MAX6621AUB+ Datasheet MAX6621AUB+, MAX6621AUB+T | P10-P12

MAX6621

PECI-to-I

C Translator

10 ______________________________________________________________________________________

Temperature Commands

Table 11 shows the different commands for selecting

one of the PECI hosts or getting the maximum tempera-

ture. Read commands are initiated by the MAX6621,

and the result returned is a 16-bit word with the least

significant bit (LSB) clocked in first for the selected

PECI host.

The result consists of RESLO for the 8 LSBs and RESHI

for the 8 MSBs, resulting in a 16-bit word. The 16-bit

words are temperature values read from the PECI inter-

face. PECI-enabled Intel microprocessors return tem-

perature data in fractions of 1°C below the

thermal-control-circuit activation point, resulting in neg-

ative return values that do not represent absolute tem-

peratures. Absolute temperatures can be achieved by

setting the temperature offset in CONFIG2.

Table 12 shows example return values for an Intel CPU.

Note that the MAX6621 does not interpret the return

ADDRESS REGISTER TYPE RESULT

00h Socket 0, domain 0

01h Socket 0, domain 1

02h Socket 1, domain 0

03h Socket 1, domain 1

04h Socket 2, domain 0

05h Socket 2, domain 1

06h Socket 3, domain 0

07h Socket 3, domain 1

08h

Read maximum temperature for all enabled

sockets/domains

ReadWord 16-bit words

Table 11. Read Temperature

CONFIG2 RESHI:RESLO

RELATIVE

TEMPERATURE (°C)

16 BITS ALTERNATE 16 BITS ALTERNATE

0000 0000 FFC0 FFFF

-1

17C0 005F 1780 005E

0000 0000 F700 FFDC

-36

17C0 005F 0ec0 003B

0000 0000 F6C0 FFDB

-37

17C0 005F 0E80 003A

0000 0000 F680 FFDA

-38

17C0 005F 0E40 0039

0000 0000 F640 FFD9

-39

17C0 005F 0E00 0038

0000 0000 F600 FFD8

-40

17C0 005F 0DC0 0037

0000 0000 F5C0 FFD7

-41

17C0 005F 0D80 0036

0000 0000 F580 FFD6

-42

17C0 005F 0D40 0035

0000 0000 F540 FFD5

-43

17C0 005F 0D00 0034

Table 12. Return Temperature Values

MAX6621

PECI-to-I

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______________________________________________________________________________________ 11

data (with the exception of error codes) and the relative

temperatures are listed for reference only. Table 12

shows the values with 16-bit and alternate word format.

The read maximum temperature command from Table 11

returns the highest temperature that is not an error

code from the enabled PECI sockets and domains. This

operation works on signed numbers only and does not

give information as to what socket the temperature

result comes from. To find the socket and domain, use

the read maximum temperature address command as

shown in Table 13.

The read maximum temperature address command

returns the register that had the highest temperature

when read maximum temperature was last called. An

error is returned if the read maximum temperature has

not been called or when the read maximum tempera-

ture itself returns an error.

Return Value Flow Chart

Figure 4 shows the operations performed on tempera-

ture data read through PECI.

COMMAND DESCRIPTION TYPE RESULT

0Ah

Read address of

socket/domain with the

maximum temperature

ReadWord 16-bit

Table 13. Read Maximum Temperature

Address

ERROR?

DATA FROM PECI

RETURN DATA ON I

ADD OFFSET

ALT.

FORMAT?

AVERAGING

CONVERT

DATA

FORMAT

Figure 4. Operational Flowchart

MAX6621

Error Codes

Error codes are represented as 16-bit words in the

8000h–81FFh range as shown in Table 14.

ALERT

Output

The MAX6621 asserts ALERT when a PECI temperature

exceeds a configurable threshold after averaging.

Table 15 below shows the registers that set the thresh-

old and read the alert temperature for each socket. If

there are no active alerts, an error is returned as shown

in Table 14. If polling is disabled, the alert temperatures

are only checked when the request polling command is

called.

Once ALERT is asserted, a subsequent drop in temper-

ature does not clear the alert. ALERT must be cleared

by calling the clear alert command.

Clear Alert

The clear alert is shown in Table 16, and this command

clears an active alert. If the temperature still exceeds

one of the thresholds after clearing, ALERT reasserts

on the next PECI temperature read. New alerts are dis-

abled when mask alerts (CONFIG0, bit 4) is set. This

does not affect an existing alert. The clear alert com-

mand needs to be called to clear it.

Read Alert Socket/Domain

Table 17 shows the read alert socket/domain com-

mand. Call this command to check for the socket/

domain (register) that caused the alert to become

active. If multiple temperatures exceed their respective

thresholds, only the first violation is recorded. Register

address is held in low byte.

PECI-to-I

C Translator

12 ______________________________________________________________________________________

ERROR

CODES

DESCRIPTION

8000h–

80FFh

Refer to Intel PECI specification.

8100h

PECI transaction failed for more than the

configured number of consecutive retries.

8101h Polling disabled for requested socket/domain.

8102h

First poll not yet completed for requested

socket/domain (on startup).

8103h

Read maximum temperature requested, but no

sockets/domains enabled or all enabled

sockets/domains have errors; or read maximum

temperature address requested, but read

maximum temperature was not called.

8104h

Get alert socket/domain requested, but no alert

active.

Table 14. Error Codes

COMMAND DESCRIPTION TYPE DEFAULT

10h

Read/write alert

temperature for

socket 0

ReadWord/

WriteWord

7FFFh

11h

Read/write alert

temperature for

socket 1

ReadWord/

WriteWord

7FFFh

12h

Read/write alert

temperature for

socket 2

ReadWord/

WriteWord

7FFFh

13h

Read/write alert

temperature for

socket 3

ReadWord/

WriteWord

7FFFh

Table 15. Read/Write Temperature Alert

Commands

COMMAND DESCRIPTION TYPE

15h Clear alert SendByte

Table 16. Clear Alert

COMMAND DESCRIPTION TYPE RESULT

0Bh

Read alert socket

and domain

ReadWord 16-bit word

Table 17. Read Alert Socket/Domain

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