Devise different types of counters, for instance, a mod-15 counter that avoids 0, 3, 4, 8, and 5.

Question

Anonymous · Accepted Answer

module mod_15_counter (
  input wire clk,      // Clock signal
  input wire reset_n,  // Active low reset
  output reg [3:0] count // 4-bit counter output
);
  
  // Combinational logic to determine the next valid state
  always @(posedge clk or negedge reset_n) begin
    if (!reset_n)
      count <= 1;  // Start from 1 when reset is active
    else begin
      case (count)
        1: count <= 2;
        2: count <= 6;
        6: count <= 7;
        7: count <= 9;
        9: count <= 10;
        10: count <= 11;
        11: count <= 12;
        12: count <= 13;
        13: count <= 14;
        14: count <= 15;
        15: count <= 1; // Wrap around to 1 after 15
        default: count <= 1;  // Default case to start from 1
      endcase
    end
  end

endmodule

module tb_mod_15_counter;

reg clk;
  reg reset_n;
  wire [3:0] count;
  
  // Instantiate the mod-15 counter
  mod_15_counter uut (
    .clk(clk),
    .reset_n(reset_n),
    .count(count)
  );
  
  // Clock generation
  always #5 clk = ~clk;  // Clock period of 10 time units

initial begin
    // Initialize signals
    clk = 0;
    reset_n = 0;
    
    // Apply reset
    #10 reset_n = 1;
    
    // Let the simulation run for 200 time units
    #200 $stop;
  end
  
  // Monitor the output
  initial begin
    $monitor("Time: %0d, count: %0d", $time, count);
  end

endmodule

Devise different types of counters, for instance, a mod-15 counter that avoids 0, 3, 4, 8, and 5.

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