模拟串口的实现单片机IO口

一般的单片机都只有一个串口，所以必须模拟一个出来。

/*

  sbit TXD1  = P1^4;                  //define p14 as the analog transmit port

  sbit RXD1  = P1^2;                  //define p12 as the analog recieve port

*/

#include "REG52.H"

#define uint unsigned int

#define uchar unsigned char

#include

 void WaitTF0(void);

 void TIMEINI(void)               //counter initial

  {

    TMOD=0x02;

    TH0=0xA0;                           、//9600 BPS

       TL0=TH0;

       TR0=1;

       TF0=0;

   }

   void WByte(uchar input)           //  send function

   {

         uchar i=8;

              TR0=1;

              TXD1=0;                                          //begin bit

              WaitTF0();

                                                 //send the Byte

           while(i--)

            {

                     TXD1=input&0x01;                    //send Byte from low bit to high bit

                      WaitTF0();                               

                      input=input>>1;                     //right shift

          }

               TXD1=1;                                         //stop bit

              WaitTF0();

              TR0=0;                                           //stop the counter

   }

       uchar RByte()            //the recieve function

   {

         uchar Output=0;

          uchar i=8;

               while(RXD1);                          

                    i=i;

                     i=i;

                     i=i;

                     i=i;

                     i=i;

                     i=i;

                     i=i;

                     TR0=1;                                 //计数器开始工作

                  WaitTF0();

           while(i--)                                                           // 接收8位数据位

            {

                      Output>>=1;

                      if(RXD1)Output=Output|0x80;   //recieve from the high bit to low bit

             WaitTF0();

          }

              TR0=0;

               return  Output;

   }

  void WaitTF0(void)                         //check the counter

  {

             while(!TF0);

             TF0=0;

  }