MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I
2
C-Compatible Serial Interface
6 _______________________________________________________________________________________
Write Byte Format
S ADDRESS WR
ACK COMMAND ACK DATA ACK P
7 bits 8 bits 8 bits
Slave Address:
equivalent
to chip-select line of a 3-
wire interface
Command Byte: selects
register you are writing to
Data Byte: data goes into the register set by the
command byte
Write Word Format
S ADDRESS WR
ACK COMMAND ACK DATA ACK DATA ACK P
7 bits 8 bits
8 bits
(MSB)
8 bits
(LSB)
Slave Address:
equivalent to chip-select
line of a
3-wire interface
Command Byte:
selects register you
are writing to
Data Bytes: data goes into the
register set by the command
byte
Read Byte Format
S ADDRESS WR
ACK COMMAND ACK S ADDRESS RD ACK DATA /// P
7 bits 8 bits 7 bits 8 bits
Slave Address: equivalent
to chip-select line
Command Byte:
selects 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
Read Word Format
S ADDRESS WR
ACK COMMAND ACK S ADDRESS RD ACK DATA ACK DATA /// P
7 bits 8 bits 7 bits 8 bits
(MSB)
8 bits
(LSB)
Slave Address:
equivalent to chip-
select line
Command Byte:
selects register you
are reading from
Slave Address: repeated
due to change in data-flow
direction
Data Bytes: reads from the
register set by the command
byte
S = Start condition Shaded = Slave transmission
P = Stop condition /// = Not acknowledged
Figure 1. SMBus Protocols
Figure 2. SMBus Write Timing Diagram
SMBCLK
AB CD
E
FG 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 = SLAVE PULLS SMBDATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION, DATA EXECUTED BY SLAVE
M = NEW START CONDITION
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