ST7DALIF2 datasheet(50/171 Pages) STMICROELECTRONICS

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Power saving modes

ST7DALIF2

50/171

Power saving modes

11.1

Introduction

To give a large measure of flexibility to the application in terms of power consumption, five

main power saving modes are implemented in the ST7 (see Figure 20):

■ Slow

■ Wait (and Slow-Wait)

■ Active-halt

■ Auto Wake up From Halt (AWUFH)

■ Halt

After a RESET the normal operating mode is selected 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 (fOSC2).

From RUN mode, the different power saving modes may be selected by setting the relevant

oscillator status.

Figure 20.

Power saving mode transitions

11.2

Slow mode

This mode has two targets:

●

To reduce power consumption by decreasing the internal clock in the device,

●

To adapt the internal clock frequency (fCPU) to the available supply voltage.

Slow mode is controlled by the SMS bit in the MCCSR register which enables or disables

Slow mode.

POWER CONSUMPTION

Wait

Slow

RUN

Active-halt

High

Low

Slow Wait

AUTO WAKE UP FROM Halt

Halt

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