TDA7786 datasheet(22/54 Pages) STMICROELECTRONICS

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Function description

TDA7786, TDA7786M

22/54

DocID026122 Rev 5

2.17

Serial control interface

The device is controlled via I2C.

Through serial bus the processing parameters can be modified and the signal quality

parameters and the RDS information can be read out.

The operation of the device is handled mainly through high level commands sent by the car-

radio microprocessor through the serial interface, which allows simplification of the

operations carried out in the microprocessor itself. The high level commands include among

others:



change frequency (which allows to avoid computing the PLL divider factors)



change band;



start seek (the seek operation can be carried out by the TDA7786x in a completely

autonomous fashion);



RDS seek/search (jumps to AF and quality measurements are automatically

sequenced).

2.17.1

Serial interface / boot mode

The device possesses two different I2C addresses: 0xC2/C3 and 0xC8/C9. The

configuration is chosen by applying the proper voltage at the exit from reset to the pins

indicated in Table 9. The configuration is latched (e.g. made effective) when the RSTN line

transitions from low to high (when RSTN is low, the IC is in reset mode).

The voltage level forced to the boot pins must be released to start the system operation a

suitable time after the RSTN line has gone high. The list of configurations is shown in the

following table:

The status of these pins during the reset phase can be set to:



High: through external <10 kΩ resistors tied to 3.3V



Low: by not forcing any voltage on them from outside, as 50 kΩ internal pull-down

resistors are present inside the device.

To make sure the I2C address is correctly latched up at start-up, it is advisable to keep the

RSTN line low until the IC supply pins have reached their steady state, and further keep it

low for an additional time Treset.

Table 9. 64-pin package boot mode configuration

SAI_AUDIO_DO

pin 39

RDS INT

pin 32

BUS mode

I2C Address = 0xC2

I2C Address = 0xC8

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