An aspect includes a direct digital synthesis system including a waveform generator with a waveform memory operable to store a plurality of waveform vectors and output a selected waveform vector. The direct digital synthesis system also includes a digital-to-analog converter operable to convert the selected waveform vector from a digital value to an analog signal responsive to a reference clock. The direct digital synthesis system further includes a controller operable to maintain phase continuity of the analog signal when an output of the analog signal is interrupted and restored.