You are an expert Verilog hardware designer working on a complete FPGA or ASIC project. You are given the full source code of a Verilog project. One of the modules in the project is incomplete — its implementation is missing and marked with:

// >>> Module Implementation Begin

// <<< Module Implementation End

Your task is to complete the missing implementation so that the entire project functions correctly. You must infer what the missing module or logic is supposed to do by analyzing the rest of the codebase: module names, signal connections, instantiations, comments, and usage patterns.

Follow these rules:

1. Only generate Verilog code to go between the `// >>> Module Implementation Begin` and `// <<< Module Implementation End` comments.
2. Use Verilog-2001 syntax. Ensure the code is synthesizable.
3. Assume the goal is a working, integrated hardware design — your code must make the whole system function as intended.
4. Analyze the naming, I/O ports, and how the module is instantiated or used in other parts of the project.
5. Implement correct behavior based on design context. Do not guess randomly — reason it out.
6. Avoid vendor-specific features unless explicitly required.
7. Do not output comments, explanation, or anything outside the required code region unless explicitly asked.

Your output should contain **only the Verilog code** that fits inside the marked region.

/*
 * Copyright (c) 2024 Evan & Catherine
 * SPDX-License-Identifier: Apache-2.0
 */

`default_nettype none

module tt_um_program_counter_top_level (
    input  wire [7:0] ui_in,    // Dedicated inputs
    output wire [7:0] uo_out,   // Dedicated outputs
    input  wire [7:0] uio_in,   // IOs: Input path
    output wire [7:0] uio_out,  // IOs: Output path
    output wire [7:0] uio_oe,   // IOs: Enable path (active high: 0=input, 1=output)
    input  wire       ena,      // always 1 when the design is powered, so you can ignore it
    input  wire       clk,      // clock
    input  wire       rst_n     // reset_n - low to reset
);
// >>> Module Implementation Begin

// <<< Module Implementation End
endmodule



module j_k_logic (
  input pclr,
  input lp,
  input cp,
  input bn,
  input a,
  output j,
  output k
);
  wire plp_cp_a;
  assign plp_cp_a = ~lp & cp & a;

  assign j = (pclr & plp_cp_a) | (pclr & lp & bn);
  assign k = (~pclr) | (plp_cp_a) | (lp & ~bn);
endmodule

module JK_flip_flop(input j, input k, input clk, output reg q);

  always @ (posedge clk)
    case ({j,k})
      2'b00: q <= q;
      2'b01: q <= 0;
      2'b10: q <= 1;
      2'b11: q <= ~q;
    endcase
endmodule

module set_counter_bit(input CLR_n, input Lp, input Cp, input b, input A, input CLK, output S);

  wire j, k;
  j_k_logic jk_logic(CLR_n, Lp, Cp, b, A, j, k);
  JK_flip_flop flip_flop(j, k, CLK, S);

endmodule

module ProgramCounter (
  input wire[3:0] bits_in,
  output wire [3:0] bits_out,
  input wire clk,
  input wire clr_n,
  input wire lp,
  input wire cp,
  input wire ep
);
  wire[3:0] counter;
  set_counter_bit set_bit_0(clr_n, lp, cp, bits_in[0], 1'b1, clk, counter[0]);
  set_counter_bit set_bit_1(clr_n, lp, cp, bits_in[1], (counter[0]), clk, counter[1]);
  set_counter_bit set_bit_2(clr_n, lp, cp, bits_in[2], (counter[0] & counter[1]), clk, counter[2]);
  set_counter_bit set_bit_3(clr_n, lp, cp, bits_in[3], (counter[0] & counter[1] & counter[2]), clk, counter[3]);

  reg enable;
  always @ (posedge clk) enable <= ep;
  assign bits_out = enable ? counter : 4'bZZZZ;
endmodule


Reference solution:
rtl/generated.v: 
  ProgramCounter pc(
    ui_in[7:4],
    uo_out[3:0],
    clk,
    rst_n,
    ui_in[0],
    ui_in[1],
    ui_in[2]
  );

  // All output pins must be assigned. If not used, assign to 0.
  assign uio_out = 0;
  assign uio_oe  = 0;
  assign uo_out[7:4] = 0;
  // List all unused inputs to prevent warnings
  wire _unused = &{ena, ui_in[3], uio_in, 1'b0};