直接访问物理地址下的数据

1、访问硬件指定内存下的数据

1、如设备ID号：

#include  <REGX52.H>
#include  "LCD1602.h"




/*
LCD1602打印单片机的ID号
*/


void main()
{
		unsigned char *p;
		unsigned char code *x;         //访问程序存储区
		
		LCD_Init();
//		LCD_ShowString(1,1,"HelloWorld!");
	
		p = (unsigned char *)0xF1;     //RAM区的ID号
		x = (unsigned char *)0x1FF9;   //8k程序存储区(flash)  0x1FF9为ROM区ID地址
	/*RAM区与ROM区ID号相同*/
		LCD_ShowHexNum(1,1,*p,2);
		LCD_ShowHexNum(1,3,*(p+1),2);
		LCD_ShowHexNum(1,5,*(p+2),2);
		LCD_ShowHexNum(1,7,*(p+3),2);
		LCD_ShowHexNum(1,9,*(p+4),2);
		LCD_ShowHexNum(1,11,*(p+5),2);
		LCD_ShowHexNum(1,13,*(p+6),2);
	
		LCD_ShowHexNum(2,1,*x,2);
		LCD_ShowHexNum(2,3,*(x+1),2);
		LCD_ShowHexNum(2,5,*(x+2),2);
		LCD_ShowHexNum(2,7,*(x+3),2);
		LCD_ShowHexNum(2,9,*(x+4),2);
		LCD_ShowHexNum(2,11,*(x+5),2);
		LCD_ShowHexNum(2,13,*(x+6),2);
	
	
		while(1)
		{
				
		}
	
}

2、将复杂格式的数据转换为字节，方便通信与存储

#include <stdio.h>

/*将复杂格式的数据转换为字节，方便通信与存储*/
/*用指针将float型数据发送至单片机*/

/*
float型   ->    数组    ->      float型
*/

/*******************************/

unsigned char AirData[20];
unsigned char DataReceive[4];
/*发送数据*/
void SendData(const unsigned char *data,unsigned char count)
{
	unsigned char i;
	for(i=0;i<count;i++)
	{
		AirData[i]=data[i];          //将转换为数组的地址赋值给数组AirData[]
	}
}
/*接收数据*/
void ReceiveData(unsigned char *data,unsigned char count)
{
	unsigned char i;
	for(i=0;i<count;i++)
	{
		data[i]=AirData[i];          //数据接收
	}
}

/*******************************/

int  main(void)
{
	float  num = 0.125;
	float *fp;
	unsigned char i;
	unsigned char *p;

	p = (unsigned char *)&num;      //指针初始化   （unsigned char *）强制类型转化为同一级别

	SendData(p,4);                  //（不用理解，拿去用）发送数组地址值  将浮点型数据(0.125) 转化为 四个字节的数组（float) 为四字节

	/*****************************/
	printf("\nAirData=");
	for(i=0;i<4;i++)
	{
		printf("%x",AirData[i]);
	}
	/****************************/

	ReceiveData(DataReceive,4);   //读取数据

	fp = (float *)DataReceive;    //在转化为float型数据

	printf("\nnum=%f",*fp);
	return 0;
}