190
Virtex-5 RocketIO GTP Transceiver User Guide
UG196 (v1.3) May 25, 2007
Chapter 8:
Cyclic Redundancy Check (CRC)
R
The CRC Primitive
Each CRC block computes a 32-bit CRC using the CRC32 polynomial specified for PCI
Express, Gigabit Ethernet, and other common protocols. The CRC32 polynomial is:
Equation 8-1
There are two primitives for instantiating CRC integrated blocks. The 32-bit CRC primitive
(CRC32) can process 8, 16, 24, or 32-bit input data and generates a 32-bit CRC. The 64-bit
primitive (CRC64) can process 8, 16, 24, 32, 40, 56, or 64-bit input data and also generates a
32-bit CRC. Using the CRC64 primitive consumes both CRC integrated blocks paired with
a given transceiver tile.
For CRC64, CRCDATAWIDTH is interpreted as indicated in
G X
( )
X
32
X
26
X
23
X
22
X
16
X
12
X
11
X
10
X
8
X
7
X
5
X
4
X
2
X
1
+
+
+
+
+
+
+
+
+
+
+
+
+
+
=
Table 8-4:
CRC32 – Valid Data Widths
CRCDATAWIDTH[2:0]
Data Width
CRC Data Bus Bits
000
8-bit
CRCIN[31:24]
001
16-bit
CRCIN[31:16]
010
24-bit
CRCIN[31:8]
011
32-bit
CRCIN[31:0]
Notes:
1. CRCDATAWIDTH[2] must ALWAYS be set to 0 for the CRC32 primitive.
Table 8-5:
CRC64 – Valid Data Widths
CRCDATAWIDTH[2:0]
Data Width
CRC Data Bus Bits
000
8-bit
CRCIN[63:56]
001
16-bit
CRCIN[63:48]
010
24-bit
CRCIN[63:40]
011
32-bit
CRCIN[63:32]
100
40-bit
CRCIN[63:24]
101
48-bit
CRCIN[63:16]
110
56-bit
CRCIN[63:8]
111
64-bit
CRCIN[63:0]
Содержание Virtex-5 RocketIO GTP
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Страница 256: ...256 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Section 3 Appendices R...
Страница 312: ...312 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Appendix E Low Latency Design R...