PURPOSE: To decrease the hardward amount of the titled circuit by using a code bit of input/output data of an operating circuit to detect the overflow of the result of operation and correction of its output data.
CONSTITUTION: Signals Ain, Bin are inputted to an adder circuit 401 and the result of operation Cout is obtained. Since a handled signal is represented by 2's complement, and when the MSB is at L, the signal is a positive number and when at H, the signal is a negative number, then a selector signal 403 of a data selector 402 is formed as shown in the figure. In case of overflow, an overflow detection signal is generated and required data is selected at the same time. That is, when both P, N are at L, the selector 402 selects the operation result Cout. On the other hand, when the P of the signal 403 is at L and the N is at H, black clip data B is selected, and when the P is at H and the N is at L, white clip data W is selected. Through the circuit constitution above, since no magnitude comparator is used, the number of components is decreased.
MORIMURA ATSUSHI
FUJIMOTO MAKOTO
KITAMURA YOSHINORI
