STA013 Datasheet, PDF (9/38 Pages) STMicroelectronics – MPEG 2.5 LAYER III AUDIO DECODER

STA013 - STA013B - STA013T
2.5 - STA013 Operation Mode
The STA013 can work in two different modes,
called Multimedia Mode and Broadcast Mode.
In Multimedia Mode, STA013 decodes the in-
coming bitstream, acting as a master of the data
communication from the source to itself.
This control is done by a specific buffer manage-
ment, controlled by STA013 embedded software.
The data source, by monitoring the DATA_REQ
line, send to STA013 the input data, when the
signal is high (default configuration).
The communication is stopped when the
DATA_REQ line is low.
In this mode the fractional part of the PLL is dis-
abled and the audio clocks are generated at
nominal rates. Fig. 9 describes the default
DATA_REQ signal behaviour.
Programming STA013 it is possible to invert the
polarity of the DATA_REQ line (register
REQ_POL).
Figure 9.
SOURCE STOPS TRANSMITTING DATA
SOURCE STOPS TRANSMITTING DATA
DATA_REQ
SOURCE SEND DATA TO STA013
D98AU913
In Broadcast Mode, STA013 works receiving a
bitstream with the input speed regulated by the
source. In this configuration the source has to
guarantee that the bitrate is equivalent to the
nominal bitrate of the decoded stream.
To compensate the difference between the nomi-
nal and the real sampling rates, the STA013 em-
bedded software controls the fractional PLL op-
eration. Portable or Mobile applications need
normally to operate in Broadcast Mode. In both
modes the MPEG Synchronisation is automatic
and transparent to the user. To operate in Multi-
media mode, the STA013, pin nr. 8, SCR-INT
must be connected to VDD on the application
board.
2.6 - STA013 Decoding States
There are three different decoder states: Idle,
Init, and Decode. Commands to change the de-
coding states are described in the STA013 I²C
registers description.
Idle Mode
In this mode the decoder is waiting for the RUN
command. This mode should be used to initialise
the configuration register of the device. The DAC
connected to STA013 can be initialised during
this mode (set MUTE to 1).
PLAY
X
X
MUTE
0
1
Clock State
Not Running
Running
PCM Output
0
0
Init Mode
"PLAY" and "MUTE" changes are ignored in this
mode. The internal state of the decoder will be
updated only when the decoder changes from the
state "init" to the state "decode". The "init" phase
ends when the first decoded samples are at the
output stage of the device.
Decode Mode
This mode is completely described by the follow-
ing table:
PLAY
0
0
1
1
MUTE
0
1
0
1
Clock State
PCM
Output
Decoding
Not Running 0
No
Running
0
No
Running Decoded Yes
Samples
Running
0
Yes
3 - I²C BUS SPECIFICATION
The STA013 supports the I²C protocol. This pro-
tocol defines any device that sends data on to the
bus as a transmitter and any device that reads
the data as a receiver. The device that controls
the data transfer is known as the master and the
others as the slave. The master always starts the
transfer and provides the serial clock for synchro-
nisation. The STA013 is always a slave device in
all its communications.
3. 1 - COMMUNICATION PROTOCOL
3.1.0 - Data transition or change
Data changes on the SDA line must only occur
when the SCL clock is low. SDA transition while
the clock is high are used to identify START or
STOP condition.
3.1.1 - Start condition
START is identified by a high to low transition of
the data bus SDA signal while the clock signal
SCL is stable in the high state.
A START condition must precede any command
for data transfer.
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