标签：stm32f407
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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STM32F407VG (四)时钟配置
标签：stm32f407
原文地址：http://blog.csdn.net/hitzjm/article/details/46695055
