L7292 datasheet(24/60 Pages) STMICROELECTRONICS

24 / 60 page

I2C interface

L7292

24/60

DocID028601 Rev 1

Figure 6. I2C protocol: bit order (MSB first), ACK bit, Start and Stop condition

8.3

I2C device operation

The device supports the I2C protocol. Any device that sends data on to the bus is defined to

be a transmitter, and any device that reads the data to be a receiver. The device that

controls the data transfer is known as the bus master, and the other as the slave device.

A data transfer can only be initiated by the bus master, which will also provide the serial

clock for synchronization. The device is always a slave in all communications.

8.3.1

Start condition

The start is identified by a falling edge of Serial Data (SDA) while the Serial Clock (SCL) is

stable in the high state. A Start condition must precede any data transfer command. The

device continuously monitors (except during a write cycle) Serial Data (SDA) and the Serial

Clock (SCL) for a Start condition, and will not respond unless one is given.

8.3.2

Stop condition

The Stop is identified by a rising edge of Serial Data (SDA) while the Serial Clock (SCL) is

stable and driven high. A Stop condition terminates communication between the device and

the bus master. A Read command that is followed by NoACK can be followed by a Stop

condition.

The Stop condition can be substituted by a repeated Start condition. In this case the bus

remains busy and another communication can start immediately.

8.3.3

Acknowledge bit (ACK)

The acknowledge bit is used to indicate a successful byte transfer. The bus transmitter,

whether it is the bus master or slave device, releases Serial Data (SDA) after sending eight

bits of data. During the 9th clock pulse period, the receiver pulls Serial Data (SDA) low to

acknowledge the receipt of the eight data bits.

8.3.4

Data input

During data input, the device samples Serial Data (SDA) on the rising edge of the Serial

Clock (SCL). For the correct device operation, Serial Data (SDA) must be stable during the

rising edge of the Serial Clock (SCL), and the Serial Data (SDA) signal must change only

when the Serial Clock (SCL) is driven low.

L7292 Datasheet(PDF) 24 Page - STMicroelectronics