unit spkutil;

interface

 procedure speaker_on;
 procedure speaker_off;
 procedure speaker_freq(freq:word);
function spk_stat:byte;

implementation

 procedure speaker_on;
 begin
  asm
           in al,61h
           or al,3
           out 61h,al
  end;
 end;

 procedure speaker_off;
 begin
  asm
           in al,61h
           and al,0fch
           out 61h,al
  end;
 end;

 procedure speaker_freq(freq:word);
 const
  timer_clock   = 1193180;
 type
  wrd           = record
                  lo    : byte;
                  hi    : byte;
                  end;

 var
  count         : word;
 begin
 if freq>18 then count:=round((timer_clock/freq)) else count:=0;
 asm
    pushf
    push ax
    cli
    mov  al,(2 shl 6)+(3 shl 4)+(3 shl 1)+(0 shl 0)
    out  43h,al
    mov  al,wrd(count).lo
    out  42h,al
    mov  al,wrd(count).hi
    out  42h,al
    pop  ax
    popf
 end;
end;

function spk_stat:byte;
begin
  port[$43]:=128+64+8;{128+64+32+8;}
  spk_stat:=((port[$42]) and 128) shr 7;
end;

end.