| 摘要 |
PURPOSE:To redefine easily an instruction code of an undefined instruction by executing the wiring of a decoding circuit so that the undefined instruction discriminates the instruction code as an instruction of two or more step numbers. CONSTITUTION:In case an instruction of an instruction register 1 is an undefined instruction, an instruction classification decoder 3 is brought to wiring so that a control line 5 is turned on as an instruction which requires two or more microsteps. In case when a redefinition is executed so that an instruction code of this undefined instruction is used as an additional instruction, a micro- instruction which is read out by the instruction code is redefined by loading again a control memory 8 so that it goes to, for instance, a jump instruction to the micro-instruction of an inlet of a microprogram used for the additional instruction. In that case, it is unnecessary to change the wiring of the instruction classification decoder 3, therefore, the redefining processing is executed easily. |
