STANDARD PRODUCT
PM4351 COMET
DATA SHEET
PMC-1970624
ISSUE 10
COMBINED E1/T1 TRANSCEIVER
Table 15
- E1-FRMR Framing States
State
Out of Frame Out of Offline Frame
FAS_Find_1
Yes
Yes
Yes
No
No
No
NFAS_Find
FAS_Find_2
No
BFA
No
CRC to CRC Interworking
FAS_Find_1_Par
NFAS_Find_Par
FAS_Find_2_Par
BFA_Par
No
No
No
Yes
Yes
Yes
No
No
No
No
CRC to non-CRC Interworking
No
No
The states of the primary basic framer and the parallel/offline framer in the
E1-FRMR block at each stage of the CRC multiframe alignment algorithm are
shown in Table 15.
From an out of frame state, the E1-FRMR attempts to find basic frame alignment
in accordance with the FAS/NFAS/FAS G.706 Basic Frame Alignment procedure
outlined above. Upon achieving basic frame alignment, a 400 ms timer is
started, as well as an 8 ms timer. If two CRC multiframe alignment signals
separated by a multiple of 2 ms are observed before the 8 ms timer has expired,
CRC multiframe alignment is declared.
If the 8 ms timer expires without achieving multiframe alignment, a new offline
search for basic frame alignment is initiated. This search is performed in
accordance with the Basic Frame Alignment procedure outlined above.
However, this search does not immediately change the actual basic frame
alignment of the system (i.e., PCM data continues to be processed in
accordance with the first basic frame alignment found after an out of frame state
while this frame alignment search occurs as a parallel operation).
When a new basic frame alignment is found by this offline search, the 8 ms timer
is restarted. If two CRC multiframe alignment signals separated by a multiple of
2 ms are observed before the 8 ms timer has expired, CRC multiframe alignment
PROPRIETARY AND CONFIDENTIAL
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