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TC1321
DS21387C-page 8
2010 Microchip Technology Inc.
FIGURE 3-1:
SMBus/I2C Protocols.
SAddress
R/W
ACK
Command
ACK
Data
ACK
P
8-Bits
0
1
7-Bits
8-Bits
Slave Address
Command Byte: selects
which register you are
writing to.
Data Byte: data goes
into the register set
by the command byte.
Write 1-Byte Format
S
Address
R/W
ACK
Command
ACK
Data
ACK
Data
ACK
P
8-Bits
7-Bits
8-Bits
Slave Address
Command Byte: selects
which register you are
writing to.
Data Byte: data goes
into the register set
by the command byte.
Write 2-Byte Format
Read 1-Byte Format
S
Address
R/W
ACK
Command
ACK
S
Address
R/W ACK Data
NACK
P
7-Bits
8-Bits
7-Bits
8-Bits
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.
Read 2-Byte Format
S
Address
R/W
ACK
Command
ACK
S
Address
R/W ACK Data
ACK
NACK
P
Data
7-Bits
8-Bits
7-Bits
8-Bits
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.
Receive 1-Byte Format
S
Address
R/W ACK
Data
NACK
P
7-Bits
8-Bits
Data Byte: reads data from
the register commanded by
the last read-byte or write-
byte transmission.
S = START Condition
P = STOP Condition
Shaded = Slave Transmission
Receive 1-Byte Format
S
Address
R/W ACK
Data
ACK
P
7-Bits
8-Bits
Data Byte: reads data from
the register commanded by
the last read-byte or write-
byte transmission.
S = START Condition
P = STOP Condition
Shaded = Slave Transmission