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Preliminary Data Sheet
October 2000
TFRA08C13 OCTAL T1/E1 Framer
46
L Lucent Technologies Inc.
Frame Formats
(continued)
CEPT 2.048 Basic Frame Structure
The ITU Rec. G.704 Section 2.3.1 defined frame length is 256 bits, numbered 1 to 256. The frame repetition rate is
8 kHz. The allocation of bits numbered 1 to 8 of the frame is shown in Table 19.
Table 19. Allocation of Bits 1 to 8 of the FAS Frame and the NOT FAS Frame
The function of each bit in Table 19 is described below:
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The Si bits are reserved for international use. A specific use for these bits is described in Table 20. ITU CRC-4
Multiframe Structure. If no use is realized, these bits should be fixed at 1 on digital paths crossing an interna-
tional border.
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Bit 2 of the NOT FAS frames is fixed to 1 to assist in avoiding simulations of the frame alignment signal.
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Bit 3 of the NOT FAS is the remote alarm indication (A bit). In undisturbed operation, this bit is set to 0; in alarm
condition, set to 1.
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Bits 4—8 of the NOT FAS (Sa4—Sa8) may be recommended by ITU for use in specific point-to-point applica-
tions. Bit Sa4 may be used as a message-based data link for operations, maintenance, and performance moni-
toring. If the data link is accessed at intermediate points with consequent alterations to the Sa4 bit, the CRC-4
bits must be updated to retain the correct end-to-end path termination functions associated with the CRC-4 pro-
cedure. The receive framer does not implement the CRC-4 modifying algorithm described in ITU Rec. G.706
Annex C. Bits Sa4—Sa8, where these are not used, should be set to 1 on links crossing an international border.
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MSB = most significant bit and is transmitted first.
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LSB = least significant bit and is transmitted last.
Basic Frames
Bit 1 (MSB)
Si
Si
Bit 2
0
1
Bit 3
0
A
Bit 4
1
Sa4
Bit 5
1
Sa5
Bit 6
0
Sa6
Bit 7
1
Sa7
Bit 8 (LSB)
1
Sa8
Frame Alignment Signal (FAS)
Not Frame Alignment Signal
(NOT FAS)