A numerically controlled oscillator includes a phase accumulator configured to output a phase word, a clock configured to periodically output a clock signal in accordance with a delay interval, and a clock controller configured to adjust the delay interval. The phase accumulator is configured to output a new phase word in response to receiving the clock signal. An example method includes receiving a plurality of frequency control words, calculating a delay interval, accumulating the frequency control words in accordance with the delay interval to generate a phase word, and converting the phase word to a waveform.