UM0851 datasheet(220/245 Pages) STMICROELECTRONICS

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Power management section

UM0851

220/245

Doc ID 16604 Rev 2

Power management section

"Power Management" means that parts of your computer are shut off or put into a power

conserving mode if they are not being used. The techniques of clock frequency are also part

of power management.

10.1

Hardware overview

The hardware section has been divided into two subsections based on the power

management techniques that have been used in the software. Each subsection is based on

the software architectures that have been followed in the design.

10.1.1

Power management techniques

The System Control State Machine allows you to reduce power consumption by controlling

the clock inputs to the CPU. It has four states:

●

SLEEP

●

DOZE (reset state)

●

SLOW

●

NORMAL

All transitions between states are software controllable except for SLEEP to DOZE which is

activated only by a hardware event.

Figure 64.

System control state machine

The system control state machine is used to select the input frequency applied to the

system.

DOZE

SLOW

SLEEP

NORMAL

Performances

Consumption

IRQ, FIQ

and RESET

Dynamic

Frequency

Scaling

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