奇数分频器

本实验要实现奇数分频功能，运用错位“异或”法。

module clk_div_3(clk_in,rst_n,clk_out);
input clk_in;
input rst_n;
output clk_out;

parameter N = 7; //N is odd.
parameter M = (N-1)/2;

reg [2:0] cnt,cnt1;
reg clk_p,clk_n;

always @ (posedge clk_in) begin
    if(!rst_n) begin
        cnt <= 0;
        clk_p <= 0;
    end
    else begin
        if(cnt < M) begin
            clk_p <= 1;
            cnt <= cnt + 1;
        end
        else if(cnt >=M && cnt < N-1) begin
            clk_p <= 0;
            cnt = cnt + 1;
        end
        else cnt = 0;
    end
end

always @ (negedge clk_in) begin
    if(!rst_n) begin
        cnt1 <= 0;
        clk_n <= 0;
    end
    else begin
    if(cnt1 < M) begin
            clk_n <= 1;
            cnt1 <= cnt1 + 1;
    end
    else if(cnt1 >=M && cnt1 < N-1) begin
            clk_n <= 0;
            cnt1 = cnt1 + 1;
        end
        else cnt1 = 0;
    end
end

assign clk_out = clk_p | clk_n; //错位相或


endmodule

仿真结果：