STA328 datasheet(9/41 Pages) STMICROELECTRONICS

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STA328

6.1 COMMUNICATION PROTOCOL

6.1.1

Data Transition or change

Data changes on the SDA line must only occur when the SCL clock is low. SDA transition while the clock

is high is used to identify a START or STOP condition.

6.1.2

Start Condition

START is identified by a high to low transition of the data bus SDA signal while the clock signal SCL is

stable in the high state. A START condition must precede any command for data transfer.

6.1.3

Stop Condition

STOP is identified by a low to high transition of the data bus SDA signal while the clock signal SCL is stable

in the high state. A STOP condition terminates communication between STA328 and the bus master.

6.1.4

Data Input

During the data input the STA328 samples the SDA signal on the rising edge of clock SCL. For correct

device operation the SDA signal must be stable during the rising edge of the clock and the data can

change only when the SCL line is low.

6.2 DEVICE ADDRESSING

To start communication between the master and the STA328, the master must initiate with a start condi-

tion. Following this, the master sends 8-bits (MSB first) onto the SDA line corresponding to the device

select address and read or write mode.

The 7 most significant bits are the device address identifiers, corresponding to the I2C bus definition. In

the STA328 the I2C interface uses a device addresse of 0x34 or 0011010x.

The 8th bit (LSB) identifies read or write operation, RW. This bit is set to 1 in read mode and 0 for write

mode. After a START condition the STA328 identifies the device address on the bus. If a match is found,

it acknowledges the identification on the SDA bus during the 9th bit time. The byte following the device

identification byte is the internal space address.

6.3 WRITE OPERATION

Following the START condition the master sends a device select code with the RW bit set to 0. The

STA328 acknowledges this and then the master writes the internal address byte.

After receiving the internal byte address the STA328 again responds with an acknowledgement.

6.3.1

Byte Write

In the byte write mode the master sends one data byte. This is acknowledged by the STA328. The master

then terminates the transfer by generating a STOP condition.

6.3.2

Multi-byte Write

The multi-byte write modes can start from any internal address. Sequential data byte writes will be written

to sequential addresses within the STA328.

The master generating a STOP condition terminates the transfer.

6.4 READ OPERATION

6.4.1

Current Address Byte Read

Following the START condition the master sends a device select code with the RW bit set to 1. The

STA328 acknowledges this and then responds by sending one byte of data. The master then terminates

the transfer by generating a STOP condition.

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