| 摘要 |
PURPOSE:To decrease the number of microinstructions and to reduce the capacity of a microinstruction memory part by designating the change of a field to the microinstructions having similar descriptions with those fields excepting for a specific one. CONSTITUTION:An instruction decoding part 1 decodes a microinstruction A and outputs the head address B of a series of microinstructions that describe the processing of the instruction A together with the field information E. A field changing circuit 3 inspects the specific field F of the microinstruction outputted from a microinstruction memory part 2 which stores a microinstruction C. Then the circuit 3 changes the relevant field based on the field information outputted from the part 1 if the field change is designated and delivers the changed field. If no field change is designated, the relevant field is outputted as it is with no change. A microinstruction register 4 stores the outputs of both the part 2 and the circuit 3 and outputs a changed microinstruction through an output 5. In such a constitution, just a single microinstruction is enough for expression and therefore the capacity of the part 2 is reduced.
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