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CHAPTER 3 CPU
3.8
Standby Mode (Low Power Consumption)
The sleep mode, stop mode, and watch mode are available as the standby mode. A
transition to the standby mode is caused by settings of the standby control register
(STBC) both in main clock mode and subclock mode.
In main clock mode, transitions to the sleep mode and stop mode are possible. In
subclock mode, transitions to the sleep mode, stop mode, and watch mode are
possible. Power consumption can be reduced by stopping operations of CPU and
peripheral functions using the standby mode. This section describes the relations
between the standby mode and clock mode, and the operating states of each section
in standby mode.
I
Standby Mode
In clock mode, power consumption is reduced by reducing the operating clock of CPU and
peripheral circuits such as switching of the main clock and subclock or switching of the main
clock speed (gear function). In standby mode, however, power consumption is reduced by the
clock supply stop (sleep mode) to CPU by the clock controller, clock supply stop (watch mode)
to CPU and peripheral circuits, or stop of the oscillation itself (stop mode).
H
Main sleep mode
The main sleep mode is a mode which stops operations of CPU and the watchdog timer.
Peripheral functions excluding the watch prescaler operate on the main clock (Part of the
functions can operate on the subclock).
H
Sub-sleep mode
The sub-sleep mode is a mode which stops the main clock oscillation, CPU operations, and
watchdog timer and timebase timer operations. Peripheral functions operate on the subclock.
H
Main stop mode
The main stop mode is a mode which stops operations of CPU and peripheral functions. The
main clock stops oscillation, but the subclock continues oscillation. In this mode, all functions
are stopped excluding external interrupts, count operations of the watch prescaler, and some of
the functions that run with the subclock.
H
Sub-stop mode
The sub-stop mode is a mode which stops all functions other than external interrupts. The main
clock and the subclock both stop oscillation.
H
Watch mode
The clock mode is a mode a transition to which is possible only from the subclock mode. All
functions other than the watch prescaler (watch interrupt), external interrupts, and part of the
functions operating on the subclock stop.