程序这里                                             我把TIM3初始化给屏蔽了void TIM3_Int_Init(u16 arr,u16 psc)，还是是能跟不屏蔽TIM3初始化一样的效果，故这个TIM3初始化有什么用？

#include "pwm.h"
#include "led.h"
#include "usart.h"




//void TIM3_Int_Init(u16 arr,u16 psc)
//{
//   
//                TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
//          NVIC_InitTypeDef NVIC_InitStructure;
//               
//        //RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); //ê±Öóê1Äü
//  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);
//               
//        TIM_TimeBaseStructure.TIM_Period = arr;    //éèÖÃÔúÏÂò»¸ö¸üDÂê¼t×°èë»î¶ˉμÄ×Ô¶ˉÖØ×°ÔؼÄ′æÆ÷ÖüÆúμÄÖμ         ¼Æêyμ½5000Îa500ms
//        TIM_TimeBaseStructure.TIM_Prescaler =psc;  //éèÖÃóÃà′×÷ÎaTIMxê±ÖóÆμÂê3yêyμÄÔ¤·ÖÆμÖμ  10KhzμļÆêyÆμÂê  
//        TIM_TimeBaseStructure.TIM_ClockDivision = 0; //éèÖÃê±Öó·Ö¸î:TDTS = Tck_tim
//        TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  //TIMÏòéϼÆêyÄ￡ê½
//        TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); //¸ù¾YTIM_TimeBaseInitStructÖDÖ¸¶¨μÄ2Îêy3õê¼»ˉTIMxμÄê±¼ä»ùêyμ￥λ
//
//        TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE ); //ê1ÄüÖ¸¶¨μÄTIM3ÖD¶Ï,ÔêDí¸üDÂÖD¶Ï

//        NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;  //TIM3ÖD¶Ï
//        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;  //ÏèÕ¼óÅÏ輶0¼¶
//        NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;  //′óóÅÏ輶3¼¶
//        NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQí¨μà±»ê1Äü
//        NVIC_Init(&NVIC_InitStructure);  //¸ù¾YNVIC_InitStructÖDÖ¸¶¨μÄ2Îêy3õê¼»ˉíaéèNVIC¼Ä′æÆ÷

//        TIM_Cmd(TIM3, ENABLE);  //ê1ÄüTIMxíaéè
//                                                         
//}
////¶¨ê±Æ÷3ÖD¶Ï·tÎñ3ìDò
//void TIM3_IRQHandler(void)   //TIM3ÖD¶Ï
//{
//        if (TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET) //¼ì2éÖ¸¶¨μÄTIMÖD¶Ï·￠éúóë·ñ:TIM ÖD¶ÏÔ′
//                {
//                        TIM_ClearITPendingBit(TIM3, TIM_IT_Update  );  //Çå3yTIMxμÄÖD¶Ï′y′|àíλ:TIM ÖD¶ÏÔ′
//                        LED1=!LED1;
//                }
//}


//TIM3  pwm初始化
void TIM3_PWM_Init(u16 arr,u16 psc)
{  
        GPIO_InitTypeDef GPIO_InitStructure;
        TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
        TIM_OCInitTypeDef  TIM_OCInitStructure;
       

        RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);        //ê1Äü¶¨ê±Æ÷3ê±Öó
        RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB  | RCC_APB2Periph_AFIO, ENABLE);  //ê1ÄüGPIOíaéèoíAFIO¸′óÃ1|ÄüÄ￡¿éê±Öó
       
        GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3, ENABLE); //Timer32¿·ÖÖØó3éä  TIM3_CH2->B5   

   //éèÖøÃòy½ÅÎa¸′óÃêä3ö1|Äü,êä3öTIM3 CH2μ&#196WMÂö3å2¨DΠ       GPIOB.5
        GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5; //TIM_CH2
        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  //¸′óÃíÆíìêä3ö
        GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
        GPIO_Init(GPIOB, &GPIO_InitStructure);//3õê¼»ˉGPIO

   //3õê¼»ˉTIM3
        TIM_TimeBaseStructure.TIM_Period = arr; //éèÖÃÔúÏÂò»¸ö¸üDÂê¼t×°èë»î¶ˉμÄ×Ô¶ˉÖØ×°ÔؼÄ′æÆ÷ÖüÆúμÄÖμ
        TIM_TimeBaseStructure.TIM_Prescaler =psc; //éèÖÃóÃà′×÷ÎaTIMxê±ÖóÆμÂê3yêyμÄÔ¤·ÖÆμÖμ
        TIM_TimeBaseStructure.TIM_ClockDivision = 0; //éèÖÃê±Öó·Ö¸î:TDTS = Tck_tim
        TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  //TIMÏòéϼÆêyÄ￡ê½
        TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); //¸ù¾YTIM_TimeBaseInitStructÖDÖ¸¶¨μÄ2Îêy3õê¼»ˉTIMxμÄê±¼ä»ùêyμ￥λ
       
        //3õê¼»ˉTIM3 Channel2 PWMÄ￡ê½         
        TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2; //Ñ¡Ôñ¶¨ê±Æ÷Ä￡ê½:TIMÂö3å¿í¶èμ÷ÖÆÄ￡ê½2
        TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //±è½Ïêä3öê1Äü
        TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; //êä3ö¼«DÔ:TIMêä3ö±è½Ï¼«DÔ¸ß
        TIM_OC2Init(TIM3, &TIM_OCInitStructure);  //¸ù¾YTÖ¸¶¨μÄ2Îêy3õê¼»ˉíaéèTIM3 OC2

        TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);  //ê1ÄüTIM3ÔúCCR2éÏμÄԤװÔؼÄ′æÆ÷

        TIM_Cmd(TIM3, ENABLE);  //ê1ÄüTIM3
       

}


还有这个主程序，//NVIC_Configuration();         //uart_init(9600);          这两句串口跟向量中断设置跟pwm输出有什么联系，我屏蔽了也不影响结果啊。


int main(void)
{               
        u16 led0pwmval=0;
        u8 dir=1;       
        delay_init();                     //Ñóê±oˉêy3õê¼»ˉ          
        //NVIC_Configuration();          //éèÖÃNVICÖD¶Ï·Ö×é2:2λÇàÕ¼óÅÏ輶￡¬2λÏìó|óÅÏ輶
        //uart_init(9600);         //′®¿ú3õê¼»ˉÎa9600
        LED_Init();                             //LED¶Ë¿ú3õê¼»ˉ
        TIM3_PWM_Init(899,0);         //2»·ÖÆμ¡￡PWMÆμÂê=72000/900=8Khz

        while(1)
        {}