| 摘要 |
PURPOSE:To reduce a circuit scale by disposing an inversion circuit inverting respective bits of a subtrahend and executing the complementary conversion of '1', and full adders which set the carry output by means of the addition of the output value and a minuend to be a self carry input. CONSTITUTION:The inversion circuit 1 inverts respective bits of the subtrahend, executes complementary conversion of '1', and the full adders 2 add the output value of the circuit 1 and the minuend and set the carry output by addition to be the self carry input. An inversion selection circuit 3 outputs the output addition value of the adder 2 as an output when the carry output is '1', and inverts respective bits of the output addition value, inversely converts the comple ment of '1', and outputs it as a difference when the carry output is '0'. Name ly, 'end around carry' can be realized by setting the carry output of the adder 2 to be the self carry input since subtraction is attained by the complement conversion of '1' of the subtrahend. |
