EP2SGX60CF780C4N Datasheet, PDF (29/316 Pages) Altera Corporation – Support for numerous single-ended and differential I/O standards

Stratix II GX Architecture
This module detects word boundaries for the 8B/10B-based protocols,
SONET, 16-bit, and 20-bit proprietary protocols. This module is also used
to align to specific programmable patterns in PRBS7/23 test mode.
Pattern Detection
The programmable pattern detection logic can be programmed to align
word boundaries using a single 7-, 8-, 10-, 16-, 20, or 32-bit pattern. The
pattern detector can either do an exact match, or match the exact pattern
and the complement of a given pattern. Once the programmed pattern is
found, the data stream is aligned to have the pattern on the LSB portion
of the data output bus.
XAUI, GIGE, PCI Express, and Serial RapidIO standards have embedded
state machines for symbol boundary synchronization. These standards
use K28.5 as their 10-bit programmed comma pattern. Each of these
standards uses different algorithms before signaling symbol boundary
acquisition to the FPGA.
The pattern detection logic searches from the LSB to the most significant
bit (MSB). If multiple patterns are found within the search window, the
pattern in the lower portion of the data stream (corresponding to the
pattern received earlier) is aligned and the rest of the matching patterns
are ignored.
Once a pattern is detected and the data bus is aligned, the word boundary
is locked. The two detection status signals (rx_syncstatus and
rx_patterndetect) indicate that an alignment is complete.
Figure 2–18 is a block diagram of the word aligner.
Figure 2–18. Word Aligner
datain
bitslip
Word
dataout
Aligner
syncstatus
enapatternalign patterndetect
clock
Altera Corporation
October 2007
2–21
Stratix II GX Device Handbook, Volume 1