2–84
Altera Corporation
Stratix II GX Device Handbook, Volume 2
October 2007
Receiver Modules
When either XAUI or GIGE mode is used, the synchronization and word
alignment is handled automatically by a built-in state machine that
adheres to either the IEEE 802.3ae or IEEE 802.3 synchronization
specifications, respectively. If you specify either standard, the alignment
pattern is automatically defaulted to /K28.5/ (b'0011111010).
When you specify the XAUI protocol, code-group 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 allowed 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 or
“XAUI
Mode” on page 2–167
for more information regarding the operation of
the synchronization phase.
If you specify the GIGE protocol, code-group synchronization is achieved
upon the reception of three consecutive ordered sets. An ordered set
starts with the /K28.5/ comma and can be followed by an odd number of
valid data code groups. Invalid code groups are not allowed during the
reception of three ordered-sets. When code-group synchronization is
achieved the optional
rx_syncstatus
signal is asserted.
In PIPE mode, lane synchronization is achieved when the word aligner
sees 4 good /K28.5/ commas and 16 good code groups. This is
accomplished through the reception of 4 good PCI Express training
sequences (TS1 or TS2). The PCI-Express fast training sequence (FTS) can
also be used to achieve lane or link synchronization, but requires at least
five of these training sequences. The
rx_syncstatus
signal is asserted
when synchronization is achieved and is deasserted when the word
aligner receives 23 code group errors.
Double-Width Mode
In the double-width mode, there are two blocks active in the word
aligner: the pattern detector and manual alignment mode. The pattern
detector detects if the pattern exists in the current word boundary. The
manual alignment identifies the alignment pattern across the byte
boundaries and aligns to the correct byte boundary. There are no
synchronization state machines available for the double-width mode.