我用外部中断上升沿触发检测片外AD是否转换完成，片外busy引脚长时间处于高电平，AD转换时BUSY先拉低，持续4us，再拉高，我用EXIT2检测上升沿，示波器可以抓到，但芯片没有检测到，一直没有进入中断。是不是4us时间太短的缘故？
我的配置如下：
static  void NVIC1_Configuration(void)
{
NVIC_InitTypeDef NVIC_InitStructure;

/* Configure the NVIC Preemption Priority Bits */  
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_0);

NVIC_InitStructure.NVIC_IRQChannel = EXTI2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
}

void Exti_Config(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
EXTI_InitTypeDef EXTI_InitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD,ENABLE);

SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOD, EXTI_PinSource2);

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_UP;
GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_2;

GPIO_Init(GPIOD, &GPIO_InitStructure);

EXTI_InitStructure.EXTI_Line=EXTI_Line2;
EXTI_InitStructure.EXTI_Mode=EXTI_Mode_Interrupt;
EXTI_InitStructure.EXTI_Trigger=EXTI_Trigger_Falling;
EXTI_InitStructure.EXTI_LineCmd=ENABLE;

EXTI_Init(&EXTI_InitStructure);

NVIC1_Configuration();
}