TIM1_DeInit();  
        TIM1_TimeBaseInit(16, TIM1_COUNTERMODE_UP, 999, 0x00);//250  
        TIM1_OC4Init(TIM1_OCMODE_PWM1, TIM1_OUTPUTSTATE_ENABLE, 499, TIM1_OCPOLARITY_LOW, TIM1_OCIDLESTATE_RESET);//50%占空比  
        TIM1_CCxCmd(TIM1_CHANNEL_4, ENABLE);  
        TIM1_OC4PreloadConfig(ENABLE);  
        TIM1_CtrlPWMOutputs(ENABLE);  
        TIM1_Cmd(ENABLE);



tim1配置如上图，为什么没有正常输出？
求大神帮帮忙