mcs51单片机使用串口进行通信

#define uchar unsigned char 

#include "string.h" 

#include "reg51.h" 
sbit P1_0=P1^0;
sbit P2_7=P2^7;
sbit P2_5=P2^5;
sbit P1_7=P1^7;
sbit P1_1=P1^1;

void SendData(uchar Dat) 

{ 	uchar i=0; 

	SBUF=Dat; 

	while(1 == 1){ 
		if(TI == 1) 	
		{ 	 
			TI=0;
			 break;
		}
	}
 

} 

void mDelay(unsigned int DelayTime) 
{ unsigned char j=0; 

	for(;DelayTime>0;DelayTime--) 
	{ 
		for(j=0;j<125;j++) 
		{;} 	
	} 

} 

uchar Key() 
{ 		 
	uchar row,colum;
	P2 = 0x0f;
	if( P2 != 0x0f)
	{
		if(P2 == 0x07) row = 0;
		if(P2 == 0x0b) row = 1;
		if(P2 == 0x0d) row = 2;
		if(P2 == 0x0e) row = 3;

		P2 = 0xf0;
		if(P2 != 0xf0)
		{
			if(P2 == 0x70) colum = 0;
			if(P2 == 0xb0) colum = 1;
			if(P2 == 0xd0) colum = 2;
			if(P2 == 0xe0) colum = 3;
			
			P2 = 0x0f;
			while(P2 != 0x0f);
			return (row*4+colum);
		}
		else 
			return (0xff);
	}

	return(0xff); 
} 

void main() 

{ 
		uchar KeyValue[4],pos,i,j; 
		uchar identify[4];
		uchar send;
		uchar Get;
		P1=0x00; 		//关闭 

		TMOD=0x20; 		//确定定时器工作模式 
		TH1=0xe8; 
		TL1=0xe8; 		//定时初值 
		PCON&=0x80; 		//SMOD=1 
		TR1=1; 				//开启定时器 1
		SCON=0x40;		 //串口工作方式 1 
		REN=1; 				//允许接收 
		RI = 0;
		P2_7=0;
		P2_5=1;

	

		//工作循环
		P2_7=0;
		P2_5=0;

		for(;;) 
		{ 
				
				P1_7=1;
				mDelay(0x01);
				SendData(0x04);
				mDelay(0x01);
				P1_7=0;
				mDelay(0xff);mDelay(0xff);

				if(RI)
				{
					Get = SBUF;
					SendData(Get);
					P1_0=1;
					P1_1=0;
					RI = 0;
				}

			mDelay(0xff);mDelay(0xff);
			

		} 

}