Altera Corporation
2–81
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
The
rx_bitslip
is disabled at time
n
+ 3 and re-enabled at time
n
+ 4.
The output of the
rx_dataout
now matches the specified alignment
pattern, thus the
rx_patterndetect
signal is asserted for one clock
cycle. At time
n
+ 5, the
rx_patterndetect
signal is still asserted
because the alignment pattern still exists in the current word boundary.
Finally, at time
n
+ 6 the
rx_dataout
boundary is shifted again and the
rx_patterndetect
signal is deasserted to signify that the word
boundary does not contain the alignment pattern.
Figure 2–63. Word Aligner Symbol Interaction in Manual Bit-Slip Mode
Synchronization State Machine Mode
In single-width mode, you can choose to have the link synchronization
handled by a state machine. Unlike the manual alignment mode where
there is no built-in hysteresis to go into or fall out of synchronization, the
synchronization state machine offers automatic detection of a valid
number of alignment patterns and synchronization and detection of code
group errors for automatically falling out of synchronization. The
synchronization state machine is available in the Basic (single-width
mode only), XAUI, GIGE, and PIPE modes. For the XAUI, GIGE, and
PIPE modes, the number of alignment patterns, consecutive code groups,
and bad code groups are fixed. You must use the 8B/10B code for the
synchronization state machine. In XAUI, GIGE, and PIPE modes, the
8B/10B encoder/decoder is embedded in the transceiver data path. In
Basic single-width mode, you can configure the MegaWizard to either use
or bypass the 8B/10B encoder/decoder in the transceiver. If the
synchronization state machine is enabled and the 8B/10B
encoder/decoder is bypassed, the 8B/10B encoder/decoder logic must
be implemented outside the transceiver as a requirement for using the
synchronization state machine.
rx_clkout
rx_datain
rx_dataout[7..0]
rx_bitslip
rx_patterndetect
n
n + 1
n + 2
n + 3
n + 4
n + 5
n + 6
11110000
01111000
00111100
00011110
00001111