Digital waveform generating apparatus

Abstract

A digital waveform generating apparatus includes a key assignor selecting a frequency of a signal to be generated, a number-setting circuit for generating a first data word corresponding to the selected frequency, a first memory for storing said first data word, a second memory for storing a second data word, an accumulator for accumulating the first data word onto the second data word stored in the second memory, so that the second data word stored in the second memory after accumulating represents the sum of the second data word immediately prior thereto added with said first data word, a waveform memory, preferably an ROM, for storing predetermined waveform data and for generating a waveform data output signal, and a control circuit for controlling such accumulating and progressively addressing the waveform memory in accordance with the stored second data word at the time of a timing signal. Preferably, the number-setting circuit generates a plurality of the first data words corresponding to at least one corresponding frequency, the first and second memories have a plurality of channels storing the first data word and the second data words to be added with the first data words, and the control circuit operates in a time-sharing fashion. To avoid folded errors in the output signal, the waveform memory can include a plurality of data banks each storing waveform data corresponding to a predetermined portion of the frequency range of the apparatus, and the control circuit operates to select an appropriate data bank corresponding to the selected frequency.