修改了一下英倍特板例程，做了个跑马灯小实验，系统时钟用8M*9=72M，每个灯延时常数为0x0B71B00（十进制数12M），用示波器测出刚好是延时1S，说明时钟是12M，可是下面的程序中系统时钟是72M的，是我的理解有误吗？希望高手赐教。
#include "stm32f10x_lib.h"
GPIO_InitTypeDef GPIO_InitStructure;
ErrorStatus HSEStartUpStatus;
/* Private function prototypes -----------------------------------------------*/
void RCC_Configuration(void);
//void NVIC_Configuration(void);
void Delay(vu32 nCount);
int main(void)
{
#ifdef DEBUG
debug();
#endif
/* Configure the system clocks */
RCC_Configuration();
/* NVIC Configuration */
// NVIC_Configuration();
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOC, &GPIO_InitStructure);
while (1)
{ GPIO_SetBits(GPIOC,GPIO_Pin_0);
GPIO_ResetBits(GPIOC,GPIO_Pin_3);
Delay(0x0B71B00); //Delay 1S ,12MHZ？
GPIO_SetBits(GPIOC,GPIO_Pin_1);
GPIO_ResetBits(GPIOC,GPIO_Pin_0);
Delay(0x0B71B00);
GPIO_SetBits(GPIOC,GPIO_Pin_2);
GPIO_ResetBits(GPIOC,GPIO_Pin_1);
Delay(0x0B71B00);
GPIO_SetBits(GPIOC,GPIO_Pin_3);
GPIO_ResetBits(GPIOC,GPIO_Pin_2);
Delay(0x0B71B00);
}
}
void RCC_Configuration(void)
{
/* RCC system reset(for debug purpose) */
RCC_DeInit();
/* Enable HSE */
RCC_HSEConfig(RCC_HSE_ON);
/* Wait till HSE is ready */
HSEStartUpStatus = RCC_WaitForHSEStartUp();
if(HSEStartUpStatus == SUCCESS)
{
/* HCLK = SYSCLK */
RCC_HCLKConfig(RCC_SYSCLK_Div1);
/* PCLK2 = HCLK */
RCC_PCLK2Config(RCC_HCLK_Div1);
/* PCLK1 = HCLK/2 */
RCC_PCLK1Config(RCC_HCLK_Div2);
/* Flash 2 wait state */
FLASH_SetLatency(FLASH_Latency_2);
/* Enable Prefetch Buffer */
FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
/* PLLCLK = 8MHz * 9 = 72 MHz */
RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);
/* Enable PLL */
RCC_PLLCmd(ENABLE);
/* Wait till PLL is ready */
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET)
{
}
/* Select PLL as system clock source */
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
/* Wait till PLL is used as system clock source */
while(RCC_GetSYSCLKSource() != 0x08)
{
}
}
/* Enable GPIOA, GPIOB and AFIO clocks */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB |
RCC_APB2Periph_GPIOC| RCC_APB2Periph_AFIO, ENABLE);
}
void Delay(vu32 nCount)
{
for(; nCount != 0; nCount--);
} |
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