Integrated central processor for electronic organ

TLDR: In this article, a central processor for an electronic organ in the form of a single, forty pin integrated circuit chip employing multiplexed technology and trinary and tri-level inputs to obtain maximum usage from each pin.

Abstract: A central processor for an electronic organ in the form of a single, forty pin integrated circuit chip employing multiplexed technology and trinary and tri-level inputs to obtain maximum usage from each pin. The solo manual keys, chord keys, rhythm pattern switches and other control functions are multiplexed externally of the chip, fed into the chip as a time division multiplexed four bit byte over four pins, and demultiplexed internally of the chip. The solo manual information is multiplexed internally of the chip to form a single serial data stream, is combined with solo fill note data generated within the chip and then brought out over a single pin for external demultiplexing. The twelve tones of a musical octave are brought into the chip over twelve pins together with various static control signals, are decoded by tri-level decoders internally of the chip, and then utilized to generate the tones of the chords, also internally of the chip. Chord tone generation is accomplished by selecting the musical fifth tone in an internal ROM, dividing this tone by a factor of three to produce the fundamental and generating the third and seventh tones also through the use of internal ROMs. Keying of the chord tones is accomplished by internal digital sustain keyers which provide an output over a single pin. There is also provided internally of the chip the capability for producing bass patterns, note patterns and rhythm percussion patterns. By suitable controls, the chip may be adapted for use in a large organ configuration, where various of the timing controls are generated externally, and in a small organ configuration, where these controls are generated internally of the chip.