STM32 定时器问题

只看该作者 · 2012-4-27 13:59

如下配置定时器3通道3输出pwm, 定时可以正常输出，但如果改变ARR 的值，定时器为何停止工作，且无法再次使能
void TIM3_Initial(void)
{

TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_OCInitTypeDef  TIM_OCInitStructure;
  /* Time Base configuration */
  TIM_TimeBaseStructure.TIM_Prescaler = 0x08;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseStructure.TIM_Period = 31999;  //TIMx->ARR
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
  TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

  /* Enables the TIM3 Preload on ARR Register */
TIM_ARRPreloadConfig(TIM3, ENABLE);

  /* Channel 3Configuration in PWM mode */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Disable;
  TIM_OCInitStructure.TIM_Pulse = 16000;  //TIMx->CCR1
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low; //TIM_OCPolarity_Low
  TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset;
TIM_OC3Init(TIM3, &TIM_OCInitStructure);

  /* Enables the TIM3 Prelaod on CC3 Register */
  TIM_OC3PreloadConfig(TIM3, TIM_OCPreload_Enable);