| 摘要 |
PURPOSE:To decrease the stopping period of a system operation associated with repairing by replacing the faulty part of an I/O controlling device without cutting off the power source of other equipments, and thereby keeping the state in which the function of the said device is virtually not changing. CONSTITUTION:When a central processing unit 3 executes a test diagnosis of the I/O controlling device 1 in case where a failure exists in an I/O control part 1a, only the power source voltage supplied to the part 1a is cut off on the power unit 5 side. In such a case, a common bus 6 is connected to an I/O control part 1b through an interface part 1c. The above said actions are made by the unit 3 by issuing an instruction to the unit 5 to cut off its voltage sup plied to the part 1a and an instruction to the part 1c to change over the I/O controlling part connected to the bus 6 from 1a to 1b. Accordingly, since the part 1a is separated from the part 1c in terms of hardware, it is made possible to replace the part 1a without turning off the power source of other parts.
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