// ZX-Evo Base Configuration (c) NedoPC 2008,2009,2010,2011,2012,2013,2014
//
// generates horizontal vga sync, double the rate of TV horizontal sync
/*
This file is part of ZX-Evo Base Configuration firmware.
ZX-Evo Base Configuration firmware is free software:
you can redistribute it and/or modify it under the terms of
the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
ZX-Evo Base Configuration firmware is distributed in the hope that
it will be useful, but WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with ZX-Evo Base Configuration firmware.
If not, see <http://www.gnu.org/licenses/>.
*/
`include "../include/tune.v"
module video_vga_sync_h(
input wire clk,
output reg vga_hsync,
output reg scanout_start,
input wire hsync_start
);
localparam HSYNC_END = 10'd106;
localparam SCANOUT_BEG = 10'd156;
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