VSC7216-02
Data Sheet
page 17. The RESYNC state is entered when a 10-bit word has been received that contains the 7-bit Comma pattern
(e.g. a K28.5 IDLE character). After entering the RESYNC state, the VSC7216-02 will stay in it until a valid,
non-Comma transmission is received, then it transitions to the SYNC_ACQUIRED state indicating a normal
operating condition. The RESYNC state is re-entered if four consecutive Commas are received or if a single Comma
is received that changes the 10B character framing boundary. The LOSS_OF_SYNC state is entered whenever four
consecutive invalid transmissions have been detected or when the occurrences of invalid transmission outnumber
those of valid transmission by four. The relative occurrences of invalid versus valid transmissions are monitored with
a simple up/down counter that increments when an invalid transmission is detected and decrements otherwise. The
LSSM transitions to the LOSS_OF_SYNC state when the counter reaches four, and the counter is reset. A state
diagram for the invalid transmission counter is shown in Figure 12 on page 18. The VSC7216-02 receiver will stay in
the LOSS_OF_SYNC state until a valid Comma pattern is detected. Note that the RESYNC state is entered whenever
the 10B framing boundary is changed, and whenever the Word Sync Sequence is received. When ENDEC is LOW the
ERRn, KCHn and IDLEn outputs are re-defined and the decoder and associated LSSM logic in each channel is
unused.
Valid Comma
(K28.1, K28.5, K28.7)
RESYNC
ERRn=1
KCHn=1
IDLEn=1
Valid Non-Comma
Valid Comma
Invalid Transmission
Four Consecutive Commas
or
Mis-Aligned Comma
Four Consecutive
LOSS_OF_SYNC
SYNC_ACQUIRED
Invalid Transmissions
or
ERRn=1
KCHn=1
IDLEn=0
ERRn=0
KCHn=X
IDLEn=X
ERRn=1
KCHn=0
IDLEn=X
or
Invalid minus Valid
Transmissions is > 4
Figure 11. State Diagram of the Loss of Synchronization State Machine
17 of 40
G52367 Revision 4.2
December 2006
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
