Altera Corporation
2–71
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
Word Aligner
The word aligner (refer to
Figure 2–57
) is part of the Stratix II GX
transceiver digital blocks and is located in the receiver path between the
deserializer and the de-skew FIFO buffer. The word aligner restores the
byte boundary of the upstream transmitter based on a programmable
alignment pattern that appears in the serial data stream.
Figure 2–57. Word Aligner
The word aligner block consists of four main sub-blocks:
■
Aligner block
■
Pattern detect block
■
Manual bit-slip block
■
Run-length checker
There are three modes in which the word aligner works: single-width
mode, double-width mode, and automatic synchronization state machine
mode. The following sections explain each of the blocks in each mode of
operation. The word aligner cannot be bypassed and must be used.
However, you can use the
rx_enapatternalign
port to set the word
alignment to not align to the pattern.
Single-Width Mode
In single-width mode, there are three blocks active in the word aligner:
■
Pattern detector
■
Manual word aligner
■
Automatic synchronization state machine
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. The
synchronization state machine detects the number of alignment patterns
and good code groups for synchronization and goes out of
Word
Aligner
datain
dataout
bitslip
enapatternalign
syncstatus
patterndetect
clock
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