定时器1问题

GPIO_InitTypeDef GPIO_InitStruct;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStucture;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA,ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1,ENABLE) ;
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_9 ;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_Out_PP;//PA9为浮空输入模式
GPIO_Init(GPIOA,&GPIO_InitStruct);
TIM_TimeBaseStucture.TIM_Prescaler = 0;
TIM_TimeBaseStucture.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStucture.TIM_Period = 0xffff;
TIM_TimeBaseStucture.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseStucture.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM1,&TIM_TimeBaseStucture);
TIM_TIxExternalClockConfig(TIM1,TIM_TIxExternalCLK1Source_TI2 ,TIM_ICPolarity_Rising,0);
TIM_SetCounter(TIM1,2);
TIM_Cmd(TIM1,ENABLE);
这是我写的定时器程序 ，为什么不好使能 呢？