SAA2520 Datasheet, PDF (25/36 Pages) NXP Semiconductors – Stereo filter and codec for MPEG layer 1 audio applications

Philips Semiconductors
Stereo filter and codec for MPEG layer 1
audio applications
Table 13 MODE identification.
msb
lsb
0
0
0
1
1
0
1
1
Ready-to-receive indicates whether the SAA2520 is ready
to receive allocation, scale factor or internal setting
transfers. This should be checked in order to synchronize
the transfer of such information.
In 2 channel mono decode mode the selected samples are
transferred to both output channels. The same occurs with
all samples in 1-channel mono decode mode. In both of
these instances the L and R filter output channels are
identical.
In decode mode the SYNC bit is logic 0 when the SAA2520
is unable to decode the sub-band frames. This will occur in
the following situations:
• with the loss of synchronisation
• when in correct allocation information is received for two
or more subsequent frames (SBEF was HIGH).
• when the URDA input pin is HIGH
In these situations the SAA2520 data output will be muted.
The SYNC bit will return to logic 1 as soon as the decoder
is resynchronized to the incoming sub-band data.
CLKOK indicates whether the 256FS clock corresponds to
specified sample frequency. The CLKOK bit is set to logic
1 after a change in sample frequency, operation mode or
EXT256FS setting. It drops to logic 0 as soon as the
256FS clock deviates from the nominal frequency by more
than approximately 0.2%. Return to logic 1 will only occur
automatically when the extended setting
CLKOK-hold-mode is logic 0.
The transparent bits are copied from the MPEG coded
signal.
The EMPHASIS indication is as defined in the internal
settings. It can be used to apply the correct de-emphasis.
Note: the two bytes of the status are 'sampled' at different
moments so the information may not result from the same
sub-band frame.
mode
stereo
joint stereo
2 channel mono
1 channel mono
Preliminary specification
SAA2520
output
L and R
L and R
I or II as selected
mono; no selection
August 1993
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