Xilinx RocketIO User Manual page 87

CRC (Cyclic Redundancy Check)
Note that CRC generation for IDLE requires that the transmitted K28.5 be left-justified in the
MGT's internal two-byte data path. Observing the following restrictions assures correct alignment
of the packet delimiters:
•
•
•
INFINIBAND
The Infiniband CRC is the most complex mode, and is not supported in the CRC generator.
Infiniband CRC contains two computation types: an invariant 32-bit CRC, the same as in Ethernet
protocol; and a variant 16-bit CRC, which is not supported in the hard core. Infiniband CRC must be
implemented entirely in the FPGA fabric.
There are also two Infiniband Architecture (IBA) packets, a local and a global. Both of these IBA
packets are shown in
The CRC is calculated with certain bits masked in LRH and GRH, depending on whether the packet
is local or global. The size of these headers is shown in
Table 2-21: Global and Local Headers
RocketIO™ Transceiver User Guide
UG024 (v2.3.2) June 24, 2004
Note:
As noted in Figure
to the 64-byte minimum packet length. For packets that are already 64 bytes or longer, pad bits
are not used.
4-byte data path: K28.5 must appear in TXDATA[31:24] or TXDATA[15:8].
2-byte data path: K28.5 must appear in TXDATA[15:8].
1-byte data path: K28.5 must be strobed into the MGT on rising TXUSRCLK2 only when
TXUSRCLK is High.
Note:
Minimum data length for this mode is defined by the protocol requirements.
Note:
For correct operation of the Gigabit Ethernet CRC function, transmitted and received
frames must comply with the 802.3 specification regarding Gigabit Ethernet. This includes the
preamble maximum length.
Figure
Local IBA
Packet
SOP LRH BTH
Payload
Global IBA
SOP LRH GRH BTH
Packet
LRH Local Routing Header
GRH Global Routing Header
BTH IBA Transport Header
2-25, pad bits are used to assure that the header, data, and CRC total
2-26.
R R R
0 1
Packet
R R
0
Payload
Figure 2-26: Infiniband Mode
Description
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R
Variant CRC
2 3
R R
Variant CRC
1 2 3
Table 2-21.
8 Bytes
40 Bytes
12 Bytes
R
EOP
EOP
UG024_14_020802
Size
87