#include <reg51.h>
sbit BT_SND =P1^0;
sbit BT_REC =P1^1;
//********************************************** 
//IO 口模擬232通訊程序 使用兩種方式的C程序 
//占用定時器0 
//**********************************************
#define MODE_QUICK
#define F_TM F0
#define TIMER0_ENABLE  TL0=TH0; TR0=1;
#define TIMER0_DISABLE TR0=0;

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;
}
//發送一個字符
void PSendChar(unsigned char inch)
{
#ifdef MODE_QUICK 
ACC=inch;

F_TM=0;
BT_SND=0; //start bit 
TIMER0_ENABLE; //啟動
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

#else
unsigned char ii;
ii=0;
F_TM=0;
BT_SND=0; //start bit 
TIMER0_ENABLE; //啟動

while(!F_TM);
while(ii<8)
{
if(inch&1)
{
BT_SND=1;
}
else
{
BT_SND=0;
}
F_TM=0;
while(!F_TM);
ii++;
inch>>=1;
}
BT_SND=1; 
F_TM=0;

while(!F_TM);
#endif 
TIMER0_DISABLE; //停止timer
}
//接收一個字符
unsigned char PGetChar()
{
#ifdef MODE_QUICK 

TIMER0_ENABLE; 
F_TM=0;
while(!F_TM); //等過起始位
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;
#else
unsigned char rch,ii;
TIMER0_ENABLE; 
F_TM=0;
ii=0;
rch=0;
while(!F_TM); //等過起始位

while(ii<8)
{
rch>>=1;
if(BT_REC)
{
rch|=0x80;
}
ii++;
F_TM=0;
while(!F_TM);

}
F_TM=0;
while(!F_TM)
{
if(BT_REC)
{
break;
}

}
TIMER0_DISABLE; //停止timer
return rch;

#endif 

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

}
void main()
{
unsigned char gch;

TMOD=0x22; /*定時器1為工作模式2(8位自動重裝)，0為模式2(8位
自動重裝) */
PCON=00;

TR0=0; //在發送或接收才開始使用
TF0=0; 
TH0=(256-96); //9600bps 就是 1000000/9600=104.167微秒 執行的
timer是
//             
104.167*11.0592/12= 96 
TL0=TH0;
ET0=1;
EA=1;

PSendChar(0x55);
PSendChar(0xaa);
PSendChar(0x00);
PSendChar(0xff);

while(1)
{
if(StartBitOn())
{
gch=PGetChar();
PSendChar(gch);
}
}

}