08-03?09:31??XYD_Watch\CMSIS\stm32f4xx.h

?????文件?????704095??2014-08-01?22:30??XYD_Watch\CMSIS\stm32f4xx.h~RF1fa727.TMP

?????文件??????47782??2014-08-02?00:06??XYD_Watch\CMSIS\system_stm32f4xx.c

?????文件???????2233??2014-08-01?22:30??XYD_Watch\CMSIS\system_stm32f4xx.h

?????文件???????1527??2015-10-27?12:06??XYD_Watch\DebugConfig\Target_1_STM32F411CEUx.dbgconf

?????文件????????339??2018-09-22?09:25??XYD_Watch\EventRecorderStub.scvd

?????文件??????22434??2019-04-15?11:12??XYD_Watch\Listings\os_cpu_a.lst

?????文件??????77015??2019-04-15?11:12??XYD_Watch\Listings\startup_stm32f40_41xxx.lst

?????文件?????263325??2019-04-15?11:12??XYD_Watch\Listings\XYD_Watch.map

?????文件?????234960??2019-04-15?11:12??XYD_Watch\objects\adc.crf

?????文件????????407??2019-04-15?11:12??XYD_Watch\objects\adc.d

?????文件?????250084??2019-04-15?11:12??XYD_Watch\objects\adc.o

?????文件?????288263??2019-04-15?11:12??XYD_Watch\objects\app_handler.crf

?????文件???????1875??2019-04-15?11:12??XYD_Watch\objects\app_handler.d

?????文件?????298964??2019-04-15?11:12??XYD_Watch\objects\app_handler.o

?????文件?????289346??2019-04-15?11:12??XYD_Watch\objects\app_task.crf

?????文件???????1975??2019-04-15?11:12??XYD_Watch\objects\app_task.d

?????文件?????302752??2019-04-15?11:12??XYD_Watch\objects\app_task.o

?????文件?????277395??2019-04-15?11:12??XYD_Watch\objects\battery.crf

?????文件???????1179??2019-04-15?11:12??XYD_Watch\objects\battery.d

?????文件?????290672??2019-04-15?11:12??XYD_Watch\objects\battery.o

?????文件?????234753??2019-04-15?11:12??XYD_Watch\objects\bluetooth.crf

?????文件????????479??2019-04-15?11:12??XYD_Watch\objects\bluetooth.d

?????文件?????252856??2019-04-15?11:12??XYD_Watch\objects\bluetooth.o

?????文件?????235926??2019-04-15?11:12??XYD_Watch\objects\bp.crf

............此處省略243個文件信息