// ==========================================================
// Helper: FTW function (compile-time or runtime call)
//   FTW = round( f_hz * 2^PHASE_BITS / FS_HZ )
// Notes:
// - Accepts integer Hz.
// - Uses 64-bit math to avoid overflow for typical params.
// - Can be called from a testbench or combinational logic that
//   prepares 'ftw_in' before asserting 'ftw_we'.
// Example:
//   initial begin
//     #1;
//     $display("FTW 1kHz = 0x%08x", ftw_from_hz(1000));
//   end
// ==========================================================
function [31:0] ftw_from_hz;
  input integer f_hz;
  input integer phase_bits;
  input integer fs_hz;
  reg   [63:0] numer;
  begin
    numer       = ((64'd1 << phase_bits) * f_hz) + (fs_hz/2);
    ftw_from_hz = numer / fs_hz;
  end
endfunction