（1）内部时钟（CK_INT）

（2）外部时钟模式1：外部输入脚（TIx）

（3）外部时钟模式2：外部触发输入（ETR）

（4）内部触发输入（ITRx）

时钟源（CK_INT）经预分频（PSC）后得到定时时钟（CK_CNT），每个定时时钟计数寄存器计数（可设向上/向下/中央对齐模式），计数寄存器计数至捕获比较寄存器（CCR），则产生CC中断；计数寄存器计数至预装载值（ARR），则产生UPDATE中断，并重装预载值。

举个例子：（以向上计数为例，每40us中断一次）

void TIM2_Configuration(void)
{
 TIM_TimeBaseInitTypeDef   TIM_TimeBaseStructure;
 TIM_OCInitTypeDef         TIM_OCInitStructure;
 
 RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE); // for 36MHz

 
 TIM_DeInit(TIM2);
 TIM_TimeBaseStructInit(&TIM_TimeBaseStructure); 
 TIM_TimeBaseStructure.TIM_Period = 1200;                // 预装初值
 TIM_TimeBaseStructure.TIM_Prescaler = 36-1;            // 预分频
 TIM_TimeBaseStructure.TIM_ClockDivision = 0x00;     // 时钟分频因子（用于ETR，TIX）
 TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;       // 向上计数
 TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;    // 重复计数
 TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

 /*-------------------*/
 TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Timing;
 TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
 TIM_OCInitStructure.TIM_Pulse = 40;                            //40us中断一次
 TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
 TIM_OC1Init(TIM2, &TIM_OCInitStructure);
 TIM_OC1PreloadConfig(TIM2, TIM_OCPreload_Disable);
 
 /*-------------------*/
 TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Timing;
 TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Disable;
 TIM_OCInitStructure.TIM_Pulse = 800;                        //PWM 800/1200
 TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
 TIM_OC2Init(TIM2, &TIM_OCInitStructure);
 TIM_OC2PreloadConfig(TIM2, TIM_OCPreload_Disable);
  
 /*-------------------*/
// TIM_SelectSlaveMode(TIM2, TIM_SlaveMode_Gated);
// TIM_SelectInputTrigger(TIM2, TIM_TS_ITR0);
 
 TIM_ARRPreloadConfig(TIM2, DISABLE);
 
 TIM_ITConfig(TIM2, TIM_IT_CC1|TIM_IT_CC2|TIM_IT_Update, ENABLE); 
 TIM_Cmd(TIM2, ENABLE); 
}

/*--------------中断程序-------------------*/
void TIM2_IRQHandler(void)
{

uint16_t capture = 0;

 if(TIM_GetITStatus(TIM2, TIM_IT_CC1) != RESET)

 {  

  if((timer_cnt1++)>49)

  {

   timer_cnt1 = 0;

   f_2ms = 1;   

  }
  

  TIM_ClearITPendingBit(TIM2, TIM_IT_CC1);

  capture = TIM_GetCapture1(TIM2);

  if(capture==1200)

      TIM_SetCompare1(TIM2, 40);

  else

      TIM_SetCompare1(TIM2, capture + 40);

    }  

 if(TIM_GetITStatus(TIM2, TIM_IT_CC2) != RESET)

 {

  GPIO_SetBits(P_LCDBK, LCDBK);

 }

 if(TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)

  GPIO_ResetBits(P_LCDBK, LCDBK);

 TIM2->SR = 0x00;
}