STA308

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2.1 COMMUNICATION PROTOCOL

2.1.1 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.

2.1.2 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.

2.1.3 Stop Condition

STOP is identified by 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 STA308 and the bus master.

2.1.4 Data Input

During the data input the STA308 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.

2.2 DEVICE ADDRESSING

To start communication between the master and the STA308, the master must initiate with a start condition.

Following this, the master sends onto the SDA line 8-bits (MSB first) 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

STA308 the I2C interface has two device addresses depending on the SA pin configuration, 0x30 or 0011000x

when SA = 0, and 0x32 or 0011001x when SA = 1.

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 STA308 identifies on the bus the device address and if a match is found, it acknowl-

edges the identification on SDA bus during the 9th bit time. The byte following the device identification byte is

the internal space address.

2.3 WRITE OPERATION

Following the START condition the master sends a device select code with the RW bit set to 0. The STA308

acknowledges this and the writes for the byte of internal address. After receiving the internal byte address the

STA308 again responds with an acknowledgement.

2.3.1 Byte Write

In the byte write mode the master sends one data byte, this is acknowledged by the STA308. The master then

terminates the transfer by generating a STOP condition.

2.3.2 Multi-byte Write

The multi-byte write modes can start from any internal address. The master generating a STOP condition ter-

minates the transfer.