mt9074ap1 Zarlink Semiconductor, mt9074ap1 Datasheet - Page 29

• Manufacturer Part Number: mt9074ap1
• Description: T1/e1/j1 Single Chip Transceiver With Wide Dynamic Range Liu
• Manufacturer: Zarlink Semiconductor

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:
•
•
•
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.
S
G.761)
S
S
a4
a4
a5
to S
to S
may be used as a message-based data link for operations, maintenance and performance monitoring
a8
a8
are for national usage
may be used in specific point-to-point applications (e.g., transcoder equipments conforming to
Table 10 - STBUS vs. PCM-30 to Channel Relationship(E1)
PCM30
Timeslots
Voice/Data
Channels
(DSTi/o
and
CSTi/o)
0 1,2,3...15
0 1,2,3...15
Zarlink Semiconductor Inc.
MT9074
29
16
16
17,18,19,... 31
17,18,19,... 31
Data Sheet