| 摘要 |
PURPOSE:To shorten the executing time of a soft instruction and to exclude a control memory by using hardware to decide a direct addition/subtraction as well as an output code. CONSTITUTION:The 1st and 2nd operators 7 and 8 are provided, and an addition/subtraction instruction (addition 0, subtraction 1) given from outside is held at a register 3. At the same time, the 1st and 2nd operand codes are held at registers 5 and 4 respectively. Based on the combination b0 of these registers, an input carry and an action mode of the operator 7 are decided. Based on these action mode and carry of the operator 7, the outputs of operators 7 and 8 and the arithmetic result code are selected respectively. Thus it is possible to decide both a direct arithmetic mode and an output code by means of hardware. |
