/**
??******************************************************************************
??*?@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(shí)間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2019-03-21?16:16??DebugConfig\
?????文件????????2084??2015-10-27?12:06??DebugConfig\Target_1_STM32F407ZG.dbgconf
?????目錄???????????0??2019-03-21?16:16??Listings\
?????文件??????110488??2019-03-22?09:27??Listings\STM32F4_Project.map
?????文件???????77631??2019-03-22?09:27??Listings\startup_stm32f40_41xxx.lst
?????目錄???????????0??2019-03-22?09:27??objects\
?????文件??????375796??2019-03-22?09:27??objects\STM32F4_Project.axf
?????文件????????3445??2019-03-22?09:27??objects\STM32F4_Project.build_log.htm
?????文件????????1837??2017-10-30?15:15??objects\STM32F4_Project.fed
?????文件???????90816??2019-03-22?09:27??objects\STM32F4_Project.hex
?????文件??????104746??2019-03-22?09:27??objects\STM32F4_Project.htm
?????文件?????????587??2017-10-30?15:15??objects\STM32F4_Project.l2p
?????文件?????????737??2019-03-22?09:27??objects\STM32F4_Project.lnp
?????文件???????16373??2019-03-22?09:27??objects\STM32F4_Project_Target?1.dep
?????文件??????265027??2019-03-22?09:27??objects\at24c02.crf
?????文件?????????570??2019-03-22?09:27??objects\at24c02.d
?????文件??????285528??2019-03-22?09:27??objects\at24c02.o
?????文件??????273957??2019-03-22?09:27??objects\calculator.crf
?????文件?????????680??2019-03-22?09:27??objects\calculator.d
?????文件??????285276??2019-03-22?09:27??objects\calculator.o
?????文件?????????362??2017-10-30?15:15??objects\delay._2i
?????文件??????262373??2019-03-22?09:27??objects\delay.crf
?????文件?????????426??2019-03-22?09:27??objects\delay.d
?????文件??????280044??2019-03-22?09:27??objects\delay.o
?????文件??????266112??2019-03-22?09:27??objects\iic.crf
?????文件?????????479??2019-03-22?09:27??objects\iic.d
?????文件??????284556??2019-03-22?09:27??objects\iic.o
?????文件??????263192??2019-03-22?09:27??objects\io_bit.crf
?????文件?????????437??2019-03-22?09:27??objects\io_bit.d
?????文件??????280280??2019-03-22?09:27??objects\io_bit.o
?????文件?????????354??2017-10-30?15:15??objects\key._2i
............此處省略124個(gè)文件信息