TDA7703

Function description

Rev 1

11/32

2.12

IO interface pins

The TDA7703 has the following IO pins:

All the inputs are voltage-tolerant up to 3.5 V . The outputs can drive currents up to 0.5 mA

from the internal 3.3 V supply line.

2.13

Serial interface

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

parameters can be read out.

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

radio µP through the serial interface, which allow to simplify the operations carried out in the

main µP. The high level commands include among others:

●

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

●

start seek (the seek operation can be carried out by the TDA7703 in a completely

autonomous fashion).

The serial bus communication configuration is set by forcing pin 29 (BUSSET) to ground

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

The voltage level forced to pin 29 must be released to start the system operation a suitable

The status of pin 29 during the reset phase can be set to low by not forcing any voltage on it

from outside, as a 50 k

Ω internal pull-down resistors is present.

To make sure the boot mode 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 then for an

an acknowledge after any 8-bit transmission.

A "write" communication example is shown in the figure below, for an unspecified number of

data bytes (see Communication Protocol Manual for frame structure description):

Figure 3.

SDA

pin 26

serial communication with µP

SCL

pin 27

serial communication with µP

BUSSET

pin 29

serial communication with µP

RSTN

pin 30

reset pin driven by µP

ACK

data

STOP

clk1

clk2

…

clk8

clk9

clk1

clk2

START

ACK

d7

d6

address

a0

…

d0

…

clk8

clk9

a7

a6

…

SCL

SDA