HD6432345 Datasheet, PDF (596/907 Pages) Hitachi Semiconductor – H8S/2345 F-ZTAT Hardware Manual

The error protect function has no effect on illegal operations unrelated to the setting conditions for
the FLER bit. Also, if a significant amount of time has elapsed before the transition to the protect
status, there is a possibility that the data in flash memory may already have become corrupted.
Consequently, this function is not able to provide complete protection against corruption of the
data in flash memory.
For this reason, it is necessary to run program and erase algorithms correctly while flash write
enable (FWE) is being applied and to monitor the internal operation of the microcomputer for
abnormalities using a watchdog timer, or the like, in order to prevent illegal operations of the sort
mentioned above. Also, at the point when the transition is made to the protect mode, in some cases
the flash memory may be in an erroneously programmed or erased status, or the programming or
erasing may be incomplete due to a forced shutdown. In such a case, make sure to force a recovery
(program rewrite) using the boot mode. Note that there may still be cases in which boot mode
cannot be started normally due to excessive programming or erasing of the flash memory.
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