ALED7709ATR datasheet(40/63 Pages) STMICROELECTRONICS

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The ALED7709x do not generate acknowledge if the VIN supply is below the undervoltage Lockout threshold or

if EN pin is driven LOW; these conditions are not allowing the I2C block to be active and so able to reply to any

master request.

Figure 22. Acknowledge on the I2C bus

8.2.5

Interface protocol

The interface protocol is composed of:

•

Start condition (START)

•

Device address (7-bit) + R/W bit (read = 1 / write = 0)

•

Sequence of N data packet (1 byte + acknowledge)

•

Stop condition (STOP)

The register address byte determines the first register in which the read or write operation takes place. When

the read or write operation is finished, the internal register address pointer is automatically incremented allowing

multiple register writing or reading.

Figure 23. Interface protocol

Device

addr[6:0]

addr[7:0]

Data[7:0]

8.2.5.1

Writing to a single register

Writing to a single register starts with a START condition followed by the 7-bit device address of ALED7709x, the

8th bit of the byte is the R/W bit, which is 0 for writing operations.

Then the master waits for ALED7709x acknowledge. Then the 8-bit address of the register is sent to ALED7709x

and it is also followed by an acknowledge pulse. The last transmitted byte is the data to be written into the

STOP condition, and the communication is over.

Figure 24. Writing to a single register

Device

addr[6:0]

addr[7:0]

Data[7:0]

ALED7709

I2C serial bus

DS14214 - Rev 1

page 40/63

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