TDA1315 Philips Semiconductors, TDA1315 Datasheet - Page 13

• Manufacturer Part Number: TDA1315
• Description: Digital audio input/output circuit DAIO
• Manufacturer: Philips Semiconductors

Philips Semiconductors
In this instance, synchronization of Q-channel frames must
be maintained by the microcontroller. It is recommended to
read decoded Q-channel data in groups of 12 bytes
otherwise synchronization of subcode frames may be lost
quickly. Again, the data transfer is supported by the signal
at pin UDAVAIL. This time it goes LOW when there is at
least one full frame (12 bytes) of Q-channel data in the
buffer, and goes HIGH again, when less than 12 bytes are
in the buffer. This is illustrated in Fig.4.
An initial synchronization can be obtained by clearing the
buffer via the control register, then start counting bytes
modulo 12. Again, the LSB is sent first on the user
interface, i.e. the first byte of a Q-channel frame will be
output as follows:
1. Bit sent = Q8.
2. Bit sent = Q7.
3. Bit sent = Q6.
4. Bit sent = Q5.
5. Bit sent = Q4.
6. Bit sent = Q3.
7. Bit sent = Q2.
8. Bit sent = Q1.
Writing to the buffer is disabled when the FIFO is full. It is
re-enabled when there is at least 1 byte free. Any data
overrun condition will be flagged as an error in the status
register. When this has occurred, the appropriate strategy
for data handling is decided by the microcontroller. It can,
for example, clear the buffer via the control register,
thereby discarding all remaining data, or it can start
reading data rapidly. Clearing the buffer turns UDAVAIL
HIGH. The response to reading data is the same as
described previously, depending on the mode of reception,
i.e. Q-channel decoding or normal message protocol.
For the period that the user data register is selected, the
microcontroller has to poll UDAVAIL each time after
reading one byte in normal mode, or 12 bytes in Q-channel
mode. Possible actions by the microcontroller are as
follows:
1995 Jul 17
If UDAVAIL = 0: reading the next byte in normal mode or
the next 12 bytes in Q-channel mode.
If UDAVAIL = 1: either wait until UDAVAIL goes LOW
and continue reading user data byte(s), or write data,
read other data or deselect the TDA1315H by foreign
addressing.
– Remark: it is allowed to address the TDA1315H for
Digital audio input/output circuit (DAIO)
reading user data again when UDAVAIL is still HIGH,
but it is forbidden to apply clock pulses until UDAVAIL
has gone LOW.
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Remark: whenever the buffer is empty (UDAVAIL = 1),
normally zeroes will be read, even when the
microcontroller tries to read more bytes. Doing so,
however, poses the risk of reading not all zeroes. In this
event new data is stored in the buffer during reading,
thereby losing synchronization. To assure correct
information will be read, the microcontroller should
perform an addressing sequence (not necessarily to the
TDA1315H), whenever an UDAVAIL HIGH is detected
before reading further.
Transmit mode
User data bits are supplied by the microcontroller in the
general message format only, Q-channel encoding is not
available in the TDA1315H. Again, UDAVAIL can be used
to synchronize transfers. It goes HIGH, when the buffer
contains at least 112 bytes, and goes LOW only when
there are no more than 16 bytes in the buffer. This is
illustrated in Fig.5.
Thus, after UDAVAIL has gone LOW, the microcontroller
can write a full CD subcode frame (96 data bytes plus
2 synchronization bytes) to the buffer without needing to
poll the state of pin UDAVAIL. In the event that no data are
available in the buffer, the user data bits in the IEC output
signal will be set to zero. Should the microcontroller
attempt to write more data than the buffer can hold, writing
will be disabled and the data overrun bit set in the status
register. Any bytes that have been transferred but not
written into the buffer are lost.
Four zero bits will be inserted automatically between user
data bytes (information units). The gap between
messages can be achieved by writing a single byte
containing all zeroes to the buffer.
U
The user interface is an interface between the data
processing sections of the TDA1315H and the user. The
basic mode of operation (control by a host or stand-alone
operation) is selected by pin CTRLMODE. In the host
mode, all data, control and status information is, in
principle, exchanged with a microcontroller although the
device configuration can also be changed by pin control.
Up to 2 TDA1315Hs can be used on the same user
interface by setting different device addresses via the
LADDR pin. In the stand-alone mode (receive only), no
microcontroller is needed because important information is
brought out to pins FS32, FS44 and FS48, being an
indication of sample frequency, copyright protection
(COPY) (see Chapter “References”[2]) and use of
pre-emphasis (DEEM).
SER INTERFACE
Product specification
TDA1315H