TDA7561

I2C bus

Doc ID 8326 Rev 6

17/27

6

I2C bus

6.1

I2C programming/reading sequence

A correct turn on/off sequence respectful of the diagnostic timings and producing no audible

noises could be as follows (after battery connection):

●

Turn-on: (Standby out + Diag enable) --- 500 ms (min) --- Muting out

●

Turn-off: Muting in --- 20 ms --- (Diag disable + Standby in)

●

Car radio installation: Diag enable (write) --- 200 ms --- I2C read (repeat until All faults

disappear).

●

Offset test: Device in Play (no signal) -- Offset enable - 30 ms - I2C reading (repeat I2C

reading until high-offset message disappears).

6.2

I2C bus interface

Data transmission from microprocessor to the TDA7561 and viceversa takes place through

the 2 wires I2C bus interface, consisting of the two lines SDA and SCL (pull-up resistors to

positive supply voltage must be connected).

6.2.1

Data validity

As shown by Figure 24, 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.

6.2.2

Start and stop conditions

As shown by Figure 25 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.

6.2.3

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.