TDA7333N datasheet(20/36 Pages) STMICROELECTRONICS

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Functional description

TDA7333N

20/36

Figure 9 describes the different states of the buffer with corresponding flags values:

This is the reset state, read (Rp) and write pointer (Wp) pointing at the same location 0.

The buffer is empty.

After the first buffer write operation, Wp points to the last written data (0, it is not

incremented) and the flag “bne” (buffer not empty) is set.

After next buffer write operation, Wp points to the last written data (3, incremented

address).

After buffer read operation, Rp points to incremented address (data to be read on the

next read cycle), following the Wp. As soon as Rp reaches the Wp (of value 3), it is not

incremented to 4 and flag “bne” is reset. Rp never goes ahead the Wp.

If the buffer is full (i.e. 24 blocks have been written before any read), flag “bfull” is set. If

no read operation is performed, on next write operation “bovf” (buffer overflow) is set,

and each subsequent write operation will overwrite the oldest data of the RAM buffer.

Rp is moved in front of the Wp.

If the whole content of the buffer has already been read, subsequent read operation will

always read the last written location - Rp never goes ahead the Wp.

3.8

Programming through serial bus interface

The serial bus interface is used to access the different registers of the chip. It is able to

handle both I2C and

SPI transfer protocols, the selection between the two modes is done thanks to the pin CSN:

–

if the pin CSN is high, the interface operates as an I2C bus.

–

if the pin CSN is asserted low, the interface operates as a SPI bus.

In both modes, the device is a slave, i.e the clock pin SCL_CLK is only an input for the chip.

Depending on the transfer mode, external pins have alternate functions as following:

13 registers are available with read or read/write access:

Table 6.

External pins alternate functions

Function in SPI mode (CSN=0)

Function in I2C mode (CSN=1)

SCL_CLK

CLK (serial clock)

SCL (serial clock)

SDA_DATAIN

DATAIN (data input)

SDA (data line)

SA_DATAOUT

DATAOUT (data output)

SA (slave address)

Table 7.

Registers description

Access

rights

Function

rds_int[7:0]

read/write

interrupt source setting, synch., bne information

rds_qu[7:0]

read

quality counter, actual block name

rds_corrp[7:0]

read

error correction status, buffer ovf information

rds_bd_h[7:0]

read

high byte of current RDS block

rds_bd_l[7:0]

read

low byte of current RDS block

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