void USART1_IRQHandler(void)
{
   unsigned char res;
    
    if (USART_GetITStatus(USART1, USART_IT_RXNE) != RESET) //接收中断 有数据为 1 SET
    {
 USART_ClearITPendingBit(USART1,USART_IT_RXNE); //清除中断标志.   
                            
        res = (unsigned char)USART_ReceiveData(USART1);
          if(1 == res)
        {
           wr5024byte(0XFFFF);
        }
        if(2 == res)
        {
         wr5024byte(0X8000);
        }


      USART_SendData(USART1, USART_ReceiveData(USART1));        //接收到的数据重新发送到串口 
    }
}
 if(1 == res)
        {
           wr5024byte(0XFFFF);
        }
        if(2 == res)
if里的为什么不能执行啊