TDA7546 datasheet(35/68 Pages) STMICROELECTRONICS

35 / 68 page

TDA7546

Functional description

35/68

An address reset of the RAM buffer can be performed by writing a 1 to “ar_res” bit in rds_int

Figure 10 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.

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