| 摘要 |
PURPOSE:To attain the high speed of an arithmetic operation by dividing a full adder with a carry look ahead into the high-order side of the number of the power of 2, and the low-order side of the edge number, and completing the arithmetic operation of the low-order side until the arithmetic operation of the high-order side is started. CONSTITUTION:A number to be operated is used as the complement of 2, and a multiplication is operated by using the algorithm of a booth. A full adder CLA with a carry look ahead is used as the adder which communicates the carry at a final stage to a digit direction, and it is divided into a high-order side CLA1 and a low-order CLA2. Then, the high-order side is defined as the number of digits corresponding to the number of the power of 2, the low-order side is defined as the number of digits corresponding to the number of digits of the edge number overflowing from this, and the carry of the low-order side CLA2 is inputted to the high-order side CLA1. An input to the low-order side CLA2 is early decided, and then the arithmetic operation of the low-order side CLA2 is completed at the time of starting the arithmetic operation of the high-order side CLA1, and the carry of this result is inputted to the high-order side CLA1. Thus, the entire arithmetic operation can be decided only by the operation time of the high-order side CLA1 regardless of the operation time at the low-order side, so that the operation time can be shortened. |
