STM32F407VG (四)时钟配置

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1.STM32 F407VG 的starup_stm32f40_41xxx.s的如下位置调用 IMPORT SystemInit，之后调用main函数，所以

进入main函数时候就已经自动完成有关时钟配置了。

2.在SystemInit函数里面完成时钟配置，配上图和如下注释就不需要多解释了，一目了然。

下面注释截取自system_stm32f4xx.c

*=============================================================================

* Supported STM32F40xxx/41xxx devices

*-----------------------------------------------------------------------------

* System Clock source | PLL (HSE)

*-----------------------------------------------------------------------------

* SYSCLK(Hz) | 168000000

*-----------------------------------------------------------------------------

* HCLK(Hz) | 168000000

*-----------------------------------------------------------------------------

* AHB Prescaler | 1

*-----------------------------------------------------------------------------

* APB1 Prescaler | 4

*-----------------------------------------------------------------------------

* APB2 Prescaler | 2

*-----------------------------------------------------------------------------

* HSE Frequency(Hz) | 25000000

*-----------------------------------------------------------------------------

* PLL_M | 25

*-----------------------------------------------------------------------------

* PLL_N | 336

*-----------------------------------------------------------------------------

* PLL_P | 2

*-----------------------------------------------------------------------------

* PLL_Q | 7

*-----------------------------------------------------------------------------

* PLLI2S_N | NA

*-----------------------------------------------------------------------------

* PLLI2S_R | NA

*-----------------------------------------------------------------------------

* I2S input clock | NA

*-----------------------------------------------------------------------------

* VDD(V) | 3.3

*-----------------------------------------------------------------------------

* Main regulator output voltage | Scale1 mode

*-----------------------------------------------------------------------------

* Flash Latency(WS) | 5

*-----------------------------------------------------------------------------

* Prefetch Buffer | ON

*-----------------------------------------------------------------------------

* Instruction cache | ON

*-----------------------------------------------------------------------------

* Data cache | ON

*-----------------------------------------------------------------------------

* Require 48MHz for USB OTG FS, | Disabled

* SDIO and RNG clock |

*-----------------------------------------------------------------------------

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