Altera Corporation
2–89
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
on the
rx_enapatternalign
signal, the word aligner starts looking for
the 10-bit word alignment pattern again and asserts the
rx_syncstatus
signal once it finds the 10-bit alignment pattern. The
rx_enapatternalign
port only operates in an edge-sensitive fashion
in double-width mode. You must deassert the
rx_enapatternalign
signal and assert it again for re-alignment. Altera recommends using the
/K28.5/ code group as one of the control codes for this alignment pattern.
For example, assume that 8B/10B coding is used and a /+D19.1/
(b'110010 1001) character is specified as the alignment pattern. In that
case, a false word boundary is detected if a /-D15.1/ (b'010111 1001) is
followed by a /+D18.1/ (b'010011 1001). Refer to
Figure 2–67
.
Figure 2–67. False Word Boundary Alignment if Alignment Pattern Exists Across Word Boundaries, Double
Width
If there is no rising edge on the
rx_enapatternalign
port, the current
word boundary is locked, even if the alignment pattern is detected across
different boundaries.
Figure 2–68
shows an example of how the word aligner signals interact in
10-bit alignment mode. For this example, a /K28.5/ (10'b0011111010) is
specified as the alignment pattern. The
rx_enapatternalign
signal is
as a rising edge at time
n
, alignment occurs whenever an alignment
pattern exists in the pattern. The
rx_patterndetect
signal is asserted
for one clock cycle to signify that the pattern exists on the re-aligned
boundary. The
rx_syncstatus
signal also gets asserted to signify that
the boundary has been synchronized. At time
n
+ 1, the
rx_enapatternalign
signal is deasserted and no rising edge occurs,
which instructs the word aligner to lock the current word boundary. The
alignment pattern is detected at time
n
+ 2, but it exists on a different
boundary than the current locked boundary.
Figure 2–68
shows that the
alignment pattern exists across time
n
+ 1 and
n
+ 2. In this condition the
rx_patterndetect
signal remains low because the alignment pattern
does not exist on the current word boundary. It is up to the user logic to
decide whether or not to assert the
rx_enapatternalign
signal to
re-initiate the word alignment process. At time
n
+ 3, the
rx_patterndetect
signal is asserted for one clock cycle to signify that
…..
…..
0
1
0
1
1
1
1
0
0
1
0
1
0
0
1
1
1
0
0
1
-
D15.1
+D18.1
+D19.1