高人指点 UART不能中断

UART, 高人, 指点

我是新手麻烦高人指点啊现在是我连上串口以后跑马灯正常,按PC机的任意键都会使其停在某一位置,然后就没任何反应了,另外,上电后,PC机只是收到两个' * ' 并不是****UART IRQ TEST**** 程序如下:

#include "system.h"
#include "io.h"
#include "alt_types.h"
#include <stdio.h>
//#include "altera_avalon_jtag_uart_regs.h"
#include "sys/alt_irq.h"

unsigned char New_Command=0;
unsigned int data;
void UART_0_irq(void *context,alt_u32 interrupt)
{
    data=IORD(UART_0_BASE,0x00); //读取rxdata寄存器
    IOWR(UART_0_BASE,0x02,0x00);// 清除status寄存器
    New_Command=1;
}
int main (void)
{
    unsigned char led=0x02;
    unsigned char dir=0x00;
    volatile int i=0;
    printf("****UART IRQ TEST****\n");
    IOWR(UART_0_BASE,0x03,0x80); //设置control寄存器
    //IOWR(UART_0_BASE,0x00,0x00); //clear rxdata
    IOWR(UART_0_BASE,0x02,0x00);// 清除status寄存器
    if(alt_irq_register(UART_0_IRQ, NULL,UART_0_irq))
       printf("interrupt register FAIL! \n");
    while(1)
    {
      if (led & 0x11)
      {
        dir = (dir ^ 0x1);
      }
      if (dir)
      {
        led = led >> 1;
      }
      else
      {
        led = led << 1;
      }
      IOWR(LED_BASE,0x00,led);
      i = 0;
      while (i<20000)
        i++;
      if(New_Command==1)
      {
          printf("***Receive data***\n");
          New_Command=0;
          i=0;
          switch(data)
          {
              case 1:
                  IOWR(LED_BASE,0x00,21);
                  printf("****Do the first thing****\n");
                  while(i<900000)
                     i++;
                  i=0;
                  break;
              case 2:
                  IOWR(LED_BASE,0x00,10);
                  printf("****Do the second thing****\n");
                  while(i<900000)
                     i++;
                  i=0;
                  break;
              default: break;
          }
      }
    }
    return 0;
}