MT8979AC Просмотр технического описания (PDF) - Mitel Networks
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MT8979AC Datasheet PDF : 26 Pages
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MT8979 ISO-CMOS
The multiframe synchronization algorithm is
dependent upon the state of frame alignment framer.
The multiframe framer will not initiate a search for
multiframe synchronization until frame sync is
achieved. Multiframe synchronization will be
declared on the first occurrence of four consecutive
zeros in the higher order quartet of channel 16.
Once multiframe synchronization is achieved, the
framer will only go out of synchronization after
detection of two errors in the multiframe signal or
loss of frame alignment synchronization.
The CRC synchronization algorithm is also
dependent on the state of the frame alignment
framer, but is independent of the multiframe
synchronization. The CRC framer will not initate a
search for CRC framing signal until frame alignment
synchronization is achieved. Once frame alignment
synchronization is acquired, the CRC framer must
find two framing signals in bit 1 of the non-frame
alignment signal. Upon detection of the second CRC
framing signal the MT8979 will immediately go into
CRC synchronization. When maintenance feature is
enabled (maint bit = 1) the CRC framer will force a
complete reframe of the device if CRC frame
synchronization is not found within 8 ms or more
than 914 CRC errors occur per second.
time out > 8ms
number of CRC
errors > 914/s
find two CRC
frame alignment
signals
Yes
CRC synchronization
acquired
- - - - - Only if the
maintenance
option is
selected
out of
synchronization
No
search for frame
alignment
signal
No
Yes
verify bit 2 of non-
frame alignment
signal
Yes
No
verify second
occurrence of frame
alignment signal
Yes
frame synchroni-
zation acquired
# of consecutive incorrect
frame alignment signals = 3
No
search for
multiframe align-
ment signal
Yes
multiframe synchro-
nization acquired
Yes
check for two errored
multiframe alignment
signals
No
Figure 13 - Synchronization State Diagram
4-170
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