STTS751

SMBus interface

Doc ID 16483 Rev 5

11/36

3.2

WRITE byte

The WRITE byte protocol is used to write one byte of data to the registers as shown in

Table 4. The gray data is sent by the STTS751 while the white data is sent by the host.

3.3

READ byte

The READ byte protocol is used to read one byte of data from the registers as shown in

Table 5.

3.4

SEND byte

The SEND byte protocol is used to set the internal address register to the correct address. It

sends a register address with no data (see Table 6). The SEND byte can be followed by the

RECEIVE byte protocol described below in order to read data from the register.

3.5

RECEIVE byte

The RECEIVE byte protocol is used to read data from the register when the internal register

address pointer is known (see Table 7). This can be used for consecutive reads of the same

register.

Table 4.

SMBus WRITE byte protocol

Start

Slave address

WR

ACK

Register

address

ACK

Data

ACK

Stop

1 bit

7 bits

1 bit

1 bit

8 bits

1 bit

8 bits

1 bit

1 bit

Table 5.

SMBus READ byte protocol

Start

Slave address

WR

ACK

Register

address

ACK

Start

Slave address

RD

ACK

Data

NACK Stop

1 bit

7 bits

1 bit

1 bit

8 bits

1 bit

1 bit

7 bits

1 bit

1 bit

8 bits

1 bit

1 bit

Table 6.

SMBus SEND byte protocol

Start

Slave address

WR

ACK

Register address

ACK

Stop

1 bit

7 bits

1 bit

1 bit

8 bits

1 bit

1 bit

Table 7.

SMBus RECEIVE byte protocol

Start

Slave address

RD

ACK

Data

NACK

Stop

1 bit

7 bits

1 bit

1 bit

8 bits

1 bit

1 bit