445
18.4.2
Exit from Software Standby Mode
Software standby mode can be exited by input of an external interrupt at the NMI,
IRQ
0
,
IRQ
1
, or
IRQ
2
pin, or by input at the
RES
or
STBY
pin.
Exit by Interrupt: When an NMI, IRQ
0
, IRQ
1
, or IRQ
2
interrupt request signal is received, the
clock oscillator begins operating. After the oscillator settling time selected by bits STS2 to STS0
in SYSCR, stable clock signals are supplied to the entire chip, software standby mode ends, and
interrupt exception handling begins. Software standby mode is not exited if the interrupt enable
bits of interrupts IRQ
0
, IRQ
1
, and IRQ
2
are cleared to 0, or if these interrupts are masked in the
CPU.
Exit by
RES
Input: When the
RES
input goes low, the clock oscillator starts and clock pulses are
supplied immediately to the entire chip. The
RES
signal must be held low long enough for the
clock oscillator to stabilize. When
RES
goes high, the CPU starts reset exception handling.
Exit by
STBY
Input: Low input at the
STBY
pin causes a transition to hardware standby mode.
18.4.3
Selection of Waiting Time for Exit from Software Standby Mode
Bits STS2 to STS0 in SYSCR and bits DIV1 and DIV0 in DIVCR should be set as follows.
Crystal Resonator: Set STS2 to STS0, DIV1, and DIV0 so that the waiting time (for the clock to
stabilize) is at least 7 ms. Table 18.3 indicates the waiting times that are selected by STS2 to
STS0, DIV1, and DIV0 settings at various system clock frequencies.
When Using an External Clock: Any setting is permitted.
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