CHAPTER 6: Low Power Consumption Mode
FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E 193
Overview of Timer Modes
Timer mode is classified as a standby mode. In Timer mode, the base clock supply stops. Since the stop
of the base clock supply causes the CPU clock, the AHB bus clock and all APB bus clocks to stop, power
consumption is further reduced. In Timer mode, all functions stop operating except for the following: all
oscillators, PLL, hardware watchdog timer, watch counter, RTC, clock failure detector and Low Voltage
Detection Circuit.
Below are the five Timer modes, which are defined according to the master clock used at the transition to
TIMER mode.
High speed CR timer mode
With the high speed CR oscillator clock selected as the master clock, the system transits to high speed
CR timer mode when a request for transition to Timer mode is made. The respective states of the PLL
Multiplier Circuit, the main oscillator and the sub oscillator change according to the respective settings of
the PLLE bit, the MOSCE bit and the SOSCE bit, respectively. The low speed CR oscillator is always in
the active state.
Main timer mode
With the main clock selected as the master clock, the system transits to main timer mode when a request
for transition to Timer mode is made. 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 timer mode
With the PLL clock selected as the master clock, the system transits to PLL timer mode when a request
for transition to Timer mode is made. 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 timer mode
With the low speed CR oscillator clock selected as the master clock, the system transits to low speed CR
timer mode when a request for transition to Timer mode is made. 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 timer mode
With the sub-clock selected as the master clock, the system transits to sub timer mode when a request for
transition to Timer mode is made. The low speed CR oscillator are always in the active state. The main
oscillator, the high speed CR oscillator and the PLL Multiplier Circuit cannot be used.
Overview of RTC Mode
RTC mode is classified as a standby mode. In RTC mode, all oscillators stop except for the sub oscillator.
All functions stop operating except for the watch counter, the RTC and the Low Voltage Detection Circuit.
Overview of Stop Mode
Stop mode is classified as a standby mode. In Stop mode, all oscillators stop. All functions stop operating
except for the Low Voltage Detection Circuit.
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