Altera Stratix GX Transceiver - Manual (Page 119)

Altera Corporation 5–7
January 2005 Stratix GX Transceiver User Guide
XAUI Mode
This module matches the 10-bit comma specified in the MegaWizard ®
Plug-In Manager with the data and its complement in the current word
boundary. Both positive and negative disparities are checked in this
mode. For example, if a /K28.5/ (b'0011111010) pattern is specified as
the comma, the rx_patterndetect signal is asserted if
b'0011111010
or b'1100000101 is detected in the incoming data.
XAUI uses an embedded clocking scheme that re-times the data, which
can also alter the code-group boundary. The boundaries of the
code-groups are realigned through a synchronization process specified in
clause 48 of the IEEE 802.3ae standard, which states that synchronization
is achieved upon the reception of four /K28.5/ commas. Each comma can
be followed by any number of valid code-groups. Invalid code-groups are
not supported during the synchronization stage.
XAUI Synchronization Mode
When a Stratix GX transceiver is configured to the XAUI protocol, the
built-in pattern detector, word aligner, and XAUI state machines adhere
to the PCS synchronization specification. The code-group
synchronization is achieved upon the reception of four /K28.5/ commas.
Each comma is followed by any number of valid code-groups. Invalid
code-groups are not supported during the synchronization stage. When
code-group synchronization is achieved, the optional
rx_syncstatus[]
signal is asserted. Refer to clause 47-48 of the IEEE
P802.3ae standard for more information regarding the operation of the
synchronization phase. If the rx_sigdet signal is valid and the reset is
deasserted, the synchronization state machine begins the synchronization
process. If either of the two signals are not valid, the state machine falls
out of the synchronization process and waits for the valid rx_sigdet
signal and reset.
For reference, the PCS synchronization state diagram specified in
clause 48 of the IEEE P802.3ae is shown in
Figure 5–6 .