ST7FLITE29 STMICROELECTRONICS [STMicroelectronics], ST7FLITE29 Datasheet - Page 38

• Manufacturer Part Number: ST7FLITE29
• Description: 8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY, DATA EEPROM, ADC, TIMERS, SPI
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST7LITE2
9 POWER SAVING MODES
9.1 INTRODUCTION
To give a large measure of flexibility to the applica-
tion in terms of power consumption, five main pow-
er saving modes are implemented in the ST7 (see
Figure
After a RESET the normal operating mode is se-
lected by default (RUN mode). This mode drives
the device (CPU and embedded peripherals) by
means of a master clock which is based on the
main oscillator frequency divided or multiplied by 2
(f
From RUN mode, the different power saving
modes may be selected by setting the relevant
register bits or by calling the specific ST7 software
instruction whose action depends on the oscillator
status.
Figure 21. Power Saving Mode Transitions
38/131
1
OSC2
AUTO WAKE UP FROM HALT
Slow
Wait (and Slow-Wait)
Active Halt
Auto Wake up From Halt (AWUFH)
Halt
).
21):
ACTIVE HALT
SLOW WAIT
POWER CONSUMPTION
SLOW
WAIT
HALT
RUN
Low
High
9.2 SLOW MODE
This mode has two targets:
– To reduce power consumption by decreasing the
– To adapt the internal clock frequency (f
SLOW mode is controlled by the SMS bit in the
MCCSR register which enables or disables Slow
mode.
In this mode, the oscillator frequency is divided by
32. The CPU and peripherals are clocked at this
lower frequency.
Note: SLOW-WAIT mode is activated when enter-
ing WAIT mode while the device is already in
SLOW mode.
Figure 22. SLOW Mode Clock Transition
internal clock in the device,
the available supply voltage.
SMS
f
CPU
f
OSC
f
OSC
NORMAL RUN MODE
/32
REQUEST
f
OSC
CPU
) to