TDA7540N datasheet(38/76 Pages) STMICROELECTRONICS

38 / 76 page

Functional description

TDA7540N

38/76

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 TDA7540N 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 TDA7540N 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.

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 TDA7540N slave device will respond with an

"acknowledge". At this time, all the following words transmitted to the TDA7540N will be

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

page mode. Than again subaddresse hex60 has to be transmitted for following registers

above 32.

After each word receipt the TDA7540N will answer with an "acknowledge".

Read operation

If the master sends a slave address word with the R/W bit set to "1", the TDA7540N will

transit one 8-bit data word. This data word includes the following informations:

bit0 (ISS filter, 1 = ON, 0 = OFF)

bit1 (ISS filter bandwidth, 1 = 80kHz, 0 = 120kHz)

bit2 (STEREO,1 = STEREO, 0 = MONO)

bit3 (1 = PLL is locked in , 0 = PLL is locked out).

bit4 (fieldstrength indicator, 1 = lower as softmute threshold, 0 = higher as softmute

threshold)

bit5 (adjacent channel indicator, 1 = adjacent channel present, 0 = no adjacent

channel)

bit6 (deviation indicator, 1 = strong overdeviation present, 0 = no strong overdeviation)

bit7 (deviation indicator, 1 = overdeviation present, 0 = no overdeviation)

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