module knight_rider(
    input clk, rst,
    output [7:0] r
);

// másodperces engedélyező jel
reg [25:0] cntr = 0;
wire en = (cntr == 9/*49999999*/); // 1 Hz

always @(posedge clk)
       if (rst | en)
               cntr <= 0;
       else
               cntr <= cntr + 1;


reg [7:0] shr = 8'b00000001;
reg dir = 0;

wire first = (shr[1] == 1);
wire last  = (shr[6] == 1);

// shiftelés iránya
always @(posedge clk)
  if ( rst )
    dir <= 0;
  else if ( en )
    if ( (first & dir) | (last & !dir) )
      dir <= ~dir;

// shiftelés
always @(posedge clk)
  if ( rst )
    shr <= 8'b00000001;
  else if ( en )
    if ( dir ) // jobbra
      shr <= { shr[0], shr[7:1] };
    else       // balra
      shr <= { shr[6:0], shr[7] };

assign r = shr;

endmodule