Sonet Alignment - Xilinx Virtex-4 RocketIO User Manual

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SONET Alignment

Virtex-4 MGTs support bit and byte alignment for SONET A1A2 transitions for line rates of
OC12 (12 A1s followed by 12 A2s). The SONET aligner operates on byte-aligned data and
relies on the standard byte aligner described in the previous section to perform alignment
to byte boundaries.
the COMMA32 attribute TRUE selects the output of the SONET Aligner. The SONET
aligner can only be used with a 32-bit internal datapath selected by RXINTDATAWIDTH =
2'b10.
rxdata_unaligned[31:0]
Figure 3-15
example, the receiver is not yet aligned and is receiving 0s until the unaligned sequence of
A1A1A1A1A2A2A2A2 followed by 0s is received. Within the 32-bit words, the received
data order is LSb to MSb.
rxdata_sonet_aligned[31:0]
Virtex-4 RocketIO MGT User Guide
UG076 (v4.1) November 2, 2008
Figure 3-14
Unaligned
Byte
Aligner
Figure 3-14: SONET Alignment Data Flow
exemplifies how the byte and SONET aligners work in combination. For this
RXUSRCLK2
rxdata_unaligned[31:0]
Unaligned A1A1A1A1A2A2A2A2 pattern =
rxdata_byte_aligned[31:0]
Figure 3-15: SONET Alignment Sequence (4-Byte External Data Interface Width)
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Symbol Alignment and Detection (Comma Detection)
shows the data flow of the receive alignment logic. Setting
Byte
Aligned
rxdata_byte_aligned[31:0] SONET
Aligner
0x 0x 0x 0x
8000 BCBD 5050 0000
0000 BDBD 5050 0000
0x6F6F6F6F14141414,
0x
6F00
0000
Byte-aligned A1A1A1A1A2A2A2A2 pattern =
SONET
RXCOMMADETUSE
Aligned
COMMA32
rxdata_sonet_aligned[31:0]
1
0
ug076_ch3_35_032006
offset by 2 bits
0x 0x 0x
146F 0014 0000
6F6F 1414 0000
0x6F6F6F6F14141414
0x 0x 0x
6F6F 1414 0000
6F6F 1414 0000
Word-aligned A1A1A2A2 boundary
ug076_ch3_36_061907
1
0
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