±1°C, SMBus-Compatible Remote/Local

Temperature Sensor with Overtemperature Alarm

6

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S

ADDRESS

WR

ACK

ACK

P

DATA

ACK

COMMAND

7 BITS

1

8 BITS

8 BITS

SLAVE ADDRESS: EQUIVA-

LENT TO CHIP-SELECT LINE OF

A 3-WIRE INTERFACE

DATA BYTE: DATA GOES INTO THE REGISTER

SET BY THE COMMAND BYTE (TO SET

THRESHOLDS, CONFIGURATION MASKS, AND

SAMPLING RATE)

WRITE BYTE FORMAT

S

ADDRESS

ADDRESS

WR

ACK

ACK

P

S

RD

ACK

///

DATA

COMMAND

7 BITS

7 BITS

8 BITS

8 BITS

READ BYTE FORMAT

SLAVE ADDRESS: EQUIVA-

LENT TO CHIP SELECT LINE

COMMAND BYTE: SELECTS

WHICH REGISTER YOU ARE

REDING FROM

SP

ADDRESS

WR

ACK

ACK

COMMAND

7 BITS

8 BITS

SEND BYTE FORMAT

COMMAND BYTE: SENDS COM-

MAND WITH NO DATA, USUALLY

USED FOR ONE-SHOT COMMAND

SP

ADDRESS

RD

ACK

///

DATA

7 BITS

8 BITS

RECEIVE BYTE FORMAT

DATA BYTE: READS DATA FROM

THE REGISTER COMMANDED

BY THE LAST READ BYTE OR

WRITE BYTE TRANSMISSION;

ALSO USED FOR SMBUS ALERT

RESPONSE RETURN ADDRESS

SLAVE ADDRESS: REPEATED

DUE TO CHANGE IN DATA-

FLOW DIRECTION

DATA BYTE: READS FROM

THE REGISTER SET BY THE

COMMAND BYTE

S = START CONDITION

P = STOP CONDITION

SHADED = SLAVE TRANSMISSION

/// = NOT ACKNOWLEDGED

Figure 1. SMBus Protocols

SMBCLK

A = START CONDITION

B = MSB OF ADDRESS CLOCKED INTO SLAVE

C = LSB OF ADDRESS CLOCKED INTO SLAVE

D = R/W BIT CLOCKED INTO SLAVE

AB

C

D

E

FG

HI

J

SMBDATA

LM

K

E = SLAVE PULLS SMBDATA LINE LOW

F = ACKNOWLEDGE BIT CLOCKED INTO MASTER

G = MSB OF DATA CLOCKED INTO SLAVE

H = LSB OF DATA CLOCKED INTO SLAVE

I = SLAVE PULLS DATA LINE LOW

J = ACKNOWLEDGE CLOCKED INTO MASTER

K = ACKNOWLEDGE CLOCK PULSE

L = STOP CONDITION

M = NEW START CONDITION

Figure 2. SMBus Write Timing Diagram