ASC7621 データシートの表示（PDF） - Unspecified

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ASC7621

HARDWARE MONITOR WITH INTEGRATED FAN CONTROL

Unspecified 

aSC7621

PECI

The aSC7621 is compatible with devices that are

compliant with Intel’s PECI 1.0 specifications. More

information on this interface may be found in their PECI

interface specifications.

Temperatures sent over the PECI interface from the CPU

are in Celsius degrees relative to the Thermal Control

Circuit (TCC) temperature stored internally in the CPU

and accessed only through BIOS. This is the temperature

limit where internal measures are taken to reduce power

dissipation. Fan speed control settings sent by the BIOS

over the SMBus to registers in the aSC7621 are made

using this relative temperature rather than the absolute

readings of remote or on-chip diodes.

As many as four CPU clients on the PECI bus are

addressed in the range of 0x30 to 0x33. Currently, each

address is a single-packaged device that may have up to

two domains or CPU-measured digital temperatures.

General Operation

The PECI host in aSC7621 performs the following

functions:

• Responds to SMBus configuration identifying the

presence of PECI clients and the Thermal Zone

associated with each client.

• Reads the PECI temperature of the domain(s) of

each client processor addressed.

• Stores the highest result from each PECI

address into Temperature Zone register

associated to the measurement received from

the client. (each address may be associated with

any one Temperature Zone.)

• Flags an error if no valid PECI temperature can

be read.

• Continuously monitors the state of the PECI

interface for fault conditions.

PECI temperatures assigned to a Temperature Zone are

reported over SMBus interface in Temperature Zone

registers also will be in the range 0°C to -127°C. The

format reported through Temperature Zone registers is

re-aligned to agree with diode measurements. It is stored

in two register locations in the following format with

integer high byte and fractional low byte to be consistent

with all other temperature reports:

Temperature

0° C

-1° C

-5° C

-32° C

-127° C

2’s Complement

Representation

High Byte

Low Byte

0000 0000 .0000 0000

1111 1111 .0000 0000

1111 1011 .0000 0000

1110 0000 .0000 0000

1000 0001 .0000 0000

Table 2 PECI Temperature Report Format

PECI Errors

A specific set of temperature reading value encodings,

well outside the operational range of 0°C to -127°C, are

reserved to signal temperature sensor faults on the CPU

to aSC7621 interface. These encodings are in the PECI

temperature format as delivered by the CPU and are

converted to the appropriate Interrupt Status Register 3

error bits described in the Interrupt Status register section

below.

PECI Temperature Format and Range

The PECI temperatures read from the processor will be in

the range 0°C to -127°C where 0°C is the hottest

temperature and has the following format:

Temperature

0° C

-1° C

-5° C

-32° C

-127° C

2’s Complement

Representation

0000 0000 00.00 0000

1111 1111 11.00 0000

1111 1110 11.00 0000

1111 1000 00.00 0000

1111 0000 01.00 0000

Table 1 Raw PECI Temperature Format

These readings are not accessible to the user but are

filtered, re-formatted and assigned to a Temperature

Zone. Filtered PECI Temperature readings are accessible

by the user before they are assigned to a Temperature

Zone by reading registers F6h through FDh. These

readings follow the format described in Table 2. The

© Andigilog, Inc. 2006

- 11 -

www.andigilog.com

October 2006 - 70A06010

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