| 摘要 |
PURPOSE:To use properly a multiplication mode through a single multiplying device by forming a multiplying device with four (8X8)-bit ROM type multipliers and changing the multiplication bit length to (16X16) bits or (8X8) bits. CONSTITUTION:A multiplicand X and a multiplier Y are supplied through input terminals 11 and 12 respectively and both X and Y and the product output P are supplied and delivered in time division for each 8 bits and 16 bits respec tively. At the same time, multipliers 19-22 which perform the (8-8)-bit multipli cation are used for operation of (16-16) bits. In this case, both X and Y are decomposed into upper 8-bit X1 and Y1 and low 8-bit X0 and Y0. Thus, a product is obtained. In other words, the product output P=X.Y=(X1.2<8>+X0)(Y1.2<8>+ Y0)=X1.Y1.2<16>+X1.Y0.2<8>+X0.Y1.2<-8>+X0.Y0 is satisfied. While the multiplica tion of X1.Y1, X1.Y0, X0.Y1 and X0.Y1 and X0.Y0 are all carried out with (8X8) bits and can be calculated by multipliers 19-22 respectively. |
