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TDA7448

terface, consisting of the two lines SDA and SCL (pull-up resistors to positive supply voltage must be connected).

4.1 Data Validity

As shown in fig. 8, the data on the SDA line must be stable during the high period of the clock. The HIGH and

LOW state of the data line can only change when the clock signal on the SCL line is LOW.

4.2 Start and Stop Conditions

As shown in fig. 9 a start condition is a HIGH to LOW transition of the SDA line while SCL is HIGH. The stop

condition is a LOW to HIGH transition of the SDA line while SCL is HIGH.

4.3 Byte Format

Every byte transferred on the SDA line must contain 8 bits. Each byte must be followed by an acknowledge bit.

The MSB is transferred first.

4.4 Acknowledge

The master (

µP) puts a resistive HIGH level on the SDA line during the acknowledge clock pulse (see fig. 10). The

peripheral (audio processor) that acknowledges has to pull-down (LOW) the SDA line during this clock pulse.

The audio processor which has been addressed has to generate an acknowledge after the reception of each

byte, otherwise the SDA line remains at the HIGH level during the ninth clock pulse time. In this case the master

transmitter can generate the STOP information in order to abort the transfer.

4.5 Transmission without Acknowledge

Avoiding to detect the acknowledge of the audio processor, the

µP can use a simpler transmission: simply it

waits one clock without checking the slave acknowledging, and sends the new data.

This approach of course is less protected from misworking.

SDA

SCL

DATA LINE

STABLE, DATA

VALID

CHANGE

DATA

ALLOWED

D99AU1031

SCL

SDA

START

STOP

D99AU1032

SCL

1

MSB

23789

SDA

START

ACKNOWLEDGMENT

FROM RECEIVER

D99AU1033