| 摘要 |
<p>A floating-point processor for performing addition and subtraction of two floating-point numbers, which is provided with a carry saving adder-subtracter for generating carry data and sum data by performing addition and subtraction of a first fixed-point part of the floating-point number having a greater exponent part and a second fixed-point part, which is aligned with the first fixed-point part by being shifted right, of the other floating-point number having a smaller exponent part by saving a carry, a rounding-carry generating circuit for generating a first rounding-carry, of which the value in case of rounding the result of addition or subtraction between the first and second fixed-point parts to a higher order digit is in agreement with the value in case of rounding the result of addition or subtraction between the first and second fixed-point parts to a lower order digit, from a rounding-mode signal indicating the direction, in which a result of addition or subtraction between the first and second fixed-point parts is rounded, and low-order digits of the first and second fixed-point parts and for generating a second rounding-carry in each of the cases of rounding the result of addition or subtraction between the first and second fixed-point parts to a higher order digit and of rounding the result of addition or subtraction between the first and second fixed-point parts to a lower order digit, an adder-subtracter for outputting a first result of addition or subtraction between data, which is obtained by adding the first rounding-carry to low-order digits of the carry data, and the sum data and for outputting a second result of adding 1 to or subtracting 1 from the first result and an inversion circuit for outputting a logical inversion of all digits of the second result, wherein one of the first result, the second result and an output of the inversion circuit is selected and outputted on the basis of high-order digits of the first and second results and the second rounding-carry. <IMAGE></p> |
