Systems, methods, and apparatus for generating a clock signal using re-timer circuitry, including receiving an input data signal transmitted without a reference clock signal; comparing the input data signal with a re-timer clock signal to determine a frequency difference between the input data signal and the re-timer clock signal; determining a data rate of the input data signal based on the frequency difference between the input data signal and the re-timer clock signal; and generating, based on the data rate of the input data signal, a control signal for adjusting a frequency of the re-timer clock signal to frequency-lock the re-timer clock signal with the input data signal.