TDA7546 Datasheet, PDF (56/68 Pages) STMicroelectronics – Multichip module for TMC tuner applications

Software specifications
TDA7546
6.3.2
I²C transfer mode
This interface consists of three lines: a serial data line (SDA), a bit clock (SCL), and a slave
address select (SA).
The interface is capable of operating up to 400kbits/s. If during the setup the system clock
fsys is smaller then 8.55MHz, then the max. I²C speed decreases linear (e.i. if fsys =
4.275MHz then the maximum I²C speed is 200 kbits/s for setup).
Data transfers follow the format shown in After the START condition (S), a slave address is
sent. The address is 7 bits long followed by an eighth bit which is a data direction bit (R/_W).
A zero indicates a transmission (WRITE), a one indicates a request for data (READ).
The slave address of the chip is set to 001000S, where S is the least significant bit of the
slave address set externally via the pin SA_DATAOUT. This allows to choose between two
addresses in case of conflict with another device of the radio set.
Each byte has to be followed by an acknowledge bit (SDA low).
Data is transferred with the most significant (MSB) bit first.
A data transfer is always terminated by a stop condition (P) generated by the master.
Figure 12. I²C data transfer
SDA
SCL
S
START
CONDITION
1-7 8 9
ADDRESS R/W ACK
1-7 8 9
DATA
ACK
1-7 8
DATA
9
P
ACK/ACK STOP
CONDITION
Write transfer
Figure 13. I²C write transfer
S Slave address W A rds_int A rds_bd_ctrl A sinc4reg A testreg A P
from master to slave
from slave to master
S = start condition
W = write mode
Slave address = 001000S ( where S is the level of the pin
A = acknowledge bit
P = stop condition
SA_DATAOUT)
9 registers are available with write access (please refer to the relevant sections for the
meaning of each bit).
To write registers, the external master must initiate the write transfer as described above,
then send the data to be written, and terminate the transfer by generating a stop condition.
The transfer can be terminated after having written one, two, three, four (Figure 13), or five
bytes.
56/68