| 摘要 |
PURPOSE:To accurately recognize whether the failure in an access is caused by a power unit or by an I/O device by providing a service interruption detection means for detecting the service interruption of the power unit and a flip flop which is set when the return of the power source is detected by the service interruption detection means. CONSTITUTION:The service interruption detection means 74 in a repeating installation 7 detects the service interruption of a second power unit 8 and also it sets (the state of '1') the flip flop 75 at the time of detecting the return of the power source. A CPU 1 reads the state of the flip flop 75 when the access to the I/O device fails and decides whether the state of the flip flop 75 is '1' or '0'. Now if the state is '1', the CPU 1 recognizes that it is the failure in access caused by the service interruption of the second power unit 8 and at the same time resets the flip flop 75. If the state of the flip flop 75 is '0', the CPU recognizes the failure in access caused by the fault of the I/O device and executes the processing of errors in the I/O device which is previously prescribed in a system.
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