Waveform data generation apparatus

A waveform data generation apparatus for generating sine wave data and cosine wave data according to an angle change within a range 0-360 degrees, said apparatus comprising:

• first storage means for storing first sine wave data or first cosine wave data in either of the angular sections on both sides of a zero-crossing point of a sine wave or a cosine wave, each of said angular sections being 45 degrees of an angular range which is defined as one of eight sections equally divided between 0 and 360 degrees on the basis of 0 degree;
• second storage means for storing second sine wave data or second cosine wave data in an angular section adjacent to the angular section on which the data stored in said first storage means exists, under a condition that the first sine wave data or the first cosine wave data and the second sine wave data or the second cosine wave data include 0 and a maximum or a minimum thereof;
• pulse counting means for counting pulses indicating an angular change and outputting the binary counted value corresponding to an angle within a range 0-360 DEGREES, said pulse counting means outputting a first counted value to be reset at every angular section and a second counted value being a counted value of a bit carried-up at every reset of the first counted value at every 45 degrees;
• read address selection means including angle inversion means for performing an angle inversion of the first counted value on the basis of 45 degrees and first selection means for receiving a first inverted counted value, which is angle-inverted by said angle inversion means, and the first counted value and outputting the received two counted values as a reading address of said first and said second storage means according to the least significant bit of the second counted value;
• data selection means including second selection means for receiving the sine wave data and the cosine wave data, which are read out from said first and said second storage means in response to the address output from said read address selection means, and selecting and outputting the sine wave data and the cosine wave data according to the states of two bits of the least significant bit of the second counted value and a higher order bit adjacent to the least significant bit;
• and
• polarity processing means including first polarity conversion means for converting a polarity of the sine wave data output from said second selection means, second polarity conversion means for converting a polarity of the cosine wave data output from said second selection means, and third selection means for receiving the sine wave data output from said second selection means, the sine wave data having a polarity converted by said first polarity conversion means, the cosine wave data output from said second selection means, and the cosine wave data having a polarity converted by said second polarity conversion means, and selecting and outputting the sine wave data and the cosine wave data, the polarities of both being processed according to the states of two bits of one and two higher order bits next to the largest significant bit.