ranger@ecsvax.UUCP (Rick N. Fincher) (12/17/86)
Apple IIGS: Sound Logic To support sound, the Apple IIGS has the Apple IIGS Sound General Logic Unit, an Ensoniq sound chip, 64K of dedicated sound RAM, and associated circuitry. Sound General Logic Unit The Apple IIGS Sound General Logic Unit (Sound GLU) provides an interface between the Ensoniq sound chip and the remainder of the Apple IIGS logic system. The Sound GLU permits the Ensoniq chip to run independently of the Mega II chip. The Sound GLU contains a control register, data register, and address pointer. Bits within the control register determine the system volume level and control the flow of information between the Ensoniq chip and Sound RAM. The data register and address pointer are used to transfer information to and from the dedicated 64K of Sound RAM to the Ensoniq digital oscillator chip. Ensoniq Digital Oscillator Chip The Ensoniq chip contains 32 oscillators, two of which are reserved for use by the Apple IIGS itself. The remaining 30 oscillators are used in pairs to produce 15 sound voices. Each oscillator uses seven DOC registers which contain such parameters as the frequency rate at which the oscillator steps through its wavetable, the size and starting address of the wavetable, data obtained from the wavetable, and the volume and mode of the oscillator. Sound RAM 64K of RAM is provided for the exclusive use of the Ensoniq DOC. It contains wavetables, which are digitized waveforms, for each of the oscillators. Apple Technical Communications