實現預置計數器，當為7進位制時，直接修改資料位寬為3bit即可。

//實現可預置初值的15進位制迴圈計數器
module test (
    input clk,
    input rst,
    input [3:0]d_in,
    output reg [3:0]d_out
);
    reg [3:0]cnt;
    always @(posedge clk or negedge rst) begin
        if(!rst) begin
            cnt <= d_in;
        end
        else if (cnt == 'b1110) begin
 

            cnt <= 'b0;
        end
        else begin
            cnt <= cnt + 1'b1;
        end
    end
    always @(posedge clk or negedge rst) begin
        if(!rst) begin
            d_out <= 'b0;
        end
        else begin
            d_out <= cnt;
        end
    end
endmodule

`timescale 1ns/10ps
 
module test_tb;
    
    reg clk;
    reg rst;
    reg [3:0]d_in;
    wire [3:0]d_out;

    test u1(
    .clk(clk),
    .rst(rst),
    .d_in(d_in),
    .d_out(d_out)
);
    initial begin
        clk = 1'b1;
        rst = 1'b0;
        #8;
        rst = 1'b1;
    end
    always #5 clk = ~clk;

    initial
 
 begin
        d_in = 4'b0010;
    #10;
    end
endmodule