BT8376EPF datasheet(187/323 Pages) CONEXANT

187 / 323 page

Bt8370/8375/8376

Fully Integrated T1/E1 Framer and Line Interface

3.12 Transmitter Registers

N8370DSE

Conexant

3-69

Table 3-17. Criteria for E1 Loss/Recovery of Transmit Frame Alignment

Mode

Description

FAS

Basic Frame Alignment (BFA) is recovered when the following search criteria are satisfied:

•

FAS pattern (0011011) is found in frame N.

•

Frame N+1 contains bit 2 equal to 1.

•

Frame N+2 also contains FAS pattern (0011011).

During FAS only modes, BFA is recovered when the following search criteria is satisfied:

•

FAS pattern (0011011) is found in frame N.

•

No mimics of the FAS pattern present in frame N+1.

•

FAS pattern (0011011) is found in frame N+2.

NOTE(S):

If FAS pattern is not found in frame N+2 or FAS mimic is found in frame N+1, the search restarts in

frame N+2.

Transmit Loss of Frame (TLOF) alignment is declared when:

Three consecutive FAS pattern errors are detected, when the FAS pattern consists of a 7-bit (x0011011)

pattern in FAS frames, as well as bit 2 equaling 1 in NFAS frames.

MFAS

MFAS—CRC Multiframe Alignment is recovered when the following search criteria are satisfied:

•

BFA is recovered, identifying FAS and NFAS frames.

•

Within 6 ms after BFA, bit 1 of NFAS frames contains the first MFAS pattern (001011xx).

•

Within 8 ms after BFA, bit 1 of NFAS frames contains the second MFAS pattern (001011xx), aligned

to first MFAS.

MFAS errors do not cause Transmit Loss of Frame (TLOF) alignment.

CAS

CAS Multiframe Alignment is recovered when the following search criteria are satisfied:

•

BFA is recovered, identifying TS0 through TS31.

•

MAS (0000xxxx) Multiframe Alignment Signal pattern is found in the first 4 bits of TS16, and 8 bits

of TS16 in preceding frame contains nonzero value.

CAS errors do not cause Transmit Loss of Frame (TLOF) alignment.

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