Datasheet

Slave Address 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).
Figure 2a. SMBus Protocol: Write Byte Format
Slave Address 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.
Figure 2b. SMBus Protocol: Read Byte Format
Data byte: Reads data
from the register com-
manded by the last
read-byte or write-byte
transmission; also
used for SMBus alert
response return address.
Figure 2c. SMBus Protocol: Receive Byte Format
S = Start condition Shaded = Slave transmission WR = Write = 0
P = Stop condition ACK = Acknowledged = 0 RD = Read =1
A = Not acknowledged = 1
Fan-Speed Regulators and Monitors
with SMBus/I
2
C-Compatible Interface
Maxim Integrated 7
MAX6650/MAX6651
COMMANDS
8 bits
PACKDATA
8 bits
WR
0
ACKADDRESS
7 bits
ACK
COMMANDS
8 bits
WR
0
ACKADDRESS
7 bits
ACK
S P
A
DATA
8 bits
RD
1
ADDRESS
7 bits
ACK
S P
A
DATA
8 bits
RD
1
ADDRESS
7 bits
ACK
Slave Address