| 摘要 |
PURPOSE:To attain high speed arithmetic by constituting two systems of carry propagation circuits corresponding to the presence of a carry in advance. CONSTITUTION:The carry circuit having plural carry propagating circuits of one block consists of the 1st carry circuit 20', the 2nd carry circuit 20a connected via a carry propagation control circuit 27a to the circuit 20a, and the 3rd carry circuit 20b through switches 25b, 26b connected via carry propagation control switches 25a, 26a and a carry propagation control circuit 27b to the circuit 20a. Each carry circuit starts the calculation of a sum signal and a carry signal at the same time as the start of each arithmetic by using the two systems of the propagating paths based on the input circuit corresponding to the presence of the value of carry from the pre-stage in advance. Thus, the block of the next stage is calculated excessively by the time required for the control time of the switches 25(25a, 25b) and 26(26a, 26b) to the preceding block. |
