saa2520 NXP Semiconductors, saa2520 Datasheet - Page 22

• Manufacturer Part Number: saa2520
• Description: Stereo Filter And Codec For Mpeg Layer 1 Audio Applications
• Manufacturer: NXP Semiconductors

Philips Semiconductors
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) I
= logic 0 the alternative mode is selected. The setting of D0
remains dormant until activated by the occurrence of
FRESET.
A
LOGIC
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.
Table 6 Allocation information format.
Table 7 Scalefactor information format.
August 1993
LLOCATION
Stereo filter and codec for MPEG layer 1
audio applications
B15
B11
B7
B3
0, LTCNT0 =
msb
msb
B15
B7
/S
CALE
-
-
-
-
F
LOGIC
ACTOR
B14
B10
B6
B2
1)
I
NFORMATION
2
S mode is selected. For D0
................
................
bits
bits
-
-
-
-
(LTCNT1 =
B13
B9
B5
B1
-
-
-
-
22
lsb
B8
B0
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 0’s 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.
B12
lsb
B8
B4
B0
channel
channel
R or II
R or II
R or II
L or I
L or I
L or I
0 .. 30 (even)
0 .. 30 (even)
1 .. 31 (odd)
1 .. 31 (odd)
0 .. 31
0 .. 31
Preliminary specification
sub-band
sub-band
SAA2520