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The output signals at the maximum frequency.

Question asked by k.serg on Dec 21, 2011
Latest reply on Dec 21, 2011 by Clive One
How can I synchronize the timer output with a maximum frequency PLL,
ie 168 MHz.  In my example I set the timer to slow generate an interrupt,
which run fast timer for generating a single pulse duration of 6 ns,
but I have a jitter of 10 ns.
Example my codes:
1)
  /* Time base configuration TIM9 (fast)*/
  TIM_TimeBaseStructure.TIM_Period = 100;
  TIM_TimeBaseStructure.TIM_Prescaler = 0; // max freq. (168 MHz)
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
 
  TIM_TimeBaseInit(TIM9, &TIM_TimeBaseStructure);
 
  /* TIM9 PWM2 Mode configuration: Channel1 */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 100;//get pulse ~6ns
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
 
  TIM_OC1Init(TIM9, &TIM_OCInitStructure);
 
  /* One Pulse Mode selection */
  TIM_SelectOnePulseMode(TIM9, TIM_OPMode_Single);
 
  /* Time base configuration TIM3 (slow) */
 
  TIM_TimeBaseStructure.TIM_Period = 1000;
  TIM_TimeBaseStructure.TIM_Prescaler = 8;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
 
  TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
 
  /* PWM1 Mode configuration: Channel4 */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 0; // pulse for control
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
 
  TIM_OC4Init(TIM3, &TIM_OCInitStructure);
 
  //TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Enable);
 
  TIM_ARRPreloadConfig(TIM3, ENABLE);
  /* TIM Interrupts enable */
  TIM_ITConfig(TIM3, TIM_IT_CC4 , ENABLE);
 
  /* TIM3 enable counter */
  TIM_Cmd(TIM3, ENABLE);
 
 2) config output pins
   /* TIM3 clock enable */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
    /* Enable peripheral clocks */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC | RCC_AHB1Periph_GPIOE, ENABLE);
  /* TIM9 clock enable */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM9, ENABLE);
  /* TIM3_CH4 pin (PC.09) configuration */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_Init(GPIOC, &GPIO_InitStructure);
 
  /* TIM9_CH1 pin (PE.05) configuration */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_Init(GPIOE, &GPIO_InitStructure);
 
3) interrupt config
  /* Enable the TIM3 gloabal Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
 
4) interrupt routine
void TIM3_IRQHandler(void)
{
  if (TIM3->SR & TIM_IT_CC4) //
  {
    /* Clear the IT pending Bit */
    TIM3->SR &= ~TIM_IT_CC4;
    TIM9->CR1 |= TIM_CR1_CEN; // start new pulse
  }
}
 
TIM9_CH1 (PE.05) output should be synchronized with TIM3_CH4 (PC.09) oputput, but it don't.
How to fix this trouble?

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