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6.4 Power Save Functions
6.4.1 Outline
This product provides the following power saving functions.
These modes can be combined and switched to suit the target application, which enables effective implementation
of low-power systems.
(1) HALT mode
When in this mode, the clock's oscillator continues to operate but the CPU's operating clock is stopped. A clock
continues to be supplied for other on-chip peripheral functions to maintain operation of those functions. This
enables the system's total power consumption to be reduced.
A dedicated instruction (the HALT instruction) is used to switch to HALT mode.
(2) IDLE mode
This mode stops the entire system by stopping the CPU's operating clock as well as the operating clock for on-
chip peripheral functions while the clock oscillator is still operating. However, the subclock continues to operate
and supplies a clock to the on-chip peripheral functions.
When this mode is released, there is no need for the oscillator to wait for the oscillation stabilization time, so
normal operation can be resumed quickly.
When the IDLE bit of the power saving control register (PSC) is set to 1, the system switches to IDLE mode.
(3) Software STOP mode
This mode stops the entire system by stopping the main clock oscillator. The subclock continues to be supplied
to keep on-chip peripheral functions operating. If a subclock is not used, ultra low power consumption mode
(leak current only) is set. STOP mode setting is prohibited if the CPU is operating via the subclock.
If the STP bit of the PSC register is set to 1, the system enters STOP mode.
(4) Subclock operation
In this mode, the CPU clock is set to operate using the subclock and the MCK bit of the PCC register is set to 1
to set low power consumption mode in which the entire system operates using only the subclock.
When IDLE mode is set, the CPU's operating clock and some peripheral functions (DMAC and BCU) are
stopped, so that power consumption can be reduced even more than in HALT mode.
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CHAPTER 6
CLOCK GENERATION FUNCTION
User's Manual U13850EJ6V0UD
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