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(5) Do not apply 12 V to the V
caused by accidental programming or erasing, apply 12 V to V
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programmed or erased, or when flash memory is emulated by RAM. While 12 V is applied, the
watchdog timer should be running and enabled to halt runaway program execution, so that
program runaway will not lead to overprogramming or overerasing.
(6) Disable watchdog-timer reset output (RESO) while the programming voltage (V
on. If 12 V is applied during watchdog timer reset output (while the RESO pin is low), overcurrent
flow will permanently destroy the reset output circuit. The watchdog timers reset output enable bit
(RSTOE) should not be set to 1.
If a pull-up resistor is externally attached to the V
reverse current from flowing to V
(7) If the watchdog timer generates a reset output signal when 12 V is not applied, the rise and
fall of the reset output waveform will be delayed by any decoupling capacitors connected to the
V
pin.
PP
+5 V
+12 V
1.0 µF
Figure 18-31 V
pin during normal operation. To prevent microcontroller errors
PP
/RESO pin, a diode is necessary to prevent
PP
when V
is applied (figure 18-31).
CC
PP
Pull-up resistor and
a diode
0.01 µF
Power Supply Circuit Design (Example)
PP
628
only when the flash memory is
PP
V
/
PP
RESO
H8/3048F
) is turned
PP
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