UM0851 datasheet(222/245 Pages) STMICROELECTRONICS

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Power management section

UM0851

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Doc ID 16604 Rev 2

modules driven by the CLK_PLL1 signal, DCS can completely switch OFF the clock of

an unused module and quickly switch it ON again when it is required.

With this technique the processor, or system, can run at maximum frequency and

achieve its maximum performance.

For complete flexibility DCS is fully software controllable via the PERIP1_CLK_ENB

application is waiting for an event. The system can switch OFF the clock to modules

that are not used and enable them, with a low latency, when needed.

Modules that support this feature are shown in the tables below.

●

Combining frequency scaling and clock switching techniques (DFS+DCS)

In NORMAL state, the best active power saving results are obtained by combining both

the previously described power-management techniques .

These techniques can be used to reduce the power consumption of the devices while still

allowing fast response to critical tasks, that can be always be performed at maximum

frequency, if needed.

10.2

Software overview

The section describes the various Power Management systems already present in the Linux

kernel that used in SPEAr applications to manage power in an efficient way.

Table 61.

SPEAr600 modules with DCS feature

Module

USB 2.0 host 1

GPIO 3

GPIO 4

I2C

USB 2.0 host 2(For

Spear600)

UART-1

UART-2

TIMER-1

TIMER-2

TIMER-3

TIMER-4

TIMER-5

CLCD CTRL

IRDA

ARM-1 SUBSYSTEM

ARM-2 SUBSYTEM

USB2.0 Device

Flash Serial(SMI)

Flash NAND(FSMC)

PLL-1

Internal ROM

JPEG Codec

PLL-2

PLL-3

DMA

ADC

SPI-1

SPI-2

RTC

SPI-3

ARM-1

Ethernet

Table 62.

SPEAr300 modules with DCS feature