TDA7309
I2C BUS INTERFACE
Acknowledge
µ
Data transmission from microprocessor to the
TDA7313 and viceversa takes place thru the 2
wires I2C BUS interface, consisting of the two
lines SDA and SCL (pull-up resistors to positive
supply voltage must be connected).
The master ( P) puts a resistive HIGH level on the
SDA line during the acknowledge clock pulse (see
fig. 13). The peripheral (audioprocessor) that ac-
knowledges has to pull-down (LOW) the SDA line
during the acknowledge clock pulse, so that the
SDAline is stable LOWduringthis clock pulse.
The audioprocessor which has been addressed
has to generate an acknowledge after the recep-
tion 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 gen-
erate the STOP information in order to abort the
transfer.
Data Validity
As shown in fig. 11, 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.
Start and Stop Conditions
As shown in fig. 12 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 tran-
sition of the SDA line while SCL is HIGH.
Transmissionwithout Acknowledge
Avoiding to detect the acknowledge of the audio-
processor, the µP can use a simplier transmis-
sion: simply it waits one clock without checking
the slave acknowledging, and sends the new
data.
Byte Format
Every byte transferred on the SDA line must con-
tain 8 bits. Each byte must be followed by an ac-
knowledge bit. The MSB is transferred first.
This approach of course is less protected from
misworking and decreases the noise immunity.
2
Figure 11:
Data Validity on the I CBUS
2
Figure 12:
Timing Diagram of I CBUS
2
Figure 13:
Acknowledgeon the I CBUS
6/12
STMICROELECTRONICS [ ST ]
