reg51.h
at89x51.h文件中对P1.1的操作是写成P1_1
reg51.h文件中对P1.1的操作是写成P1^1
定义，sbit 的用法有三种：
第一种方法：sbit 位变量名＝地址值
第二种方法：sbit 位变量名＝SFR 名称^变量位地址值
第三种方法：sbit 位变量名＝SFR 地址值^变量位地址值
如定义PSW 中的OV 可以用以下三种方法：
sbit OV=0xd2 （1）说明：0xd2 是OV 的位地址值
sbit OV=PSW^2 （2）说明：其中PSW 必须先用sfr 定义好
sbit OV=0xD0^2 （3）说明：0xD0 就是PSW 的地址值
因此这里用sfr P1_0=P1^0;就是定义用符号P1_0 来表示P1.0 引脚，如果你愿意也可以起P10 一类的名字，只要下面程序中也随之更改就行了。
1 //Time:2017-2-11
2 //Project Name:reg51.h
3 //write by:cyt
4 /*---------------------------------------------------------
5 REG51.H
6 Header file for generic 80C51 and 80C31 microcontroller.
7 Copyright (c) 1988-2002 Keil Elektronik GmbH and Keil Software, Inc.
8 All rights reserved.
9 ------------------------------------------------------------*/
10 #ifndef __REG51_H__
11 #define __REG51_H__
12 /* BYTE Register */
13 sfr P0 = 0x80;
14 sfr P1 = 0x90;
15 sfr P2 = 0xA0;
16 sfr P3 = 0xB0;
17 sfr PSW = 0xD0;
18 sfr ACC = 0xE0;
19 sfr B = 0xF0;
20 sfr SP = 0x81;
21 sfr DPL = 0x82;
22 sfr DPH = 0x83;
23 sfr PCON = 0x87;
24 sfr TCON = 0x88;
25 sfr TMOD = 0x89;
26 sfr TL0 = 0x8A;
27 sfr TL1 = 0x8B;
28 sfr TH0 = 0x8C;
29 sfr TH1 = 0x8D;
30 sfr IE = 0xA8;
31 sfr IP = 0xB8;
32 sfr SCON = 0x98;
33 sfr SBUF = 0x99;
34 /* BIT Register */
35 /* PSW */
36 sbit CY = 0xD7;
37 sbit AC = 0xD6;
38 sbit F0 = 0xD5;
39 sbit RS1 = 0xD4;
40 sbit RS0 = 0xD3;
41 sbit OV = 0xD2;
42 sbit P = 0xD0;
43 /* TCON */
44 sbit TF1 = 0x8F;
45 sbit TR1 = 0x8E;
46 sbit TF0 = 0x8D;
47 sbit TR0 = 0x8C;
48 sbit IE1 = 0x8B;
49 sbit IT1 = 0x8A;
50 sbit IE0 = 0x89;
51 sbit IT0 = 0x88;
52 /* IE */
53 sbit EA = 0xAF;
54 sbit ES = 0xAC;
55 sbit ET1 = 0xAB;
56 sbit EX1 = 0xAA;
57 sbit ET0 = 0xA9;
58 sbit EX0 = 0xA8;
59 /* IP */
60 sbit PS = 0xBC;
61 sbit PT1 = 0xBB;
62 sbit PX1 = 0xBA;
63 sbit PT0 = 0xB9;
64 sbit PX0 = 0xB8;
65 /* P3 */
66 sbit RD = 0xB7;
67 sbit WR = 0xB6;
68 sbit T1 = 0xB5;
69 sbit T0 = 0xB4;
70 sbit INT1 = 0xB3;
71 sbit INT0 = 0xB2;
72 sbit TXD = 0xB1;
73 sbit RXD = 0xB0;
74 /* SCON */
75 sbit SM0 = 0x9F;
76 sbit SM1 = 0x9E;
77 sbit SM2 = 0x9D;
78 sbit REN = 0x9C;
79 sbit TB8 = 0x9B;
80 sbit RB8 = 0x9A;
81 sbit TI = 0x99;
82 sbit RI = 0x98;
83 #endif