8位同步码修改变4位同步码

 GV7704的1080p30及以下的分辨率同下码是这样的，每个同步码占用两个像素，而我们想要实现的是只占用一个像素。

实现方案：

检测到FF后可以计数,如data_dly 问题是怎样清除video数据中的FFh.

第二种方案是，用一个长度为8的reg [7:0] data_dly2 [7:0]当检测到FFFF00000000XYXY时，就对这8个寄存器赋值成我们想要的数据。 

module sync8_2_sync4(
input clk,
input [7:0] idata,
output [7:0] odata,
output h_out,
output v_out,
output sync_code

);

reg [7:0] din_buf [10:0] ;

reg [7:0] d_word_align = 0;
reg [1:0] v_h_buf =0;
reg [7:0] h_buf =0;
reg v_out_r=0;
reg h_out_r=0;
reg [3:0] cnt = 0;
reg sync_r = 1'b0;
always @( posedge clk )
begin
if( d_word_align[7:0] == 8'h7f || d_word_align == 8'hff) begin
din_buf[0] <= 8'h10;
din_buf[1] <= 8'h80;
din_buf[2] <= 8'h10;
din_buf[3] <= 8'h80;
din_buf[4] <= idata;
din_buf[5] <= 8'h00;
din_buf[6] <= 8'h00;
din_buf[7] <= 8'hff;
din_buf[8] <= din_buf[7];
end else if( &d_word_align[5:0] ) begin
din_buf[0] <= idata;
din_buf[1] <= 8'h00;
din_buf[2] <= 8'h00;
din_buf[3] <= 8'hff;
din_buf[4] <= 8'h10;
din_buf[5] <= 8'h80;
din_buf[6] <= 8'h10;
din_buf[7] <= 8'h80;
din_buf[8] <= din_buf[7];
end else begin
din_buf[0] <= idata;
din_buf[1] <= din_buf[0];
din_buf[2] <= din_buf[1];
din_buf[3] <= din_buf[2];
din_buf[4] <= din_buf[3];
din_buf[5] <= din_buf[4];
din_buf[6] <= din_buf[5];
din_buf[7] <= din_buf[6];
din_buf[8] <= din_buf[7];
end
end

always @( posedge clk )
begin
if( din_buf[5] == 8'hff )d_word_align[0] <= 1'b1;
else d_word_align[0] <= 1'b0;
end
always @( posedge clk )
begin
if( din_buf[4] == 8'hff )d_word_align[1] <= 1'b1;
else d_word_align[1] <= 1'b0;
end
always @( posedge clk )
begin
if( din_buf[3] == 8'h00 )d_word_align[2] <= 1'b1;
else d_word_align[2] <= 1'b0;
end
always @( posedge clk )
begin
if( din_buf[2] == 8'h00 )d_word_align[3] <= 1'b1;
else d_word_align[3] <= 1'b0;
end
always @( posedge clk )
begin
if( din_buf[1] == 8'h00 )d_word_align[4] <= 1'b1;
else d_word_align[4] <= 1'b0;
end
always @( posedge clk )
begin
if( din_buf[0] == 8'h00 )d_word_align[5] <= 1'b1;
else d_word_align[5] <= 1'b0;
end

always @( posedge clk )
begin
case(idata )
8'h80 :d_word_align[7:6] <= 2'b00;
8'h9d :d_word_align[7:6] <= 2'b01;
8'hab :d_word_align[7:6] <= 2'b10;
8'hb6 :d_word_align[7:6] <= 2'b11;
default :d_word_align[7:6] <= d_word_align[7:6];
endcase
end
always @( posedge clk )
begin
case(d_word_align[7:0])
8'h3f :v_h_buf <= 2'b00;
8'h7f :v_h_buf <= 2'b01 ;
8'hbf :v_h_buf <= 2'b10 ;
8'hff :v_h_buf <= 2'b11 ;
default :;
endcase
end
always @( posedge clk )
begin
case( cnt )
4'd0: if( (d_word_align[7:0] == 8'h3f) || (d_word_align[7:0] == 8'h7f) || (d_word_align[7:0] == 8'hbf) || (d_word_align[7:0] == 8'hff) )
cnt <= 1;
else cnt <= 0;
4'd1,4'd2,4'd3,4'd4: begin
cnt <= cnt + 1'b1;
if( v_h_buf[0] )
sync_r <= 1'b1;
else
sync_r <= 1'b0;
end

4'd5,4'd6,4'd7,4'd8: begin
cnt <= cnt + 1'b1;
if( v_h_buf[0] )
sync_r <= 1'b0;
else
sync_r <= 1'b1;
end
4'd9: begin
cnt <= 0;
sync_r <= 1'b0;
end
default:;
endcase
end

always @( posedge clk )
begin
h_buf[7:0] <= {h_buf[6:0],v_h_buf[0]};
end
always @( posedge clk )
begin
v_out_r <= v_h_buf[1];
h_out_r <= ~v_h_buf[0] ? h_buf[7] :v_h_buf[0];
end
assign odata = din_buf[8];
assign v_out = v_out_r;
assign h_out = h_out_r;
assign sync_code = sync_r;
endmodule