STANDARD PRODUCT
PM4328 TECT3
DATASHEET
PMC-2011596
ISSUE 1
HIGH DENSITY T1/E1 FRAMER
AND M13 MULTIPLEXER
Table 1: E1-FRMR Framing States
State
Out of Frame Out of Offline Frame
FAS_Find_1
Yes
Yes
Yes
No
No
No
No
No
No
No
No
No
No
No
No
Yes
Yes
Yes
No
No
NFAS_Find
FAS_Find_2
BFA
CRC to CRC Interworking
FAS_Find_1_Par
NFAS_Find_Par
FAS_Find_2_Par
BFA_Par
CRC to non-CRC Interworking
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 1.
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
is declared and the basic frame alignment is set accordingly (i.e., the basic frame
alignment is set to correspond to the frame alignment found by the parallel offline
search, which is also the basic frame alignment corresponding to the newly
found CRC multiframe alignment).
Subsequent expirations of the 8 ms timer will likewise reinitiate a new search for
basic frame alignment. If, however, the 400 ms timer expires at any time during
this procedure, the E1-FRMR stops searching for CRC multiframe alignment and
declares CRC-to-non-CRC interworking. In this mode, the E1-FRMR may be
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PMC [ PMC-SIERRA, INC ]
