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Rev. 5.00, 09/03, page 189 of 760
8.4.2 Canceling Standby Mode
Standby mode is canceled by an interrupt (NMI, IRQ, IRL, PINT, or on-chip peripheral module)
or a reset.
Canceling with an Interrupt: The on-chip WDT can be used for hot starts. When the chip detects
an NMI, IRL, IRQ, PINT
*
1
, or on-chip peripheral module (except interval timer)
*
2
interrupt, the
clock will be supplied to the entire chip and standby mode canceled after the time set in the
WDT’s timer control/status register has elapsed. The STATUS1 and STATUS0 pins both go low.
Interrupt handling then begins and a code indicating the interrupt source is set in the INTEVT and
INTEVT2 registers. After the branch to the interrupt handling routine, clear the STBY bit in the
STBCR register. WTCNT stops automatically. If the STBY bit is not cleared, WTCNT continues
operation and a transition is made to standby mode
*
3
when it reaches H'80. This function prevents
the data from being destroyed due to a rise in voltage with an unstable power supply, etc.
Interrupts are accepted in standby mode even when the BL bit in the SR register is 1. If necessary,
save SPC and SSR to the stack before executing the SLEEP instruction. Immediately after an
interrupt is detected, the phase of the CKIO pin clock output may be unstable, until the processor
starts interrupt handling. (The canceling condition is that the IRL3–IRL0 level is higher than the
mask level in the I3–I0 bits in the SR register.)
Notes: 1. When the RTC is being used, standby mode can be canceled using IRL3–IRL0, IRQ4–
IRQ0, or PINT0/1.
2. Standby mode can be canceled with an RTC or TMU (only when running on the RTC
clock) interrupt.
3. This standby mode can be canceled only by a power-on reset.
WTCNT value
H'FF
H'80
Time
Interrupt
request
WDT overflow and branch to
interrupt handling routine
Crystal oscillator settling
time and PLL synchronization
time
Clear bit STBCR.STBY before
WTCNT reaches H'80. When
STBCR.STBY is cleared, WTCNT
halts automatically.
Figure 8.1 Canceling Standby Mode with STBCR.STBY