MIDI Controlled Sample-Based Synthesizer
Amir Hirsch and Andrew Leiserson
Overview | Communication | Master Control Unit | Sound Generation Unit | Mixer
The Master Control Unit processes user input from the PS/2 keyboard and lab kit switches and control/note data from the MIDI interface. The control unit issues commands to the display and the SGU via the control bus.The bulk of computation occurs in the Sound Generation Unit (SGU). The SGU receives specially-formatted control messages on the control bus instructing it to start or end note playback and notifying it of changes to filter parameters.
Generated audio from the SGU is passed via a special audio bus. The audio bus could be generalized to allow transmission of audio to/from multiple modules such as a system effects processor, mixer, or resampler that records system output to sample memory. The audio bus receiver decodes samples from the audio bus and passes them to the SGU input on the mixer. The SGU audio is mixed with the input audio and the audio signal coming direct from the memory controller. Passing the input audio through allows the user to preview the sound that will be recorded into sample memory without reconnecting the speakers or using an external mixer. The sample playback channel allows recorded samples to be previewed directly.
The system architecture is shown below.
