蓝桥杯基础模块9：蓝桥杯IO口扩展功能及存储器映射机制

    //头文件
    #include "reg52.h"
    //延时函数
    void Delay(unsigned int t)
    {
    	while(t--);
    	while(t--);
    }
    //573锁存器初始化选择
    void SelectHC573(unsigned char channel)
    {
    	switch(channel)
    	{
    	  case 4:
    		P2 = (P2 & 0x1f) | 0x80;
    	  break;
    	  case 5:
    		P2 = (P2 & 0x1f) | 0xa0;
    	  break;
    	  case 6:
    		P2 = (P2 & 0x1f) | 0xc0;
    	  break;
    	  case 7:
    		P2 = (P2 & 0