Temperature Sensor and System Monitor
in a 10-Pin 礛AX
______________________________________________________________________________________ 11
SMBCLK
A
B
C
D
E F
G
H
I J K
SMBDATA
t
SU:STA
t
HD:STA
t
LOW
t
HIGH
t
SU:DAT
t
HD:DAT
t
SU:STO
t
BUF
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
L
M
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
I = MASTER PULLS DATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
Figure 3. I
2
C/SMBus Write Timing Diagram
Write Byte Format
Read Byte Format
Send Byte Format
Receive Byte Format
Slave Address: equiva-
lent to chip-select line of
a 3-wire interface
Command Byte: selects which
register you are writing to
Data Byte: data goes into the register
set by the command byte (to set
thresholds, configuration masks, and
sampling rate)
Slave Address: equiva-
lent to chip-select line
Command Byte: selects
which register you are
reading from
Slave Address: repeated
due to change in data-
flow direction
Data Byte: reads from
the register set by the
command byte
Data Byte: writes data to the
register commanded by the
last read byte or write byte
transmission
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
S = Start condition
P = Stop condition
Shaded = Slave transmission
A = Not acknowledged
ACK
7 bits
ADDRESS
ACK
8 bits
DATA
ACK
P
8 bits
S
COMMAND
WR
ACK
7 bits
ADDRESS
ACK
S
ACK
8 bits
DATA
7 bits
ADDRESS
RD
8 bits
P
S
COMMAND
A
WR
ACK
7 bits
ADDRESS
8 bits
COMMAND
ACK P
S
WR
ACK
7 bits
ADDRESS RD
8 bits
DATA
P
S
A
Figure 2. I
2
C/SMBus Protocols