TDA7540B datasheet(35/75 Pages) STMICROELECTRONICS

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TDA7540B

Functional description

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4.5.3

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.

4.5.4

Acknowledge

Indicates a successful data transfer. The transmitter will release the bus after sending 8 bits

of data. During the 9th clock cycle the receiver will pull the SDA line to LOW level to indicate

it receive the eight bits of data.

4.5.5

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.

4.5.6

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 TDA7540 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 59 defines the state of this address bit. So up to two devices

could be connected on the same bus. When PIN 59 is connected to VCC2 and a resistor at

PIN 55 versus ground of about 5,6k Ohm the address bit “1” is selected. In this case the AM

part doesn’t work. Otherwise the address bit “0” is selected (FM and AM is working).

Therefor 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 TDA7540 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

TDA7540 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.

4.5.7

Write operation

Following a START condition the master sends a slave address word with the R/W bit set to

"0". The device will generate an "acknowledge" after this first transmission and will wait for a

second word (the word address field). This 8-bit address field provides an access to any of

the 64 internal addresses.

Upon receipt of the word address the TDA7540 slave device will respond with an

"acknowledge". At this time, all the following words transmitted to the TDA7540 will be

considered as Data. The internal address will be automatically incremented up to hex40 in

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