CHAPTER 6: Low Power Consumption Mode
FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E 191
Overview of Run Modes
A Run mode is defined according to which clock is selected as the master clock. A base clock acquired by
dividing a master clock frequency is supplied to the CPU clock, the AHB bus clock and the APB bus clock
to run the CPU, buses and most peripherals.
The source clock frequency can be modified dynamically. The source clock oscillator can be stopped
when the main oscillator or the sub oscillator is not used.
Below are the five Run modes, which are defined according to the clock selected as the master clock.
High speed CR run mode
In this mode, the high speed CR oscillator clock is used as the master clock. The main oscillator or the
sub oscillator can be stopped when not used. The state of the PLL Multiplier Circuit changes according to
the setting of the PLLE bit. The low speed CR oscillator is always in the active state. The system transits
to this mode after a reset has been released.
Main run mode
In this mode, the main oscillator clock is used as the master clock. The respective states of the PLL
Multiplier Circuit and the sub oscillator change according to the respective settings of the PLLE bit and
the SOSCE bit, respectively. The high speed CR oscillator and the low speed CR oscillator are always in
the active state.
PLL run mode
In this mode, the PLL clock acquired by multiplying a PLL multiplier to the main oscillator clock or the high
speed CR oscillator clock is used as the master clock. The high speed CR oscillator and the low speed
CR oscillator are always in the active state. The respective states of the main oscillator and the sub
oscillator change according to the respective settings of the MOSCE bit and the SOSCE bit, respectively.
Low speed CR run mode
In this mode, the low speed CR oscillator clock is used as the master clock. The state of the sub oscillator
changes according to the setting of the SOSCE bit. The main oscillator, the high speed CR oscillator and
the PLL Multiplier Circuit cannot be used.
Sub run mode
In this mode, the sub oscillator clock is used as the master clock. The low speed CR oscillator is always in
the active state. The main oscillator, the high speed CR oscillator and the PLL Multiplier Circuit cannot be
used.
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