用单个595，编写程序成功。可是两个级联不知如何写入数据使LED灯逐个点亮。请指教，一片595的代码如下：  
#include <reg52.h>        //51芯片管脚定义头文件
#include <intrins.h>       //内部包含延时函数 _nop_();
#define uchar unsigned char
#define uint  unsigned int uchar code DAT[8]={0xfe,0xfc,0xf8,0xf0,0xe0,0xc0,0x80,0x00}; sbit  SDATA_595=P3^0;         //串行数据输入
sbit  SCLK_595 =P3^1;          //移位时钟脉冲
sbit  RCK_595  =P3^2;           //输出锁存器控制脉冲 uchar temp;             /********************************************************/
/*                                                                                                            */
/* 延时子程序                                                                                            */
/*                                                                                                            */
/********************************************************/ void delay(int ms)
{                          
   int k;
   while(ms--)
   {
     for(k=0; k<250; k++)
     {
      _nop_();
      _nop_();
      _nop_();
      _nop_();
     }
   }
} /********************************************************/
/*                                                                                                            */
/*将显示数据送入74HC595内部移位寄存器                                                   */
/*                                                                                                            */
/********************************************************/ void WR_595(void)
{
     uchar j;
      for (j=0;j<8;j++)
     {
      temp=temp<<1;
      SDATA_595=CY;
      SCLK_595=1;                     //上升沿发生移位
       _nop_();
       _nop_();
      SCLK_595=0;
     }       
} /********************************************************/
/*                                                                                                            */
/*将移位寄存器内的数据锁存到输出寄存器并显示                                             */
/*                                                                                                            */
/********************************************************/  void OUT_595(void)
{
    RCK_595=0;
    _nop_();
    _nop_();
    RCK_595=1;                       //上升沿将数据送到输出锁存器
    _nop_();
    _nop_();
    _nop_();
    RCK_595=0;
}   main()
{ 
   SCLK_595=0;
   RCK_595=1;
   
   while(1)            
    {
      uchar i;
      for (i=0; i<8; i++)
       {
        temp=DAT;         //取显示数据
        WR_595();
        OUT_595();
        delay(30);
       }
    }
}                此帖出自小平头技术问答