/**
??******************************************************************************
??*?@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）???????????????????????????????|?168000000
??*-------------------------

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2017-05-08?21:46??DRVBD_TestSource（2017.5.08）\
?????目錄???????????0??2017-05-08?21:10??DRVBD_TestSource（2017.5.08）\CMSIS\
?????文件??????107370??2017-05-08?21:09??DRVBD_TestSource（2017.5.08）\CMSIS\core_cm4.h
?????文件???????22062??2017-05-08?21:09??DRVBD_TestSource（2017.5.08）\CMSIS\core_cm4_simd.h
?????文件???????16510??2017-05-08?21:09??DRVBD_TestSource（2017.5.08）\CMSIS\core_cmFunc.h
?????文件???????19825??2017-05-08?21:09??DRVBD_TestSource（2017.5.08）\CMSIS\core_cmInstr.h
?????文件???????29171??2017-05-08?21:09??DRVBD_TestSource（2017.5.08）\CMSIS\startup_stm32f40_41xxx.s
?????文件??????695938??2017-05-08?21:10??DRVBD_TestSource（2017.5.08）\CMSIS\stm32f4xx.h
?????文件???????46664??2017-05-08?21:09??DRVBD_TestSource（2017.5.08）\CMSIS\system_stm32f4xx.c
?????文件????????2148??2017-05-08?21:09??DRVBD_TestSource（2017.5.08）\CMSIS\system_stm32f4xx.h
?????目錄???????????0??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\
?????目錄???????????0??2017-05-08?21:47??DRVBD_TestSource（2017.5.08）\FWlib\inc\
?????文件????????6746??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\misc.h
?????文件???????32224??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_adc.h
?????文件???????26674??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_can.h
?????文件????????2333??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_crc.h
?????文件???????14097??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_cryp.h
?????文件???????14642??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_dac.h
?????文件????????4187??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_dbgmcu.h
?????文件???????12665??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_dcmi.h
?????文件???????28273??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_dma.h
?????文件???????19217??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_dma2d.h
?????文件????????7829??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_exti.h
?????文件???????23979??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_flash.h
?????文件????????3172??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_flash_ramfunc.h
?????文件???????43781??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_fmc.h
?????文件???????26506??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_fsmc.h
?????文件???????23046??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_gpio.h
?????文件????????9827??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_hash.h
?????文件???????31228??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_i2c.h
?????文件????????4192??2017-05-08?21:20??DRVBD_TestSource（2017.5.08）\FWlib\inc\stm32f4xx_iwdg.h
............此處省略268個文件信息