void TIM3_Configuration(void)//1MS

 {

     TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;

         TIM_DeInit(TIM3);//开一下时钟再关闭

         /* 设置TIM2CLK 为 72MHZ */

     RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3 , ENABLE);

     /* 自动重装载寄存器周期的值(计数值) */

     TIM_TimeBaseStructure.TIM_Period=-;

     /* 累计 TIM_Period个频率后产生一个更新或者中断 */

     TIM_TimeBaseStructure.TIM_Prescaler= ;

         TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;/* 时钟预分频数为72 */

     TIM_TimeBaseStructure.TIM_CounterMode=TIM_CounterMode_Up;

     TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

     TIM_ClearFlag(TIM3, TIM_FLAG_Update);

         TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE);

         TIM_ARRPreloadConfig(TIM3, ENABLE);

     TIM_Cmd(TIM3, ENABLE);                                                                        

 }

void TIM3_NVIC_Configuration(void)

{

    NVIC_InitTypeDef NVIC_InitStructure; 

    NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);

    NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;

    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = ;

    NVIC_InitStructure.NVIC_IRQChannelSubPriority = ;

    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

    NVIC_Init(&NVIC_InitStructure);

}