CHAPTER 20 RESET FUNCTION
User’s Manual U16896EJ2V0UD
595
20.4.2 Reset operation by WDTRES1 signal
If a reset operation mode in which reset is effected when watchdog timer 1 overflows is set, the system is reset
when watchdog timer 1 overflows (when the WDTRES1 signal is generated), and each hardware unit is initialized to a
specific status.
After watchdog timer 1 has overflowed, the system is reset for a specific duration of time (f
CLK
: 12 clocks) and then
automatically released from the reset status. After release of the reset status, the CPU starts program execution.
Note that, because the main clock oscillator continues operating even during the reset period, the oscillation
stabilization time is not secured.
The following table shows the status of each hardware unit during the period of reset that is effected by the
WDTRES1 signal and after release of the reset status.
Table 20-3. Hardware Status on Occurrence of WDTRES1 Signal
Item
During Reset
After Reset
Main clock oscillator (f
X
) Oscillation
continues
Subclock oscillator (f
XT
) Oscillation
continues
Internal oscillator (f
R
) Oscillation
continues
Peripheral clock (f
XX
to f
XX
/1024)
Operation stops
Operation starts
Internal system clock (f
CLK
)
Oscillation continues (initialized to f
XX
/8)
CPU clock (f
CPU
)
Oscillation continues (initialized to f
XX
/8)
Watchdog timer 1 clock (f
XW
) Operation
continues
Internal RAM
Undefined if writing data to RAM (by CPU) and reset input conflict (data is damaged).
Otherwise value immediately before reset input is retained.
I/O lines (P00)
Low-level output
I/O lines (ports other than P00)
High impedance
On-chip peripheral I/O registers
Initialized to specified status
Watchdog timer 2
Operation stops Operation
starts
(f
R
/8)
Other on-chip peripheral functions Operation
stops
Operation can be started
Figure 20-5. Timing of Reset Operation by Watchdog Timer 1
Initialized to f
XX
/8 operation
f
CLK
: 12-clock width
Internal system
reset signal
(active low)
WDTRES1 signal
(active low)
f
X
f
CLK
Содержание ?PD703302
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