Bt8370/8375/8376
Fully Integrated T1/E1 Framer and Line Interface
3.12 Transmitter Registers
Table 3-17. Criteria for E1 Loss/Recovery of Transmit Frame Alignment
Mode
Description
Basic Frame Alignment (BFA) is recovered when the following search criteria are satisfied:
FAS
•
•
•
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
CAS
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 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.
N8370DSE
Conexant
3-69
CONEXANT [ CONEXANT SYSTEMS, INC ]
