How Often Does Gen AI (and not even chatGPT) Get It Right First Time and For FREE??? (Google) - veriloga clock selector

Even Andrea is proud

This is not something that takes two clocks and puts the "new" one out in a "safe" way (you have to wait till the active clock goes LO before you switch to the other one)

This is a module that has settings for the two frequencies and does the update in a smart way so you never see a glitch or a very long period from waiting to be "safe".

Blew me away that Google gave me this for free

// prompt : veriloga module outputs one of two clock frequencies based on select input
`include "disciplines.vams"
`include "constants.vams"

// Module to generate one of two clock frequencies
module dual_freq_clock (
    clk_out,
    select
);

    output clk_out;
    input select;

    electrical clk_out, select;

    // Parameters for clock frequencies and transitions
    parameter real freq1 = 100M; // First frequency (100 MHz)
    parameter real freq2 = 50M;  // Second frequency (50 MHz)
    parameter real t_rise = 100p; // Rise time
    parameter real t_fall = 100p; // Fall time
    parameter real vdd = 1.8;   // Supply voltage
    parameter real vss = 0.0;   // Ground voltage
    parameter real v_thresh = (vdd + vss) / 2; // Threshold for the select signal

    // Internal variables
    real period;
    real toggle_time;
    integer toggle;

    analog begin
        // The `if-else` statement checks the value of the `select` input
        // at each time step.
        if (V(select) > v_thresh) begin
            // If select is high, use the first frequency.
            period = 1 / freq1;
        end else begin
            // If select is low, use the second frequency.
            period = 1 / freq2;
        end

        // The `cross` function is used to schedule events based on time.
        @(initial_step) begin
            toggle = 0;
            toggle_time = 0;
        end

        // Schedule the next toggle event.
        @(timer(toggle_time)) begin
            toggle = 1 - toggle; // Toggle the state (0 -> 1 or 1 -> 0)
            toggle_time = $abstime + (period / 2); // Schedule the next toggle for half a period later
        end

        // Drive the output voltage based on the `toggle` variable.
        V(clk_out) <+ transition(toggle * (vdd - vss) + vss, 0, t_rise, t_fall);
    end

endmodule

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