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Clock Generator
Chapter 4
Preliminary User’s Manual U17566EE1V2UM00
4.1.3
Power save modes overview
The microcontroller provides the following stand-by modes: HALT, IDLE,
WATCH, Sub-WATCH, and STOP. Application systems which are designed in a
way that they switch between these modes according to operation purposes,
reduce power consumption efficiently.
The following explanations provide a general overview and refer to the default
settings. Some settings can be changed, for example the activity of the watch
and watchdog clocks and hence the connected timers.
For details, please refer to
“Power save modes description” on page 167
and
the register descriptions.
HALT mode
In this mode, the
clock supply to the CPU
is suspended while other on-chip
peripherals continue to operate. Combining this mode with the normal
operating mode results in intermittent operation and reduces the overall
system power consumption.
This mode is entered by executing the HALT instruction.
All other power save modes are entered by setting the registers PSM and PSC.
IDLE mode
In this mode, the
clock distribution
is stopped and hence the whole system.
The oscillators, Clock Generator (PLL, SSCG, frequency multipliers, dividers),
Watch Timer, and Watchdog Timer remain operating.
This mode allows quick return to the normal operating mode in response to a
release signal, because it is not necessary to wait for oscillators or PLLs to
settle.
This mode provides low power consumption. Power is only consumed by the
oscillators (main oscillator, sub oscillator), Clock Generator (PLL and SSCG),
and Watch Timer / Watchdog Timer.
WATCH mode
In this mode, the
Clock Generator
(PLL and SSCG) stops operation.
Therefore, the entire system except Watch Timer / Watchdog Timer stops.
This mode provides low power consumption. Power is only consumed by the
oscillators (main oscillator, sub oscillator), and the Watch Timer / Watchdog
Timer circuits.
Sub-WATCH mode
In this mode, not only the Clock Generator is stopped but also the
main
oscillator
. Watch Timer / Watchdog Timer are switched to the sub or ring
oscillator. Therefore, the entire system except Watch Timer / Watchdog Timer
stops.
This mode provides very low power consumption. Power is only consumed by
the sub oscillator and Watch Timer / Watchdog Timer circuits.
STOP mode
In this mode, the entire system stops.
This mode provides ultra-low power consumption. Power is only consumed by
leakage current and the sub oscillator (if a crystal is connected).
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