SAA2520 Datasheet, PDF(22/36 Page) NXP Semiconductors – Stereo filter and codec for MPEG layer 1 audio applications

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SAA2520 Datasheet, PDF (22/36 Pages) NXP Semiconductors – Stereo filter and codec for MPEG layer 1 audio applications

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Philips Semiconductors

Stereo ï¬lter and codec for MPEG layer 1

audio applications

Preliminary speciï¬cation

SAA2520

Bits D0 to D3 are copied directly to the corresponding

output pins/mode flip-flop.

For HOLDCLKOK = logic 1. When CLKOK drops it will

remain LOW until set by an encode/decode mode, sample

frequency, external 256FS or bit rate index change.

Note 1.

When D0 = logic 1 (default) I2S mode is selected. For D0

= logic 0 the alternative mode is selected. The setting of D0

remains dormant until activated by the occurrence of

FRESET.

ALLOCATION/SCALE FACTOR INFORMATION (LTCNT1 =

LOGIC 0, LTCNT0 = LOGIC 1)

For encoding, the allocation and scale factor arrays can be

filled using this mode. To completely fill the allocation array

16 complete transfers of 16-bits are required. After the first

transfer of allocation information a check must be made to

determine when the SAA2520 is ready to receive the

remaining information. This will ensure synchronization

with the internal program of the SAA2520. Transfer of the

allocation information is completed by sending the internal

settings.

This is then followed by the scale factor information.

In the event that only internal settings information is sent,

then a default allocation of logic 0 will be assigned to all

sub-bands. If in addition no internal settings are sent then

the previous settings remain valid.

The allocation information is transferred in 4-bit units.

Each of these units contains the number of bits allocated

to the sub-band, MINUS 1, except in the case of a logic 0

value, which indicates that no bits are allocated to that

sub-band.

Scale factor information is transferred in units of 8-bits,

containing the 6-bit scale factor which is extended to 8-bits

by adding two logic 0âs at the most significant end.

In the case of stereo encoding the channels are indicated

by L (left) and R (right). This changes to I and II in the case

of 2 channel mono encoding.

Table 6 Allocation information format.

msb

B15

B11

bits

B14

B13

B10

Table 7 Scalefactor information format.

msb

B15

bits

................

lsb

B12

lsb

channel

L or I

R or II

L or I

R or II

sub-band

0 .. 30 (even)

1 .. 31 (odd)

channel

L or I

R or II

sub-band

0 .. 31

August 1993

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