CS5535 datasheet(159/555 Pages) NSC

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4.17 POWER MANAGEMENT CONTROL

The Power Management Control (PMC) module is a

GeodeLink Device whose function is to control all aspects

of power management. Power management is event driven

meaning that, in general, any action that the PMC performs

is predicated on some event. These events can come from

other GeodeLink Devices, including the CPU module inside

the GX2 for example, or events coming from other off-chip

sources.

The PMC is compatible with the industry standard power

management capabilities as defined in the Advanced Con-

figuration and Power Interface (ACPI) v2.0 specification. An

OS that conforms to ACPI can take advantage of the

CS5535 ACPI support hardware.

Advanced Power Management (APM) is another power

management approach that the PMC supports. APM is a

subset of ACPI and therefore will not be directly discussed.

Components in a GeodeLink architecture based system

have hardware and software means of performing power

management which the PMC controls. A high performance

computing system consumes multiple watts of power when

fully on. However, with GeodeLink architecture, system

power consumption is significantly lower on average

through the use of power states that reduce power needs

when the system is idle.

4.17.1 Power Domains

The PMC module consists of three blocks: Working

Standby and RTC.

• The Working block contains all circuits and functions

associated with the Working power domain. It includes

the Working state machine, Local bus interface, ACPI

power management registers, and power management

supporting logic (i.e., counters, timer, CCU, etc.). The

main function of the Working block is to put the system

into Sleep, that is, turn off clocks to the system and

disable I/Os to reduce power consumption.

• The Standby block contains all circuits and functions

associated with the Standby power domain. It includes

the Standby state machine, ACPI registers, and power

management supporting logic (i.e., counters, reset,

CCU, etc.). The function of the Standby logic is to

control power to the Working power domain. The PMC

disables all interfaces between the Standby and Working

domains while the Working power is off.

• The RTC block contains the timing circuits for keeping

real time. These circuits are powered by VBAT (ball A3).

It is not a device requirement that the RTC block be

powered during Mechanical Off. If a system design does

not require that real time be kept, then VBAT should be

tied to ground.

4.17.2 Power States

Table 4-34 shows the supported ACPI power states and

how they relate to the CS55335/GX2. ACPI power states

not described are not supported.

Table 4-34. Supported ACPI Power Management States

ACPI States

Hardware States

Global System

State

Sleep State

C State

GX2 State

CS5535

Working

Logic

System

Main

Memory

CS5535

Standby

Logic

G0: Working

AHCG

Suspend on

Halt

AHCG

G1: Idle

S1: Sleeping

Sleep

Auto-refresh

On (Sleep)

S3: Save-to-RAM

Off

Auto-refresh

Standby

S4: Save-to-Disk

Off

G2: Soft Off

Off

Standby

G3: Mechanical Off

Off

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