/**
??******************************************************************************
??*?@file????system_stm32f4xx.c
??*?@author??MCD?Application?Team
??*?@version?V1.8.0
??*?@date????04-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????時間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2018-04-14?22:59??SmartHome\CMSIS\
?????文件??????114403??2016-11-05?01:33??SmartHome\CMSIS\core_cm4.h
?????文件???????18323??2016-11-05?01:33??SmartHome\CMSIS\core_cmFunc.h
?????文件???????27908??2016-11-05?01:33??SmartHome\CMSIS\core_cmInstr.h
?????文件???????22947??2016-11-05?01:33??SmartHome\CMSIS\core_cmSimd.h
?????目錄???????????0??2018-04-14?22:59??SmartHome\CMSIS\startup\
?????文件???????29607??2018-03-30?19:27??SmartHome\CMSIS\startup\startup_stm32f40_41xxx.s
?????文件??????940126??2018-03-15?10:37??SmartHome\CMSIS\stm32f4xx.h
?????文件???????61019??2018-03-15?10:39??SmartHome\CMSIS\system_stm32f4xx.c
?????文件????????2235??2016-11-07?23:03??SmartHome\CMSIS\system_stm32f4xx.h
?????目錄???????????0??2018-04-14?22:59??SmartHome\Driver\
?????目錄???????????0??2018-04-14?22:59??SmartHome\Driver\inc\
?????文件?????????405??2018-04-02?18:01??SmartHome\Driver\inc\adc.h
?????文件?????????239??2018-03-16?15:29??SmartHome\Driver\inc\beep.h
?????文件?????????259??2018-03-17?11:36??SmartHome\Driver\inc\delay.h
?????文件?????????986??2018-04-04?17:59??SmartHome\Driver\inc\dht11.h
?????文件?????????112??2018-04-04?17:58??SmartHome\Driver\inc\flame.h
?????文件?????????330??2018-04-04?16:27??SmartHome\Driver\inc\hc-sr04.h
?????文件?????????759??2018-03-16?15:29??SmartHome\Driver\inc\key.h
?????文件????????1064??2018-03-28?11:33??SmartHome\Driver\inc\lan8720.h
?????文件?????????645??2018-03-21?15:26??SmartHome\Driver\inc\led.h
?????文件????????2832??2016-04-15?21:59??SmartHome\Driver\inc\malloc.h
?????文件?????????296??2018-03-21?18:02??SmartHome\Driver\inc\rs485.h
?????文件?????????168??2018-04-04?17:35??SmartHome\Driver\inc\sr501.h
?????文件?????????849??2016-04-15?21:59??SmartHome\Driver\inc\sram.h
?????文件????????3442??2015-04-18?11:06??SmartHome\Driver\inc\sys.h
?????文件?????????367??2018-03-30?20:50??SmartHome\Driver\inc\usart.h
?????目錄???????????0??2018-04-14?22:59??SmartHome\Driver\src\
?????文件????????6793??2018-04-02?18:01??SmartHome\Driver\src\adc.c
?????文件?????????730??2018-03-29?16:39??SmartHome\Driver\src\beep.c
?????文件????????1293??2018-03-29?17:11??SmartHome\Driver\src\delay.c
............此處省略433個文件信息