MT9074 Просмотр технического описания (PDF) - Zarlink Semiconductor Inc

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MT9074

T1/E1/J1 Single Chip Transceiver

Zarlink Semiconductor Inc 

MT9074

Data Sheet

PCM30

Timeslots

0 1,2,3...15 16 17,18,19,... 31

Voice/Data

Channels

(DSTi/o

and

CSTi/o)

0 1,2,3...15 16 17,18,19,... 31

Table 10 - STBUS vs. PCM-30 to Channel Relationship(E1)

Basic Frame Alignment

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).

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.

Bits four to eight of the NFAS (i.e., Sa4 - Sa8) are additional spare bits which may be used as follows:

• Sa4 to Sa8 may be used in specific point-to-point applications (e.g., transcoder equipments conforming to

G.761)

• Sa4 may be used as a message-based data link for operations, maintenance and performance monitoring

• Sa5 to Sa8 are for national usage

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.

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.

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.

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Zarlink Semiconductor Inc.

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