| 摘要 |
PURPOSE:To quicken detection of overflow and to shorten a time for arithmetic by overlapping fixed point arithmetic and detection of overflow of the result of operation. CONSTITUTION:Operation in the case there is carry input from low-order digit is made by an arithmetic unit 6 of carry input 1 of an arithmetic unit, and arithmetic in the case of there is no carry input is made by an arithmetic unit 7 of carry input '0'. The result of operation of arithmetic units 6, 7 is selected by a selector circuit 8 basing on the presence of a carry input, and stored in an arithmetic result storing register 9. Selective operation of the circuit 8 is made in parallel, and the results of operation of aritmetic units 6, 7 are led to respective overflow detecting circuit 11, 12, and the result of detection of overflow detected by respective circuit 10, 11 is selected by a selector circuit 12 basing on the presence of the carry input. The circuit 8, 12 are controlled by a arithmetic indication storing FF 5 that makes an arithmetic indication signal 100 input. Output of the circuit 12 is stored in a result of overflow detection storing FF 13, and the time for operation is shortened. |
