saa7282 NXP Semiconductors, saa7282 Datasheet - Page 12

• Manufacturer Part Number: saa7282
• Description: Terrestrial Digital Sound Decoder Tdsd2
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Channel coding
Time-slots are encoded as biphase mark data. Each bit
transmitted is represented by a symbol comprising two
consecutive binary states. The first state of a symbol is
always different from the second state of the previous
symbol. The second state of the symbol is identical to the
first if the bit being transmitted is logic 0, however it is
different if the bit is logic 1 (see Table 7).
Table 7 Channel coding.
The preambles preceding each digital audio sample are used to indicate the beginning of a sample as follows:
Channel status
The channel status information is organized in 192-bit words. The first bit of each word is carried in the frame with
Preamble B. The 192-bit word is organized into sections as shown in Table 9.
Table 9 Channel status codes.
July 1993
Preamble B indicates the start of Channel A data and the beginning of a block
Preamble M indicates the start of Channel A data but not the beginning of a block
Preamble W indicates the start of Channel B data.
Terrestrial Digital Sound Decoder (TDSD2)
30 to 191
Preceding state
16 to 19
20 to 23
24 to 27
Transmitted bit
8 to 15
28, 29
BIT
3, 4
6, 7
0
1
2
5
0
1
00110001
CODE
all 0s
0000
0000
1100
00
11
00
00
0
0
1
0
11
10
0
Channel coding
consumer
sound data
digital copy permitted
indicates digital de-emphasis switched in
indicates digital de-emphasis switched out
category code
source code (don't care)
channel number (don't care)
sampling frequency (32 kHz)
clock accuracy (level II)
00
01
1
12
Preambles
Preambles are specific patterns providing synchronization
and identification of the sub-frames and blocks. A set of
three preambles is used. These preambles are transmitted
in the time allocated to four time-slots and are represented
by eight successive states. The first state of the preamble
is always different from the second state of the previous
symbol. Depending on this state the preambles are as
shown in Table 8.
Table 8 Preambles.
Preceding state
Preamble
DESCRIPTION
W
M
B
11101000
11100010
11100100
0
Channel coding
Product specification
SAA7282
00010111
00011101
00011011
1