| 摘要 |
PURPOSE:To substitute a storage part for a faulty ROM without stopping devices, by reading instructions from the second storage part when register address information, where a specific address of a program storage ROM is registered, coincides with read address information. CONSTITUTION:Controlling micro mu programs are stored in the first storage ROM1, and substitutional instructions for mu instructions stored in optional addresses of the ROM1 are stored in an address area other than that of the ROM1 on the second storage WCS3. Address information from an address controlling circuit 2 is supplied to the ROM1, the WCS2, and an address comparing circuit 4. Information of a specific address of the ROM1 is registered in the circuit 4, and this registered address information is compared with address information from the circuit 2; and when they coincide with each other, a coincidence signal 8 is supplied form the circuit 4 to a mu instruction register 6, an instruction discrimination controlling circuit 7, and the circuit 2. Simultaneously, the address of the substitutional instruction in the WCS3 is outputted to the circuit 2 from a substitutional address information register part 5, and the substitutional instruction of the WCS3 is outputted to the circuit 7 through the register 6. |
