TDA7439

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4

Data transmission from the microprocessor to the TDA7439 and vice versa takes place

Pull-up resistors to the positive supply voltage must be used (there are no internal pull-ups).

4.1

Data validity

The data on the SDA line must be stable during the high period of the clock as shown in

Figure 12. SDA is allowed to change only when SCL is low.

4.2

Start and stop conditions

As shown in Figure 13 a start condition is a high to low transition of SDA while SCL is high.

The stop condition is a low to high transition of SDA while SCL is high.

4.3

Byte format

Every byte transferred on the SDA line must contain 8 bits. The MSB is transferred first.

There is also provision for an acknowledge bit to follow each byte to indicate that the data

has been received.

4.4

Acknowledge

The master (µP) puts a resistive high level on SDA during the acknowledge clock pulse (see

Figure 14). 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

Suppressing the audio processor acknowledge detection enables the µP to use a simpler

transmission: it simply waits for one clock, without checking the slave acknowledging, and

then sends the new data.

This approach has, of course, less protection from transmission errors.