Disclosed embodiments select a proper hum frequency reference by utilizing one or more functional logic circuits within a cluster. The slowest logic circuit is determined, and an instance of that logic circuit is used in timing circuitry for the cluster. Multiple logic circuits with similar characteristics are incorporated into the timing circuit. Each cluster is interconnected to a second level timing circuit. Each cluster inputs timing information into the second level timing circuit. The second level timing circuit then determines when the next cycle, or tic, of the self-generated clock starts, and the process repeats, providing a self-generated clock signal.