Method and apparatus for arithmetic operation

An arithmetic logic unit for receiving 2M-bit data words X and Y and outputting a 4M-bit data word Z, characterized by comprising:

• a first register for storing bit-by-bit carries C resulting from additions;
• a second register for storing bit-by-bit sums S resulting from the additions;
• a third register for storing the data word Z;
• a first decoder for receiving and decoding high-order M bits of the data word X;
• a second decoder for receiving and decoding low-order M bits of the data word X;
• first and second selectors, each selecting either high- or low-order M bits of the data word Y;
• a first partial product generator for receiving output data of the first decoder and the first selector and generating partial products for a multiply-and-accumulate operation;
• a second partial product generator for receiving output data of the second decoder and the second selector and generating partial products for the multiply-and-accumulate operation;
• a first full adder for adding up the partial products generated by the first partial product generator;
• a second full adder for adding up the partial products generated by the second partial product generator;
• a data extender/shifter that receives output data of the first and second full adders and can perform data extension and data shifting on the data;
• a carry-propagation adder for receiving, and performing a carry-propagation addition on, the bit-by-bit carries C and the bit-by-bit sums S that have been stored in the first and second registers and outputting the result to the third register;
• a third selector for selectively outputting either the data stored in the third register or zero data;
• a fourth selector for selectively outputting either the output data of the carry-propagation adder or zero data;
• and
• a third full adder for receiving, and performing a full addition on, the output data of the data extender/shifter and the output data of the third and fourth selectors and for inputting the bit-by-bit carries C and the bit-by-bit sums S to the first and second registers, respectively.

An arithmetic logic unit for receiving data words X and Y and outputting a data word Z, where X and Y are each composed of a predetermined plural number of data units, each data unit having a predetermined number of bits, comprising:

• a register for storing and outputting a received data as a data word Z;
• a plurality of selectors, each selecting and outputting one of the plurality of data units of which the data word Y is made up;
• a plurality of multipliers respectively corresponding to the plurality of selectors, each of the plurality of multipliers multiplying together the data unit of the data word Y selected by the corresponding selector and a corresponding data unit of the plurality of data units of which the data word X is made up and outputting the result;
• a shifter for bit shifting each output of the plurality of multipliers according to necessity and outputting the result;
• and
• an adder for accumulating an output of the shifter or for adding an output of the shifter and an output of the register and for inputting the sum to the register,
• wherein a first operation, a second operation and a third operation are selectively performed,
• wherein the first operation is a repetition of a series of operation in which the respective selectors select a data unit that has not been selected by the respective selectors from the data units of the data word Y, the shifter bit shifts each output of the plurality of multipliers according to digit positions of the data unit in the data word X and the data unit in the data word Y which are input to each of the plurality of multipliers, and the adder performs the accumulation,
• wherein the second operation is performed in such a manner that each of the plurality of selectors selects a data unit of the data word Y which has the same digit position as that of the data unit of the data word X which is input to the corresponding multiplier of the plurality of multipliers and the adder performs the addition, and
• wherein the third operation is performed in such a manner that each of the plurality of selectors selects a data unit of the data word Y which has the same digit position as that of the data unit of the data word X which is input to the corresponding multiplier of the plurality of multipliers, the shifter bit shifts the outputs of the plurality of multipliers to respective digit positions not overlapping each other, and the adder performs the addition.