STW82102B datasheet(34/67 Pages) STMICROELECTRONICS

34 / 67 page

I2C bus interface

STW82102B

34/67

Doc ID 018516 Rev 2

9.1.2

START and STOP conditions

Figure 15.

START and STOP condition waveform

START condition

A START condition is identified by a HIGH to LOW transition of the data bus SDA while the

clock signal SCL is stable in the HIGH state. A Start condition must precede any command

for data transfer.

STOP condition

A STOP condition is identified by a transition of the data bus SDA from LOW to HIGH while

the clock signal SCL is stable in the HIGH state.. A STOP condition terminates

communications between the STW82102B and the Bus Master.

9.1.3

Byte format and acknowledge

Every byte (8 bits long) transferred on the SDA line must contain bits. Each byte must be

followed by an acknowledge bit. The MSB is transferred first.

An acknowledge bit indicates a successful data transfer. The transmitter, either master or

slave, releases the SDA bus after sending 8 bits of data. During the 9th clock pulse the

receiver pulls the SDA low to acknowledge the receipt of 8 bits of data.

Figure 16.

Byte format and acknowledge waveform

SCL

SDA

START

STOP

SCL

SDA

START

MSB

STOP

Acknowledgement

from receiver

STW82102B Datasheet(PDF) 34 Page - STMicroelectronics