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

// PentEvo project (c) NedoPC 2008-2009
//
// vertical blank, sync and window. H is period of horizontal sync;
// from the last non-blanked line:
// 3H is pre-blank,
// 2.xxH is vertical sync (slightly more than 2H, all hsync edges preserved)
// vblank is total of 25H

module syncv(

        input clk,

        input hsync_start, // synchronizing signal
        input line_start,  // to end vsync some time after hsync has ended

        input hint_start,


        output reg vblank,
        output reg vsync,

        output reg int_start, // one-shot positive pulse marking beginning of INT for Z80

        output reg vpix // vertical picture marker: active when there is line with pixels in it, not just a border. changes with hsync edge
);





        localparam VBLNK_BEG = 9'd00;
        localparam VSYNC_BEG = 9'd08;
        localparam VSYNC_END = 9'd11;
        localparam VBLNK_END = 9'd32;

        localparam INT_BEG = 9'd16;   // 9'd16 Scorpion 9'd0 pentagon

        localparam VPIX_BEG = 9'd080;//9'd064;
        localparam VPIX_END = 9'd272;//9'd256;

        localparam VPERIOD = 9'd312; // 320 pentagono foreva! 9d'313 Scorpion foreva!!!


        reg [8:0] vcount;




        initial
        begin
                vcount = 9'd0;
                vsync = 1'b0;
                vblank = 1'b0;
                vpix = 1'b0;
                int_start = 1'b0;
        end

        always @(posedge clk) if( hsync_start )
        begin
                if( vcount==(VPERIOD-9'd1) )
                        vcount <= 9'd0;
                else
                        vcount <= vcount + 9'd1;
        end



        always @(posedge clk) if( hsync_start )
        begin
                if( vcount==VBLNK_BEG )
                        vblank <= 1'b1;
                else if( vcount==VBLNK_END )
                        vblank <= 1'b0;
        end


        always @(posedge clk)
        begin
                if( (vcount==VSYNC_BEG) && hsync_start )
                        vsync <= 1'b1;
                else if( (vcount==VSYNC_END) && line_start  )
                        vsync <= 1'b0;
        end


        always @(posedge clk)
        begin
                if( (vcount==INT_BEG) && hint_start )
                        int_start <= 1'b1;
                else
                        int_start <= 1'b0;
        end



        always @(posedge clk) if( hsync_start )
        begin
                if( vcount==VPIX_BEG )
                        vpix <= 1'b1;
                else if( vcount==VPIX_END )
                        vpix <= 1'b0;
        end


endmodule