How can I control the envelope of the output?

There are two methods for enveloping short output bursts: automatic output shift keying (OSK), and manual OSK. In automatic mode, the user can program a maximum amplitude scale factor (≤=1). When the OSK pin is brought high, the part will ramp from a scale factor of zero to the set value in an interval defined by the value in the ramp rate register. When the pin is brought low, the amplitude is ramped back down at the same rate to zero. In manual mode, the user can write and update scale factors to increase or decrease the amplitude during the burst. The user must assure that the part can accept data at the required update rate via its serial or parallel I/O interface.