mt9072av2 Zarlink Semiconductor, mt9072av2 Datasheet - Page 50

• Manufacturer Part Number: mt9072av2
• Description: Octal T1/e1/j1 Framer
• Manufacturer: Zarlink Semiconductor

5.2.2
The primary purpose for CRC-4 multiframing is to provide a verification of the current basic frame alignment,
although it can also be used for other functions such as bit error rate estimation. The CRC-4 multiframe consists of
16 basic frames numbered 0 to 15, and has a repetition rate of 16 frames X 125 microseconds/frame = 2 msec.
CRC-4 multiframe alignment is based on the 001011 bit sequence, which appears in bit position one of the first six
NFASs of a CRC-4 multiframe.
The CRC-4 multiframe is divided into two submultiframes, numbered 1 and 2, which are each eight basic frames or
2048 bits in length.
The CRC-4 frame alignment verification functions as follows. Initially, the CRC-4 operation must be activated and
CRC-4 multiframe alignment must be achieved at both ends of the link. At the local end of a link, all the bits of every
transmit submultiframe are passed through a CRC-4 polynomial (multiplied by X
generates a four bit remainder. This remainder is inserted in bit position one of the four FASs of the following
submultiframe before it is transmitted (see Table 12).
CRC-4
E1 CRC-4 Multiframing (Timeslot 0)
multiframe alignment signal.
indicates position of CRC-4
Frame/Type
13/NFAS
15/NFAS
11/NFAS
1/NFAS
3/NFAS
5/NFAS
7/NFAS
9/NFAS
10/FAS
12/FAS
14/FAS
CRC-4
0/FAS
2/FAS
4/FAS
6/FAS
8/FAS
Table 12 - CRC-4 FAS and NFAS Structure (E1)
Zarlink Semiconductor Inc.
C
C
C
C
C
C
C
E
C
E
1
0
0
1
0
1
1
1
2
3
4
1
2
3
1
4
2
MT9072
2
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
50
A
A
A
A
A
A
A
A
3
0
0
0
0
0
0
0
0
S
S
S
S
S
S
S
S
PCM30 Channel Zero
4
1
1
1
1
1
1
1
1
a4
a4
a4
a4
a4
a4
a4
a4
S
S
S
S
S
S
S
S
5
1
1
1
1
1
1
1
1
a5
a5
a5
a5
a5
a5
a5
a5
4
then divided by X
S
S
S
S
S
S
S
S
6
0
0
0
0
0
0
0
0
a6
a6
a6
a6
a6
a6
a6
a6
S
S
S
S
S
S
S
S
4
7
1
1
1
1
1
1
1
1
a7
a7
a7
a7
a7
a7
a7
a7
+ X + 1), which
Data Sheet
S
S
S
S
S
S
S
S
8
1
1
1
1
1
1
1
1
a8
a8
a8
a8
a8
a8
a8
a8