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Altera Corporation
Stratix II GX Device Handbook, Volume 2
October 2007
Receiver Channel Overview
Word Aligner
The word aligner module contains a fully programmable pattern detector
to identify specific patterns within the incoming data stream. The pattern
detector includes recognition support for control code groups for 8B/10B
encoded data and A1A2 or A1A1A2A2-type frame alignment patterns for
scrambled data. Custom alignment patterns are also available. The word
aligner can be bypassed in some functional modes.
In single-width mode, the following word-alignment options are
available:
■
Manual bit-slip mode
■
Manual alignment to 7-, 10-, or 16-bit patterns
■
Synchronization state machine that offers programmable hysteresis
for synchronization.
In double-width mode, the following word-alignment options are
available:
■
Manual bit-slip mode
■
Manual alignment to 7-, 8-, 10-, 16-, 20-, or 32-bit patterns
Channel Aligner (Deskew)
An embedded channel aligner aligns byte boundaries across multiple
channels and synchronizes the data entering the logic array from the
Gigabit transceiver block’s four channels. The Stratix II GX channel
aligner is optimized for a 10-Gigabit Ethernet XAUI four-channel
implementation. The channel aligner includes the control circuitry and
channel alignment character detection defined by the 10-Gigbit
Attachment Unit Interface (XAUI) protocol.
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This block is only available for the XAUI protocol and is
disabled for all other protocols.
Rate Matcher
In CDR-based systems, the clock frequencies of the transmitting and
receiving devices often do not match. This mismatch can cause the data
to transmit at a rate slightly faster or slower than the receiving device can
interpret. The Stratix II GX rate matcher resolves the frequency
differences between the recovered clock and the FPGA logic array clock
by inserting or deleting removable characters from the data stream, as
defined by the transmission protocol, without compromising transmitted