TDA7541B Datasheet, PDF (40/77 Pages) STMicroelectronics – AM/FM car radio tuner IC with stereo decoder and intelligent selectivity system

Functional description
TDA7541B
Data transition
Data transition on the SDA line must only occur when the clock SCL is LOW. SDA transitions
while SCL is HIGH will be interpreted as START or STOP condition.
Start condition
A start condition is defined by a HIGH to LOW transition of the SDA line while SCL is at a
stable HIGH level. This "START" condition must precede any command and initiate a data
transfer onto the bus. The device continuously monitors the SDA and SCL lines for a valid
START and will not response to any command if this condition has not been met.
Stop condition
A STOP condition is defined by a LOW to HIGH transition of the SDA while the SCL line is at
a stable HIGH level. This condition terminates the communication between the devices and
forces the bus-interface of the device into the initial condition.
Acknowledge
Indicates a successful data transfer. The transmitter will release the bus after sending 8 bits
of data. During the 9^th clock cycle the receiver will pull the SDA line to LOW level to indicate
it receives the eight bits of data.
Data transfer
During data transfer the device samples the SDA line on the leading edge of the SCL clock.
Therefore, for proper device operation the SDA line must be stable during the SCL LOW to
HIGH transition.
Device addressing
To start the communication between two devices, the bus master must initiate a start
instruction sequence, followed by an eight bit word corresponding to the address of the
device it is addressing.
The most significant 6 bits of the slave address are the device type identifier.
The TDA7541B device type is fixed as "110001".
The next significant bit is used to address a particular device of the previous defined type
connected to the bus.
The state of the hardwired PIN 57 defines the state of this address bit. Using this feature up
to two devices could be connected on the same bus. When PIN 57 is connected to VCC via
an external resistor of about 82 kΩ the address bit "1" is selected. Please note: in this case
the AM part doesn't work. Otherwise the address bit "0" is selected (FM and AM is working).
Therefore a double FM tuner concept is possible.
The last bit of the start instruction defines the type of operation to be performed:
– When set to "1", a read operation is selected
– When set to "0", a write operation is selected
The TDA7541B connected to the bus will compare their own hardwired address with the
slave address being transmitted, after detecting a START condition. After this comparison,
the TDA7541B will generate an "acknowledge" on the SDA line and will do either a read or a
write operation according to the state of R/W bit.
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Doc ID 16048 Rev 1