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FALC
56
PEF 2256 H/E
Functional Description T1/J1
User’s Manual
Hardware Description
151
DS1.1, 2003-10-23
Setting of RC0.SJR the FALC
56 generates and checks the CRC6 bits according to
JT G.706. The CRC6 checksum is calculated including the FS/DL-bits. In synchronous
state CRC6 errors increment an error counter.
CRC6 generation/checking according to JT G.706
5.2.7
72-Frame Multiframe (SLC96 Format, T1/J1)
The 72-multiframe is an alternate use of the FS-bit pattern and is used for carrying data
link information. This is done by stealing some of redundant multiframing bits after the
transmission of the 12-bit framing header (refer to
Figure 37
on page
152
). The position
of A and B signaling channels (robbed bit signaling) is defined by zero-to-one and
one-to-zero transitions of the FS-bits and is continued when the FS-bits are replaced by
the data link bits.
Remote alarm (yellow alarm) is indicated by setting bit 2 to zero in each time slot. An
additional use of the D-bits for alarm indication is user defined and must be done
externally.
5.2.7.1
Synchronization Procedure
In the synchronous state terminal framing (FT-bits) and multiframing (FS-bits of the
framing header) are observed independently. Further reaction on framing errors
depends on the selected synchronization/resynchronization procedure (by bit
FMR2.SSP):
FMR2.SSP = 0: terminal frame and multiframe synchronization are combined
Two errors within 4/5/6 framing bits (by bits FMR4.SSC1/0) of one of the above lead
to the asynchronous state for terminal framing
and
multiframing. Additionally to The
resynchronization procedure starts with synchronizing upon the terminal framing. If
the pulse framing has been regained, the search for multiframe alignment is initiated.
Multiframe synchronization has been regained after two consecutive correct
multiframe patterns have been received.
FMR2.SSP = 1: terminal frame and multiframe synchronization are separated
Two errors within 4/5/6 terminal framing bits lead to the same reaction as described
above for the “combined” mode.
Two errors within 4/5/6 multiframing bits lead to the asynchronous state only for the
multiframing. Loss of multiframe alignment is reported by bit FRS0.LMFA. The state
of terminal framing is not influenced.
Now, the resynchronization procedure includes only the search for multiframe
alignment. Multiframe synchronization has been regained after two consecutive
correct multiframe patterns have been received.