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SS8018

Write Byte Format

S

ADDRESS

WR

ACK

COMMAND

ACK

DATA

ACK

P

7 bits

8 bits

8 bits

1

Slave Address: equivalent 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)

Read Byte Format

S

ADDRESS

WR

ACK

COMMAND

ACK

S

ADDRESS

RD

ACK

DATA

///

P

7 bits

8bits

7bits

8 bits

Slave Address: equivalent 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

Send Byte Format

S

ADDRESS

WR

ACK

COMMAND

ACK

P

7 bits

8 bits

Command Byte: sends command with no data , usually used for one-shot command

Receive Byte Format

S

ADDRESS

RD

ACK

DATA

///

P

7 bits

8 bits

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 Shaded = Slave transmission P = Stop condition /// = Not acknowledged

Figure 3. SMBus Protocols

Rev.2.01 6/06/2003