TIM3使用外部高速晶振，为何得不到我预期的时间

战舰水手

[mw_shl_code=c,true]int main(void) { RCC_Configuration(); delay_init(); //延时函数初始化 NVIC_Configuration(); //设置NVIC中断分组2:2位抢占优先级，2位响应优先级 uart_init(9600); //串口初始化为9600 LED_Init(); //LED端口初始化 TIM3_Int_Init(4999,800);//10Khz的计数频率，计数到5000为500ms while(1) { LED0=!LED0; delay_ms(100); } [/mw_shl_code]

[mw_shl_code=c,true]void TIM3_Int_Init(u16 arr,u16 psc) { TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure; NVIC_InitTypeDef NVIC_InitStructure; RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); //时钟使能 //定时器TIM3初始化 TIM_TimeBaseStructure.TIM_Period = arr; //设置在下一个更新事件装入活动的自动重装载寄存器周期的值 TIM_TimeBaseStructure.TIM_Prescaler =psc; //设置用来作为TIMx时钟频率除数的预分频值 TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //设置时钟分割:TDTS = Tck_tim TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //TIM向上计数模式 TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); //根据指定的参数初始化TIMx的时间基数单位 TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE ); //使能指定的TIM3中断,允许更新中断 //中断优先级NVIC设置 NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn; //TIM3中断 NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; //先占优先级0级 NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3; //从优先级3级 NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ通道被使能 NVIC_Init(&NVIC_InitStructure); //初始化NVIC寄存器 TIM_Cmd(TIM3, ENABLE); //使能TIMx } //定时器3中断服务程序 void TIM3_IRQHandler(void) //TIM3中断 { if (TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET) //检查TIM3更新中断发生与否 { TIM_ClearITPendingBit(TIM3, TIM_IT_Update ); //清除TIMx更新中断标志 LED1=!LED1; } } [/mw_shl_code]

[mw_shl_code=c,true]void RCC_Configuration(void) { ErrorStatus HSEStartUpStatus; RCC_DeInit(); RCC_HSEConfig(RCC_HSE_ON); HSEStartUpStatus=RCC_WaitForHSEStartUp(); if(HSEStartUpStatus==SUCCESS) { RCC_HCLKConfig(RCC_SYSCLK_Div1); RCC_PCLK2Config(RCC_HCLK_Div1); RCC_PCLK1Config(RCC_HCLK_Div1);// FLASH_SetLatency(FLASH_Latency_2); FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable); RCC_PLLConfig(RCC_PLLSource_HSE_Div1,RCC_PLLMul_9); RCC_PLLCmd(ENABLE); while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY)==RESET); RCC_SYSCLKConfig(RCC_SYSCLKSource_HSE); while(RCC_GetSYSCLKSource()!=0x04); } }[/mw_shl_code]

tim3的时钟是AHB1，因为AHB1是由HSE来，所以TIM3的时钟频率是8MHZ， [mw_shl_code=c,true]TIM3_Int_Init(4999,800);就是500ms更新中断一次，但我通过观察DS1闪烁发现次大概是1s闪烁一次，非常郁闷，哪里不对？[/mw_shl_code]

正点原子

仿真看下系统时钟就知道了。

lycreturn

500ms高  500ms低   一个周期就是1s了  哪里不对？