[转载]用verilog写一段代码，实现消除一个glitch

滤掉小于1个周期glitch的原理图如下： verilog代码实现如下：

module digital_filter_(clk_in,rst,host_rst,host_rst_filter);
input  clk_in;
input  rst;
input  host_rst;
output host_rst_filter;

reg host_rst_d1;
reg host_rst_d2;

always@(posedge clk_in or negedge rst)
  begin
    if(~rst)
    begin
        host_rst_d1 <= 1b1;
        host_rst_d2 <= 1b1;
       end
    else
      begin
        host_rst_d1 <= host_rst;
        host_rst_d2 <= host_rst_d1;

      end
  end

assign host_rst_filter = host_rst_d1 | host_rst_d2;

endmodule

滤掉大于1个周期且小于2个周期glitch的原理图如下：

verilog代码实现如下：

module digital_filter_(clk_in,rst,host_rst,host_rst_filter);
input  clk_in;
input  rst;
input  host_rst;
output host_rst_filter;

reg host_rst_d1;
reg host_rst_d2;
reg host_rst_d3;

always@(posedge clk_in or negedge rst)
  begin
    if(~rst)
    begin
        host_rst_d1 <= 1b1;
        host_rst_d2 <= 1b1;
        host_rst_d3 <= 1b1;
      end
    else
  begin
        host_rst_d1 <= host_rst;
        host_rst_d2 <= host_rst_d1;
        host_rst_d3 <= host_rst_d2;
       end
  end

assign host_rst_filter = host_rst_d1 | host_rst_d2 | host_rst_d3;

endmodule