STM32定时器配置

主机环境：Windows XP

开发环境：Keil4

目标板：STM32F030C8T6

库函数版本:STM32F0_StdPeriph_LibV1.3.0

在编辑定时器代码时，发现刚配置完定时器即使没有使能定时器也会进入一次定时器中断，代码如下

	/* TIM3 clock enable*/
	RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);
	
	/* Enable the TIM3 gloabal Interrupt */
	NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
	NVIC_InitStructure.NVIC_IRQChannelPriority = 0x02;
	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
	NVIC_Init(&NVIC_InitStructure);
	
	TIM_TimeBaseStructure.TIM_Prescaler = 1535;//1536分频48MHz/1536=31.25K
	TIM_TimeBaseStructure.TIM_ClockDivision = 0;
	TIM_TimeBaseStructure.TIM_Period = 0xF424;//2s
	TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;//向上计数
	
	TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
	
	TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE);//开启更新中断
	
	TIM_Cmd(TIM3,DISABLE);

后来才发现原来在TIM_TimeBaseInit()函数中会产生一次更新事件，如下

void TIM_TimeBaseInit(TIM_TypeDef* TIMx, TIM_TimeBaseInitTypeDef* TIM_TimeBaseInitStruct)
{
  uint16_t tmpcr1 = 0;

  /* Check the parameters */
  assert_param(IS_TIM_ALL_PERIPH(TIMx)); 
  assert_param(IS_TIM_COUNTER_MODE(TIM_TimeBaseInitStruct->TIM_CounterMode));
  assert_param(IS_TIM_CKD_DIV(TIM_TimeBaseInitStruct->TIM_ClockDivision));

  tmpcr1 = TIMx->CR1;  

  if((TIMx == TIM1) || (TIMx == TIM2) || (TIMx == TIM3))
  {
    /* Select the Counter Mode */
    tmpcr1 &= (uint16_t)(~((uint16_t)(TIM_CR1_DIR | TIM_CR1_CMS)));
    tmpcr1 |= (uint32_t)TIM_TimeBaseInitStruct->TIM_CounterMode;
  }
 
  if(TIMx != TIM6)
  {
    /* Set the clock division */
    tmpcr1 &= (uint16_t)(~((uint16_t)TIM_CR1_CKD));
    tmpcr1 |= (uint32_t)TIM_TimeBaseInitStruct->TIM_ClockDivision;
  }

  TIMx->CR1 = tmpcr1;

  /* Set the Autoreload value */
  TIMx->ARR = TIM_TimeBaseInitStruct->TIM_Period ;
 
  /* Set the Prescaler value */
  TIMx->PSC = TIM_TimeBaseInitStruct->TIM_Prescaler;
    
  if ((TIMx == TIM1) || (TIMx == TIM15)|| (TIMx == TIM16) || (TIMx == TIM17))  
  {
    /* Set the Repetition Counter value */
    TIMx->RCR = TIM_TimeBaseInitStruct->TIM_RepetitionCounter;
  }

  /* Generate an update event to reload the Prescaler and the Repetition counter
     values immediately */
  TIMx->EGR = TIM_PSCReloadMode_Immediate;           
}

会加载重计数器，因此在刚配置完定时器后需要手动清除一次标识，如下

	TIM3 clock enable*/
	RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);
	
	/* Enable the TIM3 gloabal Interrupt */
	NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
	NVIC_InitStructure.NVIC_IRQChannelPriority = 0x02;
	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
	NVIC_Init(&NVIC_InitStructure);
	
	TIM_TimeBaseStructure.TIM_Prescaler = 1535;//1536分频48MHz/1536=31.25K
	TIM_TimeBaseStructure.TIM_ClockDivision = 0;
	TIM_TimeBaseStructure.TIM_Period = 0xF424;//2s
	TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;//向上计数
	
	TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
	
	while(TIM_GetFlagStatus(TIM3, TIM_IT_Update) == RESET);//等待软件更新数据
	TIM_ClearITPendingBit(TIM3,TIM_IT_Update);//清中断
	
	TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE);//开启更新中断
	
	TIM_Cmd(TIM3,DISABLE);

如此这般就不会出现刚配置完定时器就进入中断的情况了，虽然影响也不大。。。