// Keys off of HSync and VSync signals to get the actual electron
// beam position

module VGA_Current_Beam_Position(
  input i_Clk,
  input i_HSync,
  input i_VSync,

  output reg o_HSync = 0,
  output reg o_VSync = 0,

  output reg [$clog2(TOTAL_COLUMNS)-1:0] o_X,
  output reg [$clog2(TOTAL_ROWS)-1:0] o_Y
);
  parameter TOTAL_COLUMNS = 800;
  parameter TOTAL_ROWS = 525;

  wire w_frameStart;

  // forward these flip-flop style. use these instead of what
  // comes out of sync pulse generator!
  always @(posedge i_Clk) begin
    o_VSync <= i_VSync;
    o_HSync <= i_HSync;
  end

  always @(posedge i_Clk) begin
    if (w_frameStart == 1) begin
      o_X <= 0;
      o_Y <= 0;
    end else begin
      if (o_X == TOTAL_COLUMNS - 1) begin
        o_X <= 0;
        if (o_Y == TOTAL_ROWS - 1) begin
          o_Y <= 0;
        end else begin
          o_Y <= o_Y + 1;
        end
      end else begin
        o_X <= o_X + 1;
      end
    end
  end

  // rising vsync == new frame
  assign w_frameStart = (~o_VSync & i_VSync);
endmodule