一个项目的一部分内容，让初学者模拟着做一下，还是很有用处的。

这样的程序可以实现一个51单片机有两个串口

#include<regx52.h>

sbit BT_SND =P1^1;
sbit BT_REC =P1^0;

//1602部分引脚定义
sbit LCM_RW =P2^1 ;//定义引脚
sbit LCM_RS =P2^0;
sbit LCM_E =P2^2;
#define LCM_Data P0
#define Busy 0x80 //用于检测LCM状态字中的Busy标识

#define F_TM F0

#define TIMER0_ENABLE   TL0=TH0; TR0=1;
#define TIMER0_DISABLE TR0=0;

void WriteDataLCM(unsigned char WDLCM);
void WriteCommandLCM(unsigned char WCLCM,BuysC);
unsigned char ReadDataLCM(void);
unsigned char ReadStatusLCM(void);
void LCMInit(void);
void DisplayOneChar(unsigned char X, unsigned char Y, unsigned char DData);
void DisplayListChar(unsigned char X, unsigned char Y, unsigned char code *DData);
void Delay5Ms(void);
void Delay400Ms(void);

unsigned char code qq[] = {"Receive_Data"};
//unsigned char code tel[] = {"Command:"};

sbit ACC0=    ACC^0;
sbit ACC1=    ACC^1;
sbit ACC2=    ACC^2;
sbit ACC3=    ACC^3;
sbit ACC4=    ACC^4;
sbit ACC5=    ACC^5;
sbit ACC6=    ACC^6;
sbit ACC7=    ACC^7;

void IntTimer0() interrupt 1
{
F_TM=1;
}

//发送一个字符
void PSendChar(unsigned char inch)
{
ACC=inch;

F_TM=0;
BT_SND=0; //start bit
TIMER0_ENABLE; //启动
while(!F_TM);

BT_SND=ACC0; //先送出低位
F_TM=0;
while(!F_TM);

BT_SND=ACC1;
F_TM=0;
while(!F_TM);

BT_SND=ACC2;
F_TM=0;
while(!F_TM);

BT_SND=ACC3;
F_TM=0;
while(!F_TM);

BT_SND=ACC4;
F_TM=0;
while(!F_TM);

BT_SND=ACC5;
F_TM=0;
while(!F_TM);

BT_SND=ACC6;
F_TM=0;
while(!F_TM);

BT_SND=ACC7;
F_TM=0;
while(!F_TM);

BT_SND=1;
F_TM=0;
while(!F_TM);

TIMER0_DISABLE; //停止timer

}

//接收一个字符
unsigned char PGetChar()
{
TIMER0_ENABLE;
F_TM=0;
while(!F_TM); //等过起始位
ACC0=BT_REC;

TL0=TH0;

F_TM=0;
while(!F_TM);
ACC1=BT_REC;

F_TM=0;
while(!F_TM);
ACC2=BT_REC;

F_TM=0;
while(!F_TM);
ACC3=BT_REC;

F_TM=0;
while(!F_TM);
ACC4=BT_REC;

F_TM=0;
while(!F_TM);
ACC5=BT_REC;

F_TM=0;
while(!F_TM);
ACC6=BT_REC;

F_TM=0;
while(!F_TM);
ACC7=BT_REC;

F_TM=0;

while(!F_TM)
{
if(BT_REC)
{
break;
}
}
TIMER0_DISABLE; //停止timer
return ACC;

}
//检查是不是有起始位
bit StartBitOn()
{
return(BT_REC==0);

}
void main()
{
unsigned char gch,i;

TMOD=0x22; /*定时器1为工作模式2(8位自动重装)，0为模式2(8位自动重装) */

PCON=00;

TR0=0; //在发送或接收才开始使用
TF0=0;
TH0=(256-96); //9600bps 就是 1000000/9600=104.167微秒 执行的timer是104.167*11.0592/12= 96

//

TL0=TH0;
ET0=1;
EA=1;
Delay400Ms(); //启动等待，等LCM讲入工作状态
   LCMInit(); //LCM初始化
   Delay5Ms(); //延时片刻(可不要)
   DisplayListChar(2, 0, qq);
//    DisplayListChar(0, 1, tel);
   // ReadDataLCM();//测试用句无意义
PSendChar(0x55);
PSendChar(0xaa);
PSendChar(0x00);
PSendChar(0xff);

while(1)
{

if(StartBitOn())
   {
   gch=PGetChar();
   PSendChar(gch);
   for(i=0;i<8;i++)
      DisplayOneChar(7-i,1, ((gch>>i)&0x01)+48);
  
    }
}
}

//写数据
void WriteDataLCM(unsigned char WDLCM)
{
ReadStatusLCM(); //检测忙
LCM_Data = WDLCM;
LCM_RS = 1;
LCM_RW = 0;
LCM_E = 0; //若晶振速度太高可以在这后加小的延时
LCM_E = 0; //延时
LCM_E = 1;
}

//写指令
void WriteCommandLCM(unsigned char WCLCM,BuysC) //BuysC为0时忽略忙检测
{
if (BuysC) ReadStatusLCM(); //根据需要检测忙
LCM_Data = WCLCM;
LCM_RS = 0;
LCM_RW = 0;
LCM_E = 0;
LCM_E = 0;
LCM_E = 1;
}

/*/读数据
unsigned char ReadDataLCM(void)
{
LCM_RS = 1;
LCM_RW = 1;
LCM_E = 0;
LCM_E = 0;
LCM_E = 1;
return(LCM_Data);
}
*/
//读状态
unsigned char ReadStatusLCM(void)
{
LCM_Data = 0xFF;
LCM_RS = 0;
LCM_RW = 1;
LCM_E = 0;
LCM_E = 0;
LCM_E = 1;
while (LCM_Data & Busy); //检测忙信号
return(LCM_Data);
}

void LCMInit(void) //LCM初始化
{
LCM_Data = 0;
WriteCommandLCM(0x38,0); //三次显示模式设置，不检测忙信号
Delay5Ms();
WriteCommandLCM(0x38,0);
Delay5Ms();
WriteCommandLCM(0x38,0);
Delay5Ms();

WriteCommandLCM(0x38,1); //显示模式设置,开始要求每次检测忙信号
WriteCommandLCM(0x08,1); //关闭显示
WriteCommandLCM(0x01,1); //显示清屏
WriteCommandLCM(0x06,1); // 显示光标移动设置
WriteCommandLCM(0x0C,1); // 显示开及光标设置
}

//按指定位置显示一个字符
void DisplayOneChar(unsigned char X, unsigned char Y, unsigned char DData)
{
Y &= 0x1;
X &= 0xF; //限制X不能大于15，Y不能大于1
if (Y) X |= 0x40; //当要显示第二行时地址码+0x40;
X |= 0x80; //算出指令码
WriteCommandLCM(X, 0); //这里不检测忙信号，发送地址码
WriteDataLCM(DData);
}

//按指定位置显示一串字符
void DisplayListChar(unsigned char X, unsigned char Y, unsigned char code *DData)
{
unsigned char ListLength;

ListLength = 0;
Y &= 0x1;
X &= 0xF; //限制X不能大于15，Y不能大于1
while (DData[ListLength]>0x20) //若到达字串尾则退出
{
if (X <= 0xF) //X坐标应小于0xF
{
DisplayOneChar(X, Y, DData[ListLength]); //显示单个字符
ListLength++;
X++;
}
}
}

//5ms延时
void Delay5Ms(void)
{
unsigned int TempCyc = 5552;
while(TempCyc--);
}

//400ms延时
void Delay400Ms(void)
{
unsigned char TempCycA = 5;
unsigned int TempCycB;
while(TempCycA--)
{
TempCycB=7269;
while(TempCycB--);
};
}