My COM cable has just 3 line GND,RxD and TxD . I want to write a byte in to COM port on PC . Who can tell me , is it possible ?
If yes , tell me are my codes wrong ?
They here :

C program in PC to read 1 byte :
#include <stdio.h>
#include <conio.h>
main()
{
int i,j,k;
for (k=1;k<=10000;k++)
{
for(j=1;j<=1000;j++)
{
i=inp(0x02F8);
if (i != 0)
printf("%i",i);
}
}
printf("bye");
getch();
}

And program in 51 :

cseg at 0

Setb 98h.6
Clr 98h.7
mov 89h,#32
mov 93h,#253
Mov 87h,#128

MOV 99h,#'A'

end


Thanks a lot .