/* SE1.C  rs232 */
/*  PC <--> 8051 RS232 COM1  <9600 N 8 1> */

#define op outportb
#define ip inportb

#include <bios.h>
#include <stdio.h>
/*-----------------------------*/
main()
{
unsigned char c;

 init_232();
 clrscr();
 puts("---------------------------------------");
 puts("SE1.EXE    PC RS232  COM1  <9600 N 8 1> ");
 puts("---------------------------------------");

 while(1)
  {
/* check any valid data in */
    c=ip(0x3fd);
    if( (c & 0x01)== 0x01)
     { c=ip(0x3f8);  printf("%c",c);  }

/* check user key in */
   if( kbhit() )
    {
     c=getch();
     switch(c)
      {
       case ' ':
       clrscr();
       puts("--------------------------------------");
       puts("SE1.EXE    PC RS232  COM1  <9600 N 8 1>");
       puts("--------------------------------------");
       break;

       case 27 : exit(0);  break;
       default : printf("%c", c);
		 tx(c);
		 break;
      }
    }
 }

}
/*---------------------------------------------*/
init_232()
{
  op(0x3fb, 0x80);
  op(0x3f8, 0x0c);
  op(0x3f9, 0	);

  op(0x3fb, 0x03);
  op(0x3fc, 0x02);
  op(0x3f9, 0	);
}
/*----------------------------------------------*/
/* in 3fd bit1=1  have data in from 3f8 */
char rx()
{
char in;
 while(1)
  {
   if(kbhit()) { getch(); break; }
   in=ip(0x3fd);
   if( (in & 0x01)== 0x01)
     { in=ip(0x3f8);  return(in);   }
  }
}
/*---------------------------------------*/
/* in 3fd bit5=1  7654	op to 3f8 */
tx(char c)
{
char in;
 while(1)
  {
   in=ip(0x3fd);
   if( (in & 0x20)== 0x20 )
     { op(0x3f8, c);  break;  }
  }
}
/*-------------------------------------------*/