R01UH0823EJ0100 Rev.1.00
Page 246 of 1823
Jul 31, 2019
RX23W Group
11. Low Power Consumption
11.6.3.2
Exit from Software Standby Mode
Exit from software standby mode is initiated by an external pin interrupt (the NMI, IRQ0, IRQ1, IRQ4 to IRQ7),
peripheral function interrupts (the RTC alarm, RTC interval, IWDT, voltage monitoring, VBATT pin voltage drop
detection, USB, and ELC (LPT-dedicated interrupt)), a RES# pin reset, a power-on reset, a voltage monitoring reset, or
an independent watchdog timer reset. When any trigger which initiates exit from software standby mode is asserted, the
oscillators which were operating before entry to software standby mode restart operation. After the oscillation of all these
oscillators has been stabilized, operation returns from software standby mode.
Initiated by an interrupt
When an interrupt request from among the NMI, IRQ0, IRQ1, IRQ4 to IRQ7, RTC alarm, RTC interval, IWDT,
voltage monitoring, VBATT pin voltage drop detection, USB, and ELC (LPT-dedicated interrupt) interrupts is
generated, each of the oscillators which was operating before the transition to software standby mode resumes
oscillation. After the oscillation stabilization wait time of each oscillator set by the MOSCWTCR.MSTS[4:0] bits
has elapsed, the MCU exits software standby mode and interrupt exception processing starts.
Initiated by a RES# pin reset
Clock oscillation starts when the low level is applied to the RES# pin. Clock supply for the MCU starts at the same
time. Keep the level on the RES# pin low over the time required for oscillation of the clocks to become stable. Reset
exception processing starts when the high level is applied to the RES# pin.
Initiated by a power-on reset
A power-on reset asserts a reset to the MCU.
When a power-on reset is negated by a rise in the supply voltage, the CPU starts the reset exception handling.
Initiated by a voltage monitoring reset
A voltage monitoring reset asserts a reset to the MCU.
When a voltage monitoring reset is negated by a rise in the supply voltage, the CPU starts the reset exception
handling.
Initiated by an independent watchdog timer reset
An internal reset generated by an IWDT underflow asserts a reset to the MCU.
Note that the independent watchdog timer is stopped in software standby mode due to the register settings
(OFS0.IWDTSTRT = 0 and OFS0.IWDTSLCSTP = 1, or OFS0.IWDTSTRT = 1 and IWDTCSTPR.SLCSTP = 1)
in software standby mode. In that case, exit from software standby mode by the independent watchdog timer reset
cannot be done.