SAA7284ZP PHILIPS [NXP Semiconductors], SAA7284ZP Datasheet - Page 18

• Manufacturer Part Number: SAA7284ZP
• Description: Terrestrial digital sound decoder for conventional intercarrier PLL-IF systems
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
DIGITAL AUDIO INTERFACE IEC/EBU 958
Block structure
The output is grouped into a block of 192 consecutive
frames providing, for each channel the 192 channel status
data bits. The start of a block is designated by a special
sub-frame preamble.
Frame structure
Each frame is uniquely composed of two sub-frames.
The rate of transmission of frames corresponds exactly to
the source sampling frequency. In the 2-channel
operation, samples taken from both channels are
transmitted by time multiplexing in consecutive
sub-frames. Sub-frames related to Channel 1 (left or ‘A’
channel in stereophonic operation and primary channel in
monophonic operation) normally use preamble M.
However the preamble is changed to preamble B once
every 192 frames. This defines the block structure used to
organize the channel status information. Sub-frames of
Channel 2 (right or ‘B’ channel in stereophonic operation
and secondary channel in monophonic operation) always
use preamble W.
1996 Oct 24
handbook, full pagewidth
handbook, full pagewidth
Terrestrial digital sound decoder for
conventional intercarrier PLL-IF systems
0
M
MLB156
preamble
sync
channel 1
3
frame 191
4
logical 0 bits
W channel 2
11 12
Fig.6 Sub-frame structure.
S
B
L
B
Fig.5 Frame format.
sub-frame
start of block
channel 1 W channel 2 M
frame 0
18
audio sample word
Sub-frame structure
Each frame is divided into 32 time-slots numbered 0 to 31.
Time-slots 0 to 3 carry one of three permitted preambles.
These are used to affect synchronization of sub-frames,
frames and blocks.
Time-slots 4 to 27 carry the audio sample word in linear
two's complement representation. The most significant bit
is carried by time-slot 27.
Time-slot 28 carries the validity flag associated with the
audio sample word. This flag is set to logic 0 if the audio
sample is reliable. If set to logic 1 then the sample is
unreliable.
Time-slot 29 carries one bit of the user data channel.
In this application this is not used and so is set to logic 0.
Time-slot 30 carries one bit of the channel status word
associated with the audio channel transmitted in the same
sub-frame.
Time-slot 31 carries a parity bit such that time-slots 4 to 31
inclusive will carry an even number of ones and an even
number of zeros.
sub-frame
user data = logic 0
channel status
validity flag
channel 1 W
parity bit
frame 1
27
M
S
B
28
V U C P
channel 2
MLB155
Preliminary specification
31
SAA7284