STA015T datasheet(15/56 Pages) STMICROELECTRONICS

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STA015

5.1.4 Data input

During the data input the STA015 samples the SDA signal on the rising edge of the clock SCL. For correct

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

change only when the SCL line is low.

5.2 DEVICE ADDRESSING

To start communication between the master and the STA015, the master must initiate with a start condi-

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

lect address and read or write mode. The 7 most significant bits are the device address identifier,

corresponding to the I2C bus definition. For the STA015 these are fixed as 1000011.

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

After a START condition the STA015 identifies on the bus the device address and, if a match is found, it

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

identification byte is the internal space address.

5.3 WRITE OPERATION (see fig. 16)

Following a START condition the master sends a device select code with the RW bit set to 0. The STA015

acknowledges this and waits for the byte of internal address.

After receiving the internal bytes address the STA015 again responds with an acknowledge.

5.3.1 Byte write

In the byte write mode the master sends one data byte, this is acknowledged by STA015. The master then

terminates the transfer by generating a STOP condition.

5.3.2 Multibyte write

The multibyte write mode can start from any internal address. The transfer is terminated by the master

generating a STOP condition.

Figure 16. Write Mode Sequence

Figure 17. Read Mode Sequence

DEV-ADDR

ACK

START

D98AU825B

SUB-ADDR

ACK

DATA IN

ACK

STOP

BYTE

WRITE

DEV-ADDR

ACK

START

SUB-ADDR

ACK

DATA IN

ACK

STOP

MULTIBYTE

WRITE

DATA IN

ACK

DEV-ADDR

ACK

START

D98AU826A

DATA

NO ACK

STOP

CURRENT

ADDRESS

READ

DEV-ADDR

ACK

START

SUB-ADDR

ACK

DEV-ADDR

ACK

STOP

RANDOM

ADDRESS

READ

DATA

NO ACK

START

DEV-ADDR

ACK

START

DATA

ACK

DATA

ACK

STOP

SEQUENTIAL

CURRENT

READ

DATA

NO ACK

DEV-ADDR

ACK

START

SUB-ADDR

ACK

DEV-ADDR

ACK

SEQUENTIAL

RANDOM

READ

DATA

ACK

START

DATA

ACK

NO ACK

STOP

DATA

RW=

HIGH

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