//If there are 8 LEDs connected to the port B
//the lit LED will continuously move up and down
//(example for PIC target)

program SWAP;

var a16, b16: integer;
var i8: char;

procedure delay;
var i, j: char;
  begin
    i := 0;
    while i < 150 do
      begin
        i := i + 1;
        j := 0;
        while j < 200 do
          begin
            j := j + 1;
            nop;
          end;
      end;
  end;
  
procedure swap( var a, b: integer );
var tmp: integer;
begin
    tmp := a;
    a := b;
    b := tmp;
end;

begin
    //Initialization
    disable_interrupt( 'GIE' );
    set_bit( STATUS, 'RP0' );
    set_tris_a( 0 );
    set_tris_b( 0 );
    clear_bit( STATUS, 'RP0' );
    output_port_a( 0 );
    output_port_b( 0 );
    
    i8 := 0;
    
    while 1 do
    begin
      a16 := i8;
      b16 := 255 + i8;
      swap( a16, b16 );
      if ((b16 <> i8) or (a16 <> 255+i8)) then
      begin
          output_port_b( 255 );
          delay;
          output_port_b( 0 );
      end;
      i8 := i8 + 1;
      if i8 mod 2 then
          output_high_port_b( 7 );
      else
          output_low_port_b( 7 );
      delay;
    end;    
end.