verilog pll

Verilog is a hardware description language (HDL) used for modeling and designing digital systems. A Phase-Locked Loop (PLL) is a common component used in digital circuit design, particularly in clock generation and frequency synthesis.

In Verilog, you can describe a PLL using behavioral, dataflow, or structural modeling styles. Here's a simple example of a behavioral model for a PLL:

module PLL (
  input wire clk_in,
  input wire reset,
  output wire pll_out
);

  reg phase_locked;
  reg [7:0] counter;

  always @(posedge clk_in or posedge reset) begin
    if (reset)
      counter <= 8'b00000000;
    else if (counter == 8'b11111111)
      counter <= 8'b00000000;
    else
      counter <= counter + 1;
  
    phase_locked <= (counter == 8'b11000000);
    pll_out <= phase_locked ? ~pll_out : pll_out;
  end

endmodule

This example demonstrates a basic PLL that generates an output clock (`pll_out`) by dividing the input clock (`clk_in`). The `counter` variable is used to divide the frequency, and once it reaches a specific value (`8'b11000000` in this case), the PLL locks to the input clock.

Please note that this is just a simple example, and real-world PLL designs may involve more complex logic and additional components.