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MT9074AL 参数 Datasheet PDF下载

MT9074AL图片预览
型号: MT9074AL
PDF下载: 下载PDF文件 查看货源
内容描述: T1 / E1 / J1单芯片收发器 [T1/E1/J1 Single Chip Transceiver]
分类和应用: 电信集成电路
文件页数/大小: 122 页 / 371 K
品牌: MITEL [ MITEL NETWORKS CORPORATION ]
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Advance Information  
MT9074  
Basic Frame Alignment  
PCM 30 Channel Zero  
CRC  
Frame/  
Type  
CRC  
Time slot 0 of every basic frame is reserved for basic  
frame alignment and contains either a Frame  
Alignment Signal (FAS) or a Non-Frame Alignment  
Signal (NFAS). FAS and NFAS occur in time slot zero  
of consecutive basic frames as shown in Table 12.  
Bit two is used to distinguish between FAS (bit two =  
0) and NFAS (bit two = 1).  
1
C1  
0
2
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
3
0
4
5
6
7
8
0/FAS  
1
1
0
1
1
1/NFAS  
2/FAS  
A
0
Sa4 Sa5 Sa6 Sa7 Sa8  
C2  
0
1
1
0
1
1
3/NFAS  
4/FAS  
A
0
Sa4 Sa5 Sa6 Sa7 Sa8  
C3  
1
1
1
0
1
1
Basic frame alignment is initiated by a search for the  
bit sequence 0011011 which appears in the last  
seven bit positions of the FAS, see the Frame  
Algorithm section. Bit position one of the FAS can be  
either a CRC-4 remainder bit or an international  
usage bit.  
5/NFAS  
6/FAS  
A
0
Sa4 Sa5 Sa6 Sa7 Sa8  
C4  
0
1
1
0
1
1
7/NFAS  
8/FAS  
A
0
Sa4 Sa5 Sa6 Sa7 Sa8  
C1  
1
1
1
0
1
1
9/NFAS  
10/FAS  
11/NFAS  
12/FAS  
A
0
Sa4 Sa5 Sa6 Sa7 Sa8  
Bits four to eight of the NFAS (i.e., Sa4 - Sa8) are  
additional spare bits which may be used as follows:  
C2  
1
1
1
0
1
1
A
0
Sa4 Sa5 Sa6 Sa7 Sa8  
S
to S may be used in specific point-to-point  
a4 a8  
C3  
1
1
0
1
1
applications (e.g. transcoder equipments  
conforming to G.761).  
13/NFAS E1  
14/FAS C4  
15/NFAS E2  
A
0
Sa4 Sa5 Sa6 Sa7 Sa8  
1
1
0
1
1
S
may be used as a message-based data link  
a4  
for operations, maintenance and performance  
monitoring.  
A
Sa4 Sa5 Sa6 Sa7 Sa8  
Table 11 - FAS and NFAS Structure  
S
to S are for national usage.  
a8  
a5  
indicates position of CRC-4 multiframe alignment signa  
A maintenance channel or data link at 4,8,12,16,or  
20 kHz for selected Sa bits is provided by the  
MT9074 in E1 mode to implement these functions.  
Note that for simplicity all Sa bits including Sa4 are  
collectively called national bits throughout this  
document.  
CRC-4 Multiframing in E1 mode  
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.  
Bit three (designated as “A”), the Remote Alarm  
Indication (RAI), is used to indicate the near end  
basic frame synchronization status to the far end of a  
link. Under normal operation, the A (RAI) bit should  
be set to 0, while in alarm condition, it is set to 1.  
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.  
Bit position one of the NFAS can be either a CRC-4  
multiframe alignment signal, an E-bit or an  
international usage bit. Refer to an approvals  
laboratory and national standards bodies for specific  
requirements.  
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  
X4 then divided by X4 + X + 1), which generates a  
four bit remainder. This remainder is inserted in bit  
17  
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