| 摘要 |
PURPOSE:To substitute a storage part for a faulty ROM easily, by supplying substitutional address information, which is read out from a substitutional address registering means, to a substitutional instruction storage part in accordance with information indicating the substitution of the instruction in a specific address of the ROM. CONSTITUTION:Controlling micro mu instructions are stored in a ROM1, and a substitutional instruction for the instruction in a specific address of the ROM1 is allocated to another address area and is stored in a WCS3. Specific address information of the ROM1 from an address controlling circuit 2 is read out by an index memory 51 and the ROM1, and the instruction in a specific address is outputted from the ROM1 to a mu instruction register 6. Substitution indicating information is read out from the memory 51 and is outputted to an index number discriminating circuit 52. The circuit 52 decodes this information and sends a designating signal to a substitutional address register part 4, and an address of the WCS3 is designated by the register part 4 to read out a substitutional instruction, and this instruction is outputted to the register 6. An address update inhibiting signal 10 and an instruction inhibiting signal 11 are outputted to inhibit the circuit 2 from reading out the instruction in the next address and to make instructions from the ROM1 ineffective in an instruction discrimination controlling circuit 7. |
