To provide a highly reliable logging system for protecting the data structure of an external storage medium such as a compact flash even if power source interruption occurs in any timing, and for restoring log data prior to the power source interruption.
The logging system is provided with: a log data management region installed in a quickly accessible non-volatile memory such as an SRAM. Furthermore, with a low voltage detection circuit for securing an access time of the management region, and a flag value is confirmed before the write-in of the management area, so that power source interruption can be prevented from occurring during data management region write-in, and so that data structure breakdown in the external recording medium can be prevented. Furthermore, the logging system is provided with a memory block in the non-volatile memory, and log data are written in both the memory block and the external recording medium, and log data are compared and checked at a restart after the power source interruption, so that it is possible to maintain the matching of the log data and to improve reliability.
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ONO KOJI
OKI YOSUKE
