def generate_timespec_buf(step = "1 ns", unit = "1 ps"):
    """
    Generate a timespec buffer given the input, if left empty fills in the
    default of 1ns/1ps

    Args:
        step (string): Timespec step
        unit (string): Unit of time step

    Returns:
        (string): buffer with the given timespec

    Raises:
        Nothing
    """
    buf  = "\n"
    buf += "`timescale %s/%s\n" % (step, unit)
    buf += "\n"
    return buf