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Data Alignment Configurations
• If the 8B/10B encoder is enabled (TBIE = low), alignment is also lost when the
number of received code groups with 8B/10B coding errors outnumbers the
non-errored code groups by four. Credit for non-errored code groups in excess of
errored code groups is limited to four, such that alignment is lost after four
consecutive errored code groups. The receiver restarts its alignment procedure and
halts data flow until alignment is achieved.
• Finally, the user may force loss of alignment by asserting XCVR
(high). Each receiver may thus be forced to restart its alignment procedure. Data
flow will halt until alignment is achieved. Normally, XCVR
disable the transmitter. If this is not desired, raising DROP_SYNC concurrent with
(or prior to) XCVR
effect on the corresponding transmitter.
Since XCVR_x_DISABLE and DROP_SYNC are not
synchronous to the internal clock domain DROP_SYNC
should be raised prior to XCVR_x_DISABLE is raised and
remain high until after XCVR_x_DISABLE is negated low.
When establishing byte alignment, or when data flow is halted due to misalignment, the
'Not Byte Sync' error is reported as described in Section 3.7.3, "Error Handling."
3.5.3
Word Synchronization
When the MC92603 is configured in either of the 'aligned backplane' modes (BSYNC high
and COMPAT low), the four receivers can be used cooperatively to receive 32-bit (40-bit
if TBIE is high) aligned word transfers. Word alignment is enabled by asserting the word
synchronization enable inputs, WSYNC1 or WSYNC0, high.
3.5.3.1
Word Synchronization Method
The word synchronization aligns code groups in the receiver's alignment FIFO.
Synchronization is accomplished by lining up word synchronization events detected by
each of the receivers, such that all are coincident at the same output stage of their FIFO.
There are three word synchronization events as defined in Table 3-6.
Word Synchronization Event
No word synchronization required
4 IDLE/1 non-IDLE
Disparity-based IDLE sequence
Align to special control character K28.3 (/A/)
3-10
MC92603 Quad Gigabit Ethernet Transceiver Reference Manual
DISABLE will force the receiver to re-align and have no
_x_
NOTE
Table 3-6. Word Synchronization Events
_x_
DISABLE will also
_x_
WSYNC1
WSYNC0
Low
Low
Low
High
High
Low
High
High
DISABLE
MOTOROLA
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