An22 – Cirrus Logic AN22 User Manual
Page 3
AN22
AN22REV2
3
for each channel and one to indicate the beginning
of a channel status block (which is also channelA).
To distinguish the preambles from arbitrary data
patterns, the preambles contain two biphase-mark
violations. Biphase-mark data is required to transi-
tion at every bit period, but each preamble violates
that requirement twice. In Figure 3 each bit bound-
ary, indicated by the dashed lines, contains a tran-
sition in the biphase data. Each preamble shown in
Figure 4 has two bit boundaries with no transition,
which enables the receiver to recognize the data as
a preamble.
Table 1. Preambles
Biphase Patterns
Channel
X
11100010 or 00011101
Ch. A
Y
11100100 or 00011011
Ch. B
Z
11101000 or 00010111
Ch. A & C.S. Block Start
Preamble X
Preamble Y
Preamble Z
1 1 1 0 1 0 0 0
1 1 1 0 0 0 1 0
1 1 1 0 0 1 0 0
Figure 4. Preamble Forms
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Cyclic redundancy check character
Reliability flags
Time of day code
(32-bit binary)
Local sample address code
(32-bit binary)
Alphanumeric channel destination data
Alphanumeric channel origin data
Reserved
0
1
2
3
4
5
6
7
byte/bit
block
bit
7
15
23
31
39
55
87
119
151
183
191
PRO=1
Audio
Emphasis
Lock
Fs
Channel Mode
User Bit Management
AUX Use
Word Length
Reserved
47
Reserved
Reference
Reserved
Reserved
Figure 5. Professional Channel Status Block Structure