I2C bus interface TDA7342
10/20
3 I
2
C bus interface
Data transmission from microprocessor to the TDA7342 and viceversa takes place thru the
2 wires I
2
C BUS interface, consisting of the two lines SDA and SCL (pull-up resistors to
positive supply voltage must be externally connected).
3.1 Data Validity
As shown in Figure 3, 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.
3.2 Start and Stop Conditions
As shown in Figure 5 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.
A STOP conditions must be sent before each START condition.
3.3 Byte Format
Every byte transferred to the SDA line must contain 8 bits. Each byte must be followed by an
acknowledge bit. The MSB is transferred first.
3.4 Acknowledge
The master (µP) puts a resistive HIGH level on the SDA line during the acknowledge clock
pulse (see Figure 5). The peripheral (audioprocessor) that acknowledges has to pull-down
(LOW) the SDA line during the acknowledge clock pulse, so that the SDA line is stable LOW
during this clock pulse.
The audioprocessor 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.
3.5 Transmission without Acknowledge
Avoiding to detect the acknowledge of the audioprocessor, the P can use a simplier
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 and
decreases the noise immunity.
