Program CardReader;
 
Uses Crt,Binary;
 
Const
   gameport=$201;
 
 
Procedure Wait_start;
Begin
   Repeat Until (Port[gameport] and 32)=0;
End;
 
Function data_readable:boolean;
Begin
   data_readable:=((Port[gameport] and 32)=0);
End;
 
Procedure Wait_clock;
Begin
   Repeat Until (Port[gameport] and 16)=0;
End;
 
Procedure Wait_clock_end;
Begin
   Repeat Until (Port[gameport] and 16)=16;
End;
 
Function data_input:byte;
Begin
   If (Port[gameport] and 64)=0 Then data_input:=0
      Else data_input:=1;
End;
 
Function card_at_end:boolean;
Begin
   card_at_end:=((Port[gameport] and 128)=0);
End;
 
Procedure test;
Begin
   Wait_start;
   Repeat
      Writeln(ByteBin(Port[$201]));
   Until keypressed;
End;
 
Begin
   ClrScr;
   Wait_start;
   While data_readable Do Begin
      Wait_clock;
      Write(data_input);
      Wait_clock_end;
   End;
   Repeat Until KeyPressed;
End.