Top secrets sources NedoPC pentevo

`include "../include/tune.v"

// PentEvo project (c) NedoPC 2010
//
// generates horizontal vga sync, double the rate of TV horizontal sync
//
// KVIK PHEEKS just to double HSYNC not scan-doubling
// beginning  of every other vga_hsync coincides with beginning of tv_hsync
// length is HSYNC_END clocks @ 28mhz

module vga_synch(

        input clk,

        output reg  vga_hsync,

        output reg scanout_start,

        input  wire hsync_start
);


//      localparam HSYNC_BEG = 9'd00;
//      localparam HSYNC_END = 10'd96;

//      localparam SCANOUT_BEG = 10'd112;

        localparam HSYNC_END    = 10'd106;
        localparam SCANOUT_BEG  = 10'd159;

        localparam HPERIOD = 10'd896;


        reg [9:0] hcount;




        initial
        begin
                hcount = 9'd0;
                vga_hsync = 1'b0;
        end



        always @(posedge clk)
        begin
                        if( hsync_start )
                                hcount <= 10'd2;
                        else if ( hcount==(HPERIOD-9'd1) )
                                hcount <= 10'd0;
                        else
                                hcount <= hcount + 9'd1;
        end


        always @(posedge clk)
        begin
                if( !hcount )
                        vga_hsync <= 1'b1;
                else if( hcount==HSYNC_END )
                        vga_hsync <= 1'b0;
        end


        always @(posedge clk)
        begin
                if( hcount==SCANOUT_BEG )
                        scanout_start <= 1'b1;
                else
                        scanout_start <= 1'b0;
        end


endmodule