Notes - Renesas F-ZTAT H8 Series Hardware Manual

Section 12 Watchdog Timer
12.6

Notes

This chip incorporates an WDT. The timer counter value of the on-chip WDT is not rewritten,
even if a system crash occurs. If an overflow occurs, a reset signal is generated and the chip is
reset.
However, if the following three events occur due to a CPU overrun, for example, the above
operations cannot be guaranteed since the WDT and the CPU are incorporated in the same chip.
• When the internal I/O registers related to the on-chip WDT are rewritten.
• When software standby mode is incorrectly entered.
• When the break mode is incorrectly entered.
In addition, as stated in the NMI above, if an abnormal level is input into the power supply pins or
the system control pins, correct operations cannot be guaranteed.
Except the above cases, the on-chip WDT functions as a device that supports recovery from a
system crash. Accordingly, when a fail-safe function is required in your system, an additional
circuit may be required as necessary.
Rev. 7.00 Sep 21, 2005 page 449 of 878
REJ09B0259-0700