从头文件中学习sfr和sbit

1、reg52.h

头文件，它定义了单片机的一些端口物理地址。

#ifndef __REG52_H__
#define __REG52_H__

/*  BYTE Registers  */
sfr P0    = 0x80;
sfr P1    = 0x90;
sfr P2    = 0xA0;
sfr P3    = 0xB0;
sfr PSW   = 0xD0;
sfr ACC   = 0xE0;
sfr B     = 0xF0;
sfr SP    = 0x81;
sfr DPL   = 0x82;
sfr DPH   = 0x83;
sfr PCON  = 0x87;
sfr TCON  = 0x88;
sfr TMOD  = 0x89;
sfr TL0   = 0x8A;
sfr TL1   = 0x8B;
sfr TH0   = 0x8C;
sfr TH1   = 0x8D;
sfr IE    = 0xA8;
sfr IP    = 0xB8;
sfr SCON  = 0x98;
sfr SBUF  = 0x99;

/*  8052 Extensions  */
sfr T2CON  = 0xC8;
sfr RCAP2L = 0xCA;
sfr RCAP2H = 0xCB;
sfr TL2    = 0xCC;
sfr TH2    = 0xCD;


/*  BIT Registers  */
/*  PSW  */
sbit CY    = PSW^7;
sbit AC    = PSW^6;
sbit F0    = PSW^5;
sbit RS1   = PSW^4;
sbit RS0   = PSW^3;
sbit OV    = PSW^2;
sbit P     = PSW^0; //8052 only

/*  TCON  */
sbit TF1   = TCON^7;
sbit TR1   = TCON^6;
sbit TF0   = TCON^5;
sbit TR0   = TCON^4;
sbit IE1   = TCON^3;
sbit IT1   = TCON^2;
sbit IE0   = TCON^1;
sbit IT0   = TCON^0;

/*  IE  */
sbit EA    = IE^7;
sbit ET2   = IE^5; //8052 only
sbit ES    = IE^4;
sbit ET1   = IE^3;
sbit EX1   = IE^2;
sbit ET0   = IE^1;
sbit EX0   = IE^0;

/*  IP  */
sbit PT2   = IP^5;
sbit PS    = IP^4;
sbit PT1   = IP^3;
sbit PX1   = IP^2;
sbit PT0   = IP^1;
sbit PX0   = IP^0;

/*  P3  */
sbit RD    = P3^7;
sbit WR    = P3^6;
sbit T1    = P3^5;
sbit T0    = P3^4;
sbit INT1  = P3^3;
sbit INT0  = P3^2;
sbit TXD   = P3^1;
sbit RXD   = P3^0;

/*  SCON  */
sbit SM0   = SCON^7;
sbit SM1   = SCON^6;
sbit SM2   = SCON^5;
sbit REN   = SCON^4;
sbit TB8   = SCON^3;
sbit RB8   = SCON^2;
sbit TI    = SCON^1;
sbit RI    = SCON^0;

/*  P1  */
sbit T2EX  = P1^1; // 8052 only
sbit T2    = P1^0; // 8052 only
             
/*  T2CON  */
sbit TF2    = T2CON^7;
sbit EXF2   = T2CON^6;
sbit RCLK   = T2CON^5;
sbit TCLK   = T2CON^4;
sbit EXEN2  = T2CON^3;
sbit TR2    = T2CON^2;
sbit C_T2   = T2CON^1;
sbit CP_RL2 = T2CON^0;

#endif

头文件我们可以学习到：

1、头文件格式

#ifndef xx名称xxx

#define xx名称xxx

xxxxxxx内容xxxxxxxxxx

#endif

（文件保存为reg52.h,并在引用文件中添加“#include "reg52.h"”）

2、sfr和sbit

sfr（Speical Function Register特殊功能寄存器的简称），它是单片计算机中的一组特殊的临时存储区域，用于动态存放计算机运行过程的一些状态信息、并依此做相应的控制。对于SFR是固定的，是在单片机设计时定义好的，只需添加对应的头文件即可。当然，再没有被定义的区间我们可以采用sfr来定义，如

sfr P1 = 0x90; //定义P1 I/O 口,其地址90H ( 该常数必须在特殊功能寄存器的地址范围之内(80H-FFH) ).

sbit 可定义位寻址对象.如访问特殊功能寄存器中的某位。如

sft P1 = 0x90;

sbit P1_1 = P1 ^ 1; //先定义一个特殊功能寄存器名再指定位变量名所在的位置,当可寻址位位于特殊功能寄存器中时可采用这种方法

或者用sbit P1_1 = 0x90 ^ 1，是一样的效果