| 摘要 |
PURPOSE:To give more meaning to respective bits of an instruction register without varying the number of bits of a microprogram memory, and to obtain a processor of simple constitution, by providing an instruction register modifying circuit and an instruction register modifying register. CONSTITUTION:According to addresses generated by a microprogram sequencer 1, instructions in a microprogram memory 2 are set in an instruction register 3. According to the formats of instructions from this register 3, an instruction register modifying circuit 8 decides on the meaning of each bit of the register 3 to a control circuit on the basis of the contents of an instruction register modifying register 7 to write the meaning in each bit. The interface 4 between an arithmetic part and an external circuit is controlled by the output of the circuit 8, and the external circuit 6 is controlled by its output. Thus, each bit of the register is given more meaning without varying the number of bits of the memory 2, simplifying the constitution of the processor. |
