ucos任务开启定时器就不准？

只看该作者 · 2013-7-9 17:20

void DRV_Tim3Init(void)
{
NVIC_InitTypeDef NVIC_InitStructure;
TIM_DeInit(TIM3);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
TIM3->PSC =0;
TIM3->ARR = (unsigned int)(12000/16);//定时16K//系统时钟120M
TIM3->DIER|=1<<0;    //允许更新中断
NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQChannel;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
BSP_IntVectSet(BSP_INT_ID_TIM3, DRV_Tim3Irq);
BSP_IntEn(BSP_INT_ID_TIM3);

}
void DRV_Tim3Irq(void)
{
  unsigned char data;
  static uint8 flag=0;
if(flag)
  {
SetRLED();
flag=0;
  }
  else
  {
   ClrRLED();
   flag=1;
  }
  TIM3->SR&=~(1<<0);//清除中断标志位

}

UcOs开四个任务其中一个任务是20ms执行一次，另三个挂起状态，为什么中断中红灯亮灭波形频率小于16K（大约15K）有些大于16K，定时器会变得不准？