Abstract: The present invention relates to a ROM division method for reducing the size of a ROM in a direct digital frequency synthesizer (DDFS), which is used to synthesize a frequency in a communication system requiring fast frequency conversion. A ROM consuming most energy in the system, a modified Nicholas architecture is brought forth to reduce the size of ROM. In this modified Nicholas architecture, a ROM is divided into coarse ROM and fine ROM to convert phase to sine value. The present invention divides the coarse ROM and the fine ROM into quantized ROM and error ROM respectively. Then, value stored in each ROM is segmented in certain intervals and the minimum quantized value in each of the section is stored in the quantized ROM, while the difference between the original ROM value and the quantized ROM value is stored in the error ROM. This way, the size of a ROM can be reduced. Phase value inputted in a DDFS, a sine value is calculated by adding the four ROM values, i.e.

Abstract: The present invention relates to a ROM division method for reducing the size of a ROM in a direct digital frequency synthesizer (DDFS), which is used to synthesize a frequency in a communication system requiring fast frequency conversion. A ROM consuming most energy in the system, a modified Nicholas architecture is brought forth to reduce the size of ROM. In this modified Nicholas architecture, a ROM is divided into coarse ROM and fine ROM to convert phase to sine value. The present invention divides the coarse ROM and the fine ROM into quantized ROM and error ROM respectively. Then, value stored in each ROM is segmented in certain intervals and the minimum quantized value in each of the section is stored in the quantized ROM, while the difference between the original ROM value and the quantized ROM value is stored in the error ROM. This way, the size of a ROM can be reduced. Phase value inputted in a DDFS, a sine value is calculated by adding the four ROM values, i.e.

Abstract: Disclosed is an improved discrete cosine transform processor comprising an input unit for receiving image data to be processed, a storage unit for previously storing a result of a multiplication and accumulation calculation effected beforehand with respect to image input data and transform matrix components so that the same value is read from the same read line; a decoding unit for selecting the read line, in which each bit value of the image input data composed of a plurality of bits serves as a piece of address data; an accumulation unit for accumulating the data read from the storage unit and an output unit for outputting a result of the accumulation processing as output data. The storage unit uses the common data in common when effecting the multiplication and accumulation calculation, and, hence, a storage capacity is reduced, thereby making it possible to decrease a chip area.

Abstract: A discrete cosine transform processor for executing discrete cosine transform calculations in both forward and inverse directions on the basis of previously stored product addition data has a memory having a first memory section for storing product addition calculation data for the forward direction transformation and a second memory section for storing product addition calculation data for the inverse direction transformation other than data in common to those stored in the first memory section; and sign inverter for inverting signs of the data used in common for the inverse direction transformation, among the data stored in the first memory section. The memory preferably includes first memory for storing product addition data corresponding to even-order coefficients and second memory for storing product addition data corresponding to odd-order coefficients; and only the second memory stores data used in common for both the forward and inverse direction transformations in the first memory thereof.