VGA_generator.v

// VGA 640*480 60Hz

module VGA_generator(clk, hsync, vsync, x_ptr, y_ptr, valid);

    input wire clk;
    output wire vsync, hsync, valid;
    output wire [9: 0] x_ptr, y_ptr;

    reg [9: 0] x_cnt, y_cnt;

    parameter
        HPIXELS = 10'd800,
        VLINES = 10'd521,
        HBP = 10'd144,
        HFP = 10'd784,
        VBP = 10'd31,
        VFP = 10'd511;

    always @(posedge clk) begin
        if (x_cnt == HPIXELS - 1)
            x_cnt <= 0;
        else
            x_cnt <= x_cnt + 1;
    end

    always @(posedge clk) begin
        if (y_cnt == VLINES - 1)
            y_cnt <= 0;
        else if (x_cnt == HPIXELS - 1)
            y_cnt <= y_cnt + 1;
    end

    assign valid = (x_cnt > HBP) && (x_cnt < HFP) && (y_cnt > VBP) && (y_cnt < VFP);

    assign hsync = (x_cnt >= 10'd96) ? 1'b1 : 1'b0;
    assign vsync = (y_cnt >= 10'd2) ? 1'b1 : 1'b0;

    assign x_ptr = x_cnt - HBP;
    assign y_ptr = y_cnt - VBP;

endmodule