DRV2604: DRV2604 Stopping Waveform Playback

Part Number: DRV2604

What would be the recommended way to immediately stop a DRV2604 waveform executing from RAM, or to at least verify that no waveform is currently running, in order to update the program data? I've tried clearing the GO bit, but this doesn't seem to stop the currently executing waveform.

As would be expected, if I update the program data while a waveform is executing, strange things happen.

Thanks!