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MT9072
Data Sheet
54
Zarlink Semiconductor Inc.
Figure 7 - Synchronization State Diagram (E1)
6.0 Elastic Buffer
The MT9072 has a two frame receive elastic (or slip) buffer, which absorbs wander and low frequency jitter in
multi-trunk applications. If desired, the elastic buffer can be bypassed by using the Data Link RxDL pin output (see
the following section). The received data (RPOS and RNEG) is clocked into the elastic buffer with the extracted
(EXCLi pin) clock and is clocked out of the elastic buffer with the system (CKi pin) clock. The EXCLi clock is
generated from the receive data, and is therefore phase-locked with that data. In normal operation, the EXCLi clock
400 msec timer expired
>914 CRC errors
in one second
NO
3 consecutive incorrect
frame alignment
signals
YES
CRC-to-non-CRC interworking. Maintain
primary basic frame alignment. Continue
to send CRC-4 data, but stop CRC
processing. E-bits set to ‘0’. Indicate
CRC-to-non-CRC operation. Note 7.
Search for primary basic
frame alignment signal
RAI=1, Es=0.
Out of synchronization
Verify Bit 2 of non-frame
alignment signal.
Parallel search for new basic
frame alignment signal.
Notes 6 & 7.
YES
YES
NO
CRC multiframe
alignment
* only if CRC-4 synchronization is selected and
automatic CRC-4 interworking is de-selected.
** only if automatic CRC-4 interworking is selected.
8 msec. timer
expired**
CRC-to-CRC interworking. Re-align to new
basic frame alignment. Start CRC-4
processing. E-bits set as per G.704 and
I.431. Indicate CRC synchronization
achieved.
Notes 7 & 8.
signaling multi-frame
alignment
Primary basic frame
synchronization acquired. Enable
traffic RAI=0, E’s=0. Start loss of
primary basic frame alignment
checking. Notes 7 & 8.
YES
CRC-4 multi-frame
alignment
YES
Verify second
occurrence of frame
alignment signal.
Start 8 msec timer.
Note 7.
Multiframe synchronization
acquired as per G.732.
Note 7.
Find two CRC frame
alignment signals.
Note 7.
Check for two consecutive errored
multiframe alignment signals.
Notes 7 & 8.
Start 400 msec timer.
Note 7.
Search for multiframe
alignment signal.
Note 7.
NO
NO
NO
YES
Basic frame
alignment acquired
No CRC
multiframe
alignment.
No CRC multiframe
alignment.
8 msec. timer
expired*
RAI = 0