Question

我正在使用stm32f103的定时器2（TIM2）来设置时钟中断，并在定时器的中断例程中复位输出引脚（PA1）。所以当我设置定时器的参数如下：

TIM_BaseInitStructure.TIM_Period=36;                                                    
TIM_BaseInitStructure.TIM_Prescaler = 0;

我刚刚在逻辑分析仪中看到了输出引脚的478 Khz时钟频率，而不是1Mhz。当我减少TIM_Period时，时钟频率没有变化，大约是500 Khz。有什么问题？

int main(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    SystemInit();           
    Init_NVIC();                

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB | RCC_APB2Periph_GPIOE | RCC_APB2Periph_AFIO, ENABLE);

    /*PA1 CLK TIM2_CH2*/
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1 ;               
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;           
    GPIO_Init(GPIOA ,&GPIO_InitStructure);

    /*PB0 CK*/
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 ;               
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;           
    GPIO_Init(GPIOB ,&GPIO_InitStructure);
    Init_TIMER();               
    while(1)
    {  

    }     
}
void Init_NVIC(void)
{
    NVIC_InitTypeDef    NVIC_InitStructure;

    #ifdef  VECT_TAB_RAM                                    

      NVIC_SetVectorTable(NVIC_VectTab_RAM, 0x0);           
    #else  

      NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x0);           
    #endif
    NVIC_PriorityGroupConfig(NVIC_PriorityGroup_0);     

    NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;         
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;   

    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;      
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;         
    NVIC_Init(&NVIC_InitStructure);                         
}
void Init_TIMER(void)
{
    TIM_TimeBaseInitTypeDef  TIM_BaseInitStructure;         
    TIM_OCInitTypeDef  TIM_OCInitStructure;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);    

    TIM_DeInit( TIM2);                                      

    TIM_InternalClockConfig(TIM2);                      

    TIM_BaseInitStructure.TIM_Period = 18;                                                                  


    TIM_BaseInitStructure.TIM_Prescaler = 0;                

    TIM_BaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1; 
    TIM_BaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;   


    TIM_TimeBaseInit(TIM2, &TIM_BaseInitStructure);         

    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse = 18;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OC2Init(TIM2, &TIM_OCInitStructure);

    TIM_OC2PreloadConfig(TIM2, TIM_OCPreload_Disable);

    TIM_ClearFlag(TIM2, TIM_IT_CC2);                     

    TIM_ITConfig(TIM2,TIM_IT_CC2, ENABLE);                      
    TIM_Cmd(TIM2, ENABLE);

}

void TIM2_IRQHandler(void)
{
    CK=~CK;

    if (TIM_GetITStatus(TIM2, TIM_IT_CC2) != RESET)         
    {                                      
        TIM_ClearITPendingBit(TIM2, TIM_IT_CC2);                    
    }
}

timer2（TIM2）STM32是否存在频率限制

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