| 摘要 |
A I/O controller which is connected to a plurality of I/O units and one spare I/O unit, controls a plurality of I/O units based on a command from a master unit, and allows a spare I/O unit to be used in place of an I/O unit where an abnormality is found, when an abnormality is found in any of a plurality of I/O units. This I/O controller gives a decision about normality at a time interval not in use for an operation when no command from a master unit (10) is being processed, after selecting I/O units (30) or a spare I/O unit (31). When it gives a decision of abnormality, the controller stores information about the abnormality in preventive maintenance information storage register (25) as preventive maintenance information.
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