| 摘要 |
PURPOSE:To perform the decimal multiplication at a high speed by producing a desired multiple in the minimum cycle number with use of the multiple registered at present in case a multiple which is not registered in a multiple table yet and carrying out the multiplication. CONSTITUTION:The number which is segmented for each decimal digit out of a multiplier (or multiplicand) register 4 via a shifter 5 and a register flag 2 are decoded by a decoder 3. Then the corresponding multiple is read out of a multiple table 1 and added with the value of an intermediate product holding register 7 via a decimal ALU 6 for acquisition of the new value (multiplicated intermediate value) in case it is decided that said segmented value and the flag 2 are registered in the table 1. In case no registration is decided for said value and the flag 2, the optimum multiple combination is obtained for production of a desired multiple via the flag 2. Then the multiple is read out of the table 1 based on said combination and the desired multiple is produced by the ALU 6 and registered. The multiple thus obtained is added with the value of the register 7 via the ALU 6 for acquisition of the new value (multiplicated intermediate value). Thus the processing speed is improved for a decimal multiplication instruction. |
